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The Real Reason Why Oil and Water Don't Mix
Abstract
The majority of introductory chemistry and organic chemistry textbooks state that oil and water don't mix because of enthalpic effects. These texts generally make the argument that the mixing process is endothermic, reasoning that the water-water hydrogen bonds that must be broken in order to accommodate the solute are much stronger than the subsequent solvent-solute dipole-induced dipole intermolecular forces that are formed. In fact, in most cases the mixing process is exothermic, so the immiscibility of the two liquids must be explained by a loss of entropy in the system. The widely accepted model explaining the hydrophobic effect invokes the formation of icelike clathrate hydrate "cages" around nonpolar solute molecules. Water molecules at the surface of these relatively rigid clathrate structures are strongly hydrogen-bonded to one another. The formation of these solvent "cages" explains why both Delta H and Delta S are negative for the solution process, and the endergonicity of solvation is thus due to entropy and not enthalpy. Authors should remove from their textbooks the incorrect enthalpic/hydrogen-bond explanation for the hydrophobic effect. Because aspects of the correct entropic/clathrate "cage" explanation lie beyond the scope of introductory or organic chemistry courses, it may be wisest to omit any detailed physical explanation of the "like dissolves like" phenomenon. If the overall format of the text permits, a brief discussion of solvation entropy effects might be included in the section dealing with the immiscibility of oil and water Keywords (Audience): High School / Introductory Chemistry
... In 1998 I published a paper in the Journal of Chemical Education entitled "The real reason why oil and water don't mix" [1]. In this paper I pointed out that all undergraduate general and organic chemistry textbooks got it wrong when they attempted to explain why oil and water don't mix. ...
... The problem is that when extrapolating results to complex polymer systems, the initial nonpolar phase there is more akin to a liquid, or possibly even a solid [10]. Starting from appropriate standard states (identical number density or molar concentration, e.g., 1 M), both neat/water (reaction 2 in Fig. 1) and oil/water transfer (o/w, reaction 4) are quite similar, 1 and are both studied extensively in the literature. The term hydrophobic interaction is usually reserved for the spontaneous aggregation of nonpolar solutes in aqueous solution, i.e., the reverse of neat/water transfer. ...
... In each reaction, the reactants are two separate phases, water plus an aggregated nonpolar phase, and the product is a single mixed phase: hydrated nonpolar groups in aqueous solution. Insights gathered from the simplest system (i), aqueous solubility of small nonpolar solutes, have been successfully np (o) np (aq) 4. o/w transfer np (g) np (l) np (s) (1) (2) (3) (6) (5) Fig. 1 A nonpolar (np) solute can be transferred into aqueous solution from three different initial phases: (1) from the pure gas phase, hydration; (2) from the pure liquid phase, neat transfer; or (4) from solution in an organic solvent, oil/water (o/w) transfer. A fourth transfer is possible for large nonpolar solutes, from the pure solid phase; this would entail either fusion (6) followed by neat transfer, or organic solvation followed by o/w transfer. ...
Our understanding of the hydrophobic effect has advanced greatly since 1990, with the help of experimental, theoretical, and computer simulation results. The key hydrophobic signature of positive ∆C°P and negative ∆S° at room temperature has been interpreted in light of the importance of solvent cavity creation, solvent-excluded volume, and solute–water intermolecular forces, along with some unusual thermodynamic properties of pure water. Application of the hydrophobic effect to the hydration of small nonpolar solutes, protein folding stability, and protein–ligand binding is discussed in detail in this review, with an emphasis on thermodynamic analyses and interpretations.
... In the case of the water-oil interface, water is a polar molecule, meaning it has a positive and a negative end, which promotes hydrogen bonding among water molecules. Oil, on the other hand, is non-polar and does not have a positive or negative end 53 . This difference in polarity leads the two liquids to layer one on top of the other at the macroscopic scale. ...
... This serves to illustrate the concept of surface tension even in the absence of an external boundary, like air or oil. Water molecules at the surface experience a net inward pull from surrounding water molecules due to hydrogen bonding 45,53 . This inward force is the essence of surface tension. ...
Contemporary approaches to optical multiple micro-manipulation typically involve careful pre-engineering of the laser beam shape. In various biomedical and microfluidic scenarios, especially those necessitating unconventional specimen chambers, there is a demand for controlling the collection of micro-objects at fluid-fluid interfaces. This requirement arises in contexts such as the transport of materials across liquid interfaces for applications like living cell manipulation, drug delivery, soft functional material creation, and various industrial processes. For many of these cases, a regular array of trap sites as well as tightly confinement are not essential. For such applications at interfaces, we expand on the concept of speckle tweezers (ST), which incorporate randomly distributed light fields for quasi-2D optical manipulation. The proposed technique is demonstrated experimentally by applying ST to govern the movement of PS micro-particles at water-oil and water-air interfaces. The efficacy of the method is validated through the temporal characterization of micro-particle motions using digital video microscopy.
... Due to the hydrophobic interaction between water molecules and the -CF 2 -in PVTF, the diffusion of PVTF molecular chains into the aqueous phase will disrupt the hydrogen bond network among water molecules. To compensate for the disrupted hydrogen bonds, water molecules formed additional bonds with adjacent ones, creating "ice-like cage hydrates" [36], which enveloped the PVTF molecular chains in a hydrogen bond network. The PVTF molecular chains tended to reduce their surface area in the aqueous phase, thus folding into nanoparticles. ...
... Due to the hydrophobic interaction between water molecules and the -CF2in PVTF, the diffusion of PVTF molecular chains into the aqueous phase will disrupt the hydrogen bond network among water molecules. To compensate for the disrupted hydrogen bonds, water molecules formed additional bonds with adjacent ones, creating "ice-like cage hydrates" [36], which enveloped the PVTF molecular chains in a hydrogen bond network. The PVTF molecular chains tended to reduce their surface area in the aqueous phase, thus folding into nanoparticles. ...
Electroactive biomaterials can influence the microenvironment between cells and a material’s surface by controlling surface electrical signals, thereby affecting cellular physiological activities. As the most commonly used ferroelectric polymer, Poly(vinylidene fluoride-trifluoroethylene) (PVTF) has attracted widespread attention due to its good stability, biocompatibility and mechanical properties. However, it has limitations such as non-degradability. In this study, PVTF nanoparticles (PVTF NPs), prepared using a phase separation method, were compounded with polylactide (PLA) to prepare PVTF NPs/PLA composite membrane (PN/PLA), which simultaneously achieved electroactivity and degradability. PVTF NPs containing ferroelectric β phase were evenly distributed on the PLA substrate, forming negative potential spots through corona polarization. The PLA substrate gradually degraded in a simulated body fluid environment. The negative surface potential provided by PVTF NPs in PN/PLA enhanced the adhesion, proliferation, and early-stage osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs). The electrical bioactivity and degradability could be joined together in this study, which is promising for tissue regeneration biomaterials, such as guided bone regeneration membrane.
... When mixed, two liquids are miscible when ∆ = ∆ − ∆ < 0. The enthalpic term of mixing ∆ can be either positive or negative for linear alkanes. 148 However, when introducing a non-polar molecule such as an alkane into bulk water, a cavity is formed, causing water molecules to reorganize to a higher organization state around the alkane molecule. This is accompanied by a decrease in entropy and ∆ < 0, which is unfavored. ...
... The importance of the entropic term makes the miscibility unfavored, such as ∆ > 0. This is known as the hydrophobic effect. 148,149 In his model, ...
The multiple aims of this thesis fall within the implementation of a new HT-SMART-FORMU technological platform dedicated to formulation science. The focus is set on the development of reliable experimental methods, theoretical and predictive tools, so as to establish relations between chemical composition, physicochemical properties and applicative properties.The first type of systems investigated in this work consists of solid dispersions. Their stability has long been approached by the DLVO theory, but more recent studies suggest the use of Hansen Solubility Parameters to describe their stability in non-aqueous media. In the first chapter, a systematic analytical method based on zeta potential measurement and light scattering stability monitoring allows deducing a complementarity of both theories to describe the stability of TiO2 dispersions in non-aqueous solvents.The problematic of oil hydrophobicity prediction through EACN values modelling, which is a key parameter to design surfactant/oil/water (SOW) dispersed systems, is addressed in the second chapter. Two mathematical models, designed using machine-learning methods, are proposed for the rapid prediction of the EACN of oils, namely Neural Networks (NN) and Graph Machines (GM). While the GM model is implemented from the SMILES codes, the NN model is fed with σ-moments descriptors computed with the COSMOtherm software. The prediction reliability of both models is discussed based on a complex 10-molecule test set.In chapters 3 and 4, the scope of applicative properties of a nonionic glycerol-based surfactant are investigated. Firstly, chapter 3 focuses on its aggregation behavior in aqueous solutions and the formation of liquid crystals (LC) at low concentration, in comparison with the benchmark polyethoxylated fatty alcohols and alkyl polyglucosides. The influence of its physicochemical properties, in particular the air / water interface dilational viscoelasticity, is put in relation with the observed poor foamability and long-lasting foam stability.Finally, C12Gly2 properties in SOW systems are investigated in chapter 4. The Normalized Hydrophilic-Lipophilic Deviation (HLDN), a powerful theoretical tool, is regarded as a way to rationalize the characteristics of both emulsions and microemulsions. In this way, a thorough quantification of surfactants amphiphilicity, temperature sensitivity and salt-tolerance are presented. The potential use of C12Gly2 as O/W and W/O emulsifier is then investigated: the granulometry and stability of emulsions obtained by varying the oil concurs with HLDN values. A minimum is observed at HLDN = 0 and increases for negative and positive HLDN values.
... The nature of hydrophobicity is still debating and there is no consensus at present. Some scholars believe that the hydrophobic interaction is mainly an entropy effect caused by the destruction of highly dynamic hydrogen bonds between water molecules by non-polar solutes [26,33]. Non-polar regions of hydrocarbon chains or large molecules cannot form hydrogen bonds with water that breaks the hydrogen bond network between water molecules. ...
... The following is a relatively simplified calculation formula proposed by Yoon et al. [34,35]. By analogy with van der Waals force, Yoon et al. proposed that for two-sphere particles, when particle radius R ≫ H, their hydrophobic interaction can be approximated by the following expression [26,33]: ...
The emission of CO2 can be greatly reduced by increasing the solid loading of coal water slurry (CWS) in the gasification industry. In this paper, a mathematic model based on eDLVO and Lifshitz theory is proposed to calculate the interaction between two coal particles and guide the preparation of CWS to increase the solid loading. Lifshitz theory is adopted to calculate the retardation Hamaker constant and van der Waals interaction, which has relatively wide applicability and less assumption. Equations of hydrophobic interaction and electrical double layer are properly simplified with assumptions. It is found that the low rank coal particles in dilute solution are difficult to cross the energy barrier to form aggregations, due to large electrical double layer repulsive interaction. While for bituminous coal, even in dilute solution, the particles will attract with each other. All the coal particles in high concentration CWS will naturally attract with each other to form aggregations, due to higher ion concentration that compressed the electrical double layer with lower absolute value of zeta potential. More energy is dissipated to break the aggregating structure, thus increasing the shear viscosity. Our model can be applied to explain and quantify the influence of ions and pH successfully. For SHH CWS with pH above 9.35, the viscosity of CWS is sharply reduced to 1/3 of original value, which is caused by the greatly increase of the absolute value of zeta potential, as quantified by eDLVO model.
... Hydrophobic interactions refer to the solvent induced interactions between the apolar solutes whereas hydrophobic hydration deals with the change in water structure in presence of non polar solute [4]. When the highly dynamic hydrogen bonds get disrupted, hydrophobic interactions are originated [5]. ...
... The PMF curve shows a characteristic shape with deep minima at about 0.49 nm, 0.50 nm and 0.53 nm for water, acetonitrile and methanol respectively.The comparison of the obtained results for propane dimer in water with the previous works shows good agreement. In the reference[5] the position of contact minima and solvent separated minima are 0.49 nm and 0.82 nm respectively. Our result for position of contact minima (0.49 nm) corresponds with the reference and the result for position of second minima (0.84 nm) shows a discrepancy of 2.4%[8]. ...
Molecular Dynamics (MD) simulations of propane dimer in different solvents (water, acetonitrile and methanol) were performed by using CHARMM platform for modeling the solute and solvents. A series of Umbrella sampling MD simulations were carried out in each solvent separately and potential of mean force (PMFs) were calculated by using Weighted Histogram Analysis Method. Results show that two minima (contact minima and solvent separated minima) characterize the PMF of propane dimer in all three solvent environments. The contact minima are deeper and less sensitive to solvent environment for its position. However, significant effect in the position of second minima, solvent separated minima, was observed. Our study reveals that the interaction between propane dimer is softer in methanol and acetonitrile than in water. BIBECHANA 17 (2020) 1-12
... This factor is related to the decrease in the thermal-random motion of the water molecules, which are immediately joined to the layer of the oily phase. Such an entropic factor is the main reason for destabilization in heterodisperse systems (emulsions), because this leads to a series of dynamic events that end with the break of the system (phase separation), creating a tiny contact area known as an interface flat [33,34]. Therefore, in this assay, polysorbate 80 and sorbitan 80 surfactants were selected due to several reasons. ...
... This factor is related to the decrease in the thermalrandom motion of the water molecules, which are immediately joined to the layer of the oily phase. Such an entropic factor is the main reason for destabilization in heterodisperse systems (emulsions), because this leads to a series of dynamic events that end with the break of the system (phase separation), creating a tiny contact area known as an interface flat [33,34]. Therefore, in this assay, polysorbate 80 and sorbitan 80 surfactants were selected due to several reasons. ...
Sacha inchi oil is a premier raw material with highly nutritional and functional features for the foodstuff, pharmaceutical, beauty, and personal care industries. One of the most important facts about this oil is the huge chemical content of unsaturated and polyunsaturated fatty acids. However, the current available information on the characterization of the triglyceride composition and the advance physicochemical parameters relevant to emulsion development is limited. Therefore, this research focused on providing a detailed description of the lipid composition using high-resolution tandem mass spectrometry and thorough physicochemical characterization to find the value of the required hydrophilic–lipophilic balance (HLB). For this, a study in the interfacial tension was evaluated, followed by the assessment of different parameters such as creaming index, droplet size, viscosity, zeta potential, pH, and electrical conductivity for a series emulsified at thermal stress condition. The results show that fatty acids are arranged into glycerolipids and the required HLB to achieve the maximum physical stability is around 8.
... Most hydrocarbons have a negligible mixing enthalpy and negative, high-magnitude mixing entropy in water. This gives rise to the hydrophobic effect [17]. The polar H 2 O molecules and nonpolar hydrocarbons arrange themselves in a specific way at the interface, leading to a reduction in microstates per macrostate, i.e., less entropy at the interface. ...
This paper introduces a novel methodology for the mathematical modelling of first and second order phase transformations. It will be shown that this methodology can be related to certain limiting cases of the Cahn-Hilliard equation, specifically the cases of having (i) a convex molar free energy function and (ii) a convex molar free energy function with no regularization. The latter case is commonly regarded as unstable; however, by modifying the variational approach and solving for rate-dependent variables, we obtain a stabilized method capable of handling the missing regularization. While the specific numerical method used to solve the equations (a mixed finite element approach) has been previously employed in related contexts (e.g., to stabilize solutions of the Laplace equation), its application to diffusion and diffusional phase transformations is novel. We prove the thermodynamic consistency of the derived method and discuss several use cases. Our work contributes to the development of new mathematical tools for modeling complex phase transformations in materials science.
... Typical explanations are based on the relative strength of the interaction between different types of particles, failing to recognize that both phenomena are entropically driven given that the enthalpy change for these processes is either positive (NaCl dissolution) or close to zero (oil−water mixing). 37 This bias toward force/energy-based explanations is also present in typical rationales built by instructors and presented in educational materials 38 to explain the relative strength of organic acids and bases in water. In these cases, the relative energetic stability of the chemical entities is frequently used to justify outcomes, ignoring the rather important entropic effects due to the solvation of charged species. ...
... At the initial time point, as depicted in Figure 4.24 (a), representing the condition before activating the ultrasound, a thin film of oil is visible on the surface of the water. The oil and water do not naturally mix due to their differing polarities and densities, causing them to separate into distinct layers when combined [164]. ...
This dissertation examined the effects of ultrasound in different stages of a Wastewater Treatment Plant (WWTP), focusing on adsorption and oxidation processes. Additionally, it provided guidance for the proper design of an ultrasound-assisted equipment aimed at water treatment.
Initially, the physical effects of ultrasound treatment on water were explored. The initial understanding of these phenomena guided the research in two distinct directions. On one hand, the feasibility of combining ultrasound treatment with existing adsorption mechanisms was investigated. On the other hand, the potential of this technology in isolation for wastewater treatment was examined.
In the context of wastewater treatment, sensors were developed to monitor acoustic cavitation within the ultrasound equipment. After validating the sizing of this equipment, a study was conducted at a WWTP to evaluate the effectiveness of ultrasound treatment in water contaminated with various pollutants and
organisms. The application of ultrasound proved impactful in the initial moments. When applied to ultra-filtered water, ultrasound treatment (Is=20.7 ± 1.6 W·cm−2) in the first 18 seconds resulted in a 2.7-fold increase in ORP and a 2.29-fold reduction in pH. The combination of ultrasound treatment with the organic compound ”Nutrimais da Lipor” in adsorption resulted in a Cu removal rate of 82%, surpassing conventional mechanical action by 4.3 times. The removal of CIP was accelerated, reaching the maximum adsorption capacity (70%) in 1 minute, being 1.75 times more effective than the mechanical approach. With the Kaolin adsorbent, both
methods showed comparable results after 1 minute. Regarding the treatment of contaminated water at the WWTP, the developed sensors for monitoring
acoustic cavitation identified cavitation thresholds and transition zones, confirming the geometric dimensions of the ultrasound chamber.
Applying ultrasound treatment with different powers (200 W, 400 W, and 800 W) showed a significant variation in physicochemical parameters in the first 5 minutes, followed by stabilization and return to initial values. COD decreased in the first 2 to 5 minutes, then returned to initial values. These results highlight the potential of ultrasound treatment, especially in the initial stages of application, for accelerating processes and the possibility of integration with other methods.
Atribuição CC BY https://creativecommons.org/licenses/by/4.0/
... RBCO has black brown color while light distillate consists of two phases, which are oil phase (A) and aqueous phase (B) as captured in Fig. 7. The formation of two phases is attributed to the principle of "like dissolves like" where the non-polar oil phase cannot dissolve in the polar aqueous phase (Silverstein 1998). There is no significant difference in the physical appearance of light distillate under temperature and pressure variations. ...
Sustainable chemical production through biomass pyrolysis is attractive. This is necessary to suppress massive dependence on fossil resources. Nevertheless, the liquid product as raw bio-crude oil (RBCO) from biomass pyrolysis still contains high water content. In this study, batch vacuum distillation of RBCO from empty fruit bunches (EFB) pyrolysis was performed at 80 95 °C and 30 45 kPa to produce light distillate. The highest yield of light distillate is acquired at 69.73–88.27% under 95 °C and 30 kPa. The functional groups in RBCO and light distillate indicate the presence of water (O–H bond), acetic acid (C = O bond), and phenol (C = C–C aromatic ring and O–H bond). This is also proven by the results from Karl-Fischer of RBCO that water contained at 66.77% whereas GC–MS of RBCO show the concentrations of acetic acid is 16.02% and phenol is 26.53%. Physically, the light distillate had a light brown color and smoky odor, with density range of 0.96–0.99 g/ml and viscosity range of 0.60–0.93 cP. According to this study, light distillate has water content of 70.57–98.81%. During vacuum distillation, acetic acid and phenol, as the major chemicals contained in RBCO, are also dissolved in the aqueous phase with the highest concentrations of 0.28% and 0.09%, respectively. Looking at its chemical components, this light distillate has the potential for food preservatives or agricultural biopesticides.
... Inspirationally, this can be considered to resemble how disorder can actually create order in nature. One such example is when non-polar molecules become spontaneously sorted from water by the laws of entropy, as the number of microstates manifesting the fixed ice cages required for the solvation are severely overrun by the microstates representing the free water molecules (Frank and Evans 1945;Silverstein 1998). Similarly, problematic factors can emerge spontaneously, without conscious decisions or acts to realize them, when design choices are made and concepts embodied, due to the unavoidable number of microstates the problematic macrostates cover. ...
... The role of the hydrophobic bases can be tuned by facilitating hydrophobic interactions 31 as induced by the entropy effect caused by nonpolar solutes destroying hydrogen bonds between water molecules. 32,33 Techniques such as rolling circle amplification (an isothermal amplification process) can efficiently produce a high quantity of long ssDNA (lssDNA), where the byproduct counterions may largely control the extent of hydrophobic interactions. Certain concentrations of counterions can screen the surface charge of lssDNA, whereas the aromatic structures of lssDNA are intrinsically hydrophobic. ...
Controlling the DNA translocation speed is critical in nanopore sequencing, but remains rather challenging in practice, as attributable to a complex coupling between nanoscale fluidics and electrically mediated migration of DNA in a dynamically evolving manner. One important factor influencing the translocation speed is the DNA-liquid slippage stemming from the hydrophobic nature of the oligonucleotide, an aspect that has been widely ignored in the reported literature. In an effort to circumvent this conceptual deficit, here we first develop an analytical model to bring out the slip-mediated coupling between the electroosmosis and DNA-electrophoresis in a solid-state nanopore at low surface charge limits, ignoring the end effects. Subsequently, we compare these results with the numerical simulation data on electrokinetically modulated DNA translocation in such a nanopore, albeit of finite length with due accommodation of the end effects, connecting two end reservoirs by deploying a fully coupled Poisson-Nernst-Plank-Stokes flow model. Both the numerical and analytical results indicate that the DNA translocation speed is a linearly increasing function of the slip length, with more than four-fold increase being observed for a slip length as minimal as 0.5 nm as compared to the no-slip scenario. Considering specific strategies on demand for arresting high translocation speeds for accurate DNA sequencing, the above results establish a theoretical proposition for the same, premised on an analytical expression of the DNA-hydrophobicity modulated enhancement in the translocation speed for designing a nanopore-based sequencing platform─a paradigm that remained to be underemphasized thus far.
... The hydrophobic interaction is entropy dependent. The force behind hydrophobic interaction is induced from the breaking of hydrogen bonds [51]. We will try to analyze our experiment with the thermodynamic factors which give rise to the hydrophobic effect. ...
Cold shock proteins (CSPs) are small, acidic proteins which contain a conserved nucleic acid-binding domain. These perform mRNA translation acting as “RNA chaperones” when triggered by low temperatures initiating their cold shock response. CSP- RNA interactions have been predominantly studied. Our focus will be CSP-DNA interaction examination, to analyse the diverse interaction patterns such as electrostatic, hydrogen and hydrophobic bonding in both thermophilic and mesophilic bacteria. The differences in the molecular mechanism of these contrasting bacterial proteins are studied. Computational techniques such as modelling, energy refinement, simulation and docking were operated to obtain data for comparative analysis. The thermostability factors which stabilise a thermophilic bacterium and their effect on their molecular regulation is investigated. Conformational deviation, atomic residual fluctuations, binding affinity, Electrostatic energy and Solvent Accessibility energy were determined during stimulation along with their conformational study. The study revealed that mesophilic bacteria E. coli CSP have higher binding affinity to DNA than thermophilic G. stearothermophilus. This was further evident by low conformation deviation and atomic fluctuations during simulation.
Graphical Abstract
... Hal ini dikarenakan protein memiliki sifat higroskopis sehingga pergerakan masa air terjadi dari udara di ruang penyimpanan kepada benih (Tatipati, 2007). Meski benih kelapa sawit mengandung protein, namun komponen tersebut berada dalam proporsi yang kecil, 7,5-9%, sedangkan komponen terbesarnya adalah lemak sebesar 47-52% (Hartley dalam Corley dan Tinker, 2016) dimana lemak bersifat hydrophobic (Silverstein, 1998). ...
Faktor yang mempengaruhi penurunan vigor benih selama penyimpanan adalah suhu dan kelembapan ruang penyimpanan serta kemasan yang digunakan. Penelitian ini bertujuan mendapatkan informasi pengaruh kemasan terhadap kemampuannya dalam mempertahankan kadar air (KA) dan daya hantar listrik (DHL) benih kelapa sawit pada ruang penyimpanan ber-AC. Penelitian dilaksanakan dengan rancangan acak lengkap faktor tunggal yaitu kemasan simpan dengan tiga taraf: plastik polypropylene (PP) satu rangkap (M1), PP dua rangkap (M2), dan plastik vakum (M3). Hasil percobaan memperlihatkan bahwa penyimpanan di ruang AC menyebabkan penurunan KA benih dengan laju yang berbeda antar-taraf dimana terjadi penguapan air dari total air yang ada di dalam benih sebesar 11,47% pada M3, lebih tinggi dibanding M1 (8,13%) dan M2 (6,18%). Meski ketiga taraf memperlihatkan penurunan nilai KA benih, namun kisaran KA pada akhir percobaan (13,8%) masih berada di atas ambang yang diijinkan (10-12%) untuk penyimpanan benih kelapa sawit, sebagaimana nilai DHL pada akhir percobaan (2,69 – 3,04 µS.cm-1.g-1). Untuk penyimpanan jangka pendek selama 104 hari, kedua parameter memperlihatkan korelasi positif dengan nilai koefisien korelasi sebesar 0,77.
... These phenomena show that PPC, similar polarity to the electrolyte, can enhance the wettability of CP substrate, benefitting from the "like dissolves like" of PPC with PC in electrolyte. [25] By evaluating the wettability of the separator, it was found that the CP@PPC separator achieved more adequate and rapid electrolyte uptake and ion penetration compared to the CP (Table S1 and Figure S3, Supporting Information). ...
Sodium‐ion batteries (SIBs) have great potential for large‐scale energy storage. Cellulose is an attractive material for sustainable separators, but some key issues still exist affecting its application. Herein, a cellulose‐based composite separator (CP@PPC) was prepared by immersion curing of cellulose‐based separators (CP) with poly(propylene carbonate) (PPC). With the assistance of PPC, the CP@PPC separator is able to operate the cell stably at high voltages (up to 4.95 V). The “pore‐hopping” ion transport mechanism in CP@PPC opens up extra Na⁺ migration paths, resulting in a high Na⁺ transference number (0.613). The separator can also tolerate folding, bending and extreme temperature under certain circumstances. Full cells with CP@PPC reveal one‐up capacity retention (96.97 %) at 2C after 500 cycles compared to cells with CP. The mechanism highlights the merits of electrolyte analogs in separator modification, making a rational design for durable devices in advanced energy storage systems.
... The formation of the particles is proceeded based on the self-assembly of the constituents induced by robust hydrophobic interactions between fluorine groups of the macromolecules and hydrous in the aqueous solution (Xiao et al., 2013). It is known that non-polar solutes with hydrophobic interactions can disrupt hydrogen bonds between water molecules (Silverstein, 1998;Xiao et al., 2013). Therefore, the P(VDF-TrFE) chain tends to aggregate in the form of nanoparticles because it is incapable of hydrogen bonds with water molecules. ...
Theranostic liposomes have recently found a broad range of applications in nanomedicine due to stability, the high solubility of biomacromolecules, bioavailability, efficacy, and low adverse effects. However, the limitations of liposomes concerning the short systemic circulation in the body, limited controllability of the release rate, and the inability of in vivo imaging remain challenging. Herein, the development of novel hybrid ultrasound-activated piezoelectric nanoparticles based on a hybrid liposome nanocarrier composed of poly(vinylidene fluoride‐trifluoroethylene), graphene quantum dots (GQDs), and Silibinin (a hydrophobic drug) is presented. The hybrid nanoparticles are an acoustically sensitive drug delivery platform that releases the biomacromolecules in a specific tissue area (through surface labeling with PD-1 antibody) in a non-invasive and controlled manner. We show that the developed hybrid nanoparticles (with an average outer diameter of ∼230±20 nm) enable piezoelectric-stimulated drug delivery combined with simultaneous fluorescent imaging of cancer cells in vivo. Significant enhancement (>80% up to 240 h) and tunable drug release from the nanocarrier through enhanced diffusion from the liposome membrane are demonstrated. Cytotoxicity assays using MCF-7, 4T1, and NIH3T3 cell lines exhibit no confrontational influence of nanoparticles on cell viability up to 125 µg/ml. The PD-1 antibody on the surface of the hybrid nanocarrier allows for selective delivery to breast cancer tumors and low biodistribution to other tissues. Our results affirm that the developed ultrasound-activated piezoelectric nanoparticles have great potential as multifunctional platforms with sustainable release profiles for the delivery of hydrophobic drugs to breast cancer, especially when the ability for adequate labeling and cell monitoring is valued.
... It is a familiar idea that oil and water don't mix [Silverstein (1998)]. Since oils and other small molecules are being extracted from coffee beans, one might probably think that there should exist two separate phases-water and oil, probably floating on top. ...
Droplet evaporation is omnipresent in nature, science and in numerous advanced technologies. The evaporation of colloidal dispersions is an elegant and straightforward
route to achieve controlled self-assembly of particles on a solid surface. In particular,
the evaporation of particle laden drops placed on solid substrates has received considerable attention for more than two decades. Such particle filled drops upon complete evaporation of the solvent leave behind a residue, commonly called particulate deposit pattern. In these patterns, typically, more particles accumulate at the edge compared to the interior, a feature observed when coffee drops evaporate. Consequently, such evaporative patterns are called coffee-stains. In this contribution, the focus is on the
evaporation of highly dilute suspension drops containing particles of larger diameters
ranging from 3 microns to 10 microns drying on solid substrates. This helps in the investigation
of the combined role of gravity-driven settling of particles and capillary flow-driven
particle transport on pattern formation in drying drops. In the highly dilute concentration
limit, the evaporative patterns are found to show a transition, from a monolayer
deposit that consists of a single layer of particles, to a multi-layer deposit as a function
of particle diameter and initial concentration of particles in the drying drop. Moreover,
the spatial distribution of particles as well as the ordering of particles in the deposit
patterns are found to be particle size dependent. It is also seen that the order-disorder
transition, a feature associated with the organization of particles at the edge of the deposit, observed typically at moderate particle concentrations, disappears at the highly
dilute concentrations considered here. The evaporation of drops containing particles of
10 microns diameter, where the effect of gravity on the particle becomes significant, leads
to uniform deposition of particles, i.e, suppression of the coffee-stain effect and to the formation of two-dimensional percolating networks.
... Ferrofluid robots have promising applications in targeted therapies due to their fluidic properties. Studies have shown that ferrofluid robots have good self-assembling properties in liquid environments where they are immiscible [19], [20]. Its high deformability allows it to pass through narrow channels and over obstacles [21]. ...
Magnetic-controlled micro-robots have promising applications in disease therapy due to their high targetability and drug utilization. Due to their unique deformable and divisible properties, ferrofluid robots have gained much attention in microchemical reaction chips and micromanipulation. This letter proposes a biocompatible ferrofluid robot and validates its potential to achieve targeted drug delivery and tumor cell killing. This biocompatible ferrofluidic robot contains 10 nm oleic acid-coated ferric tetroxide particles and vegetable oil and has good magnetic responsiveness, deformability, and photothermal properties, and can move in liquid environments such as blood. It can achieve motion with an error of less than 0.4 mm under closed-loop control and obstacle overturning and passage through narrow channels less than twice its diameter. In addition, the biocompatible ferrofluid robot can kill tumor cells in the target area due to the photothermal properties of the magnetic particles, and experimental results show that the tumor cell death rate can reach 95%. These capabilities give the biocompatible ferrofluid robot a significant advantage in getting the target location for cancer treatment through the vascular environment.
... From a structural adaptation perspective, hydrophilic NH 1/2 groups can even reorientate to enrich at the water interface, replacing the originally surface-dominant hydrophobic C x H y or C x F z groups. 27,28 These structural changes further enhance protonation (increasing q 2 + ). With the monoamine, PFOTS-APTES, positive drop/ negative surface charging is never observed (i.e., net q 2 + > net q 1 − ). ...
When a water drop slides over a hydrophobic surface, it usually acquires a positive charge and deposits the negative countercharge on the surface. Although the electrification of solid surfaces induced after contact with a liquid is intensively studied, the actual mechanisms of charge separation, so-termed slide electrification, are still unclear. Here, slide electrification is studied by measuring the charge of a series of water drops sliding down inclined glass plates. The glass was coated with hydrophobic (hydrocarbon/fluorocarbon) and amine-terminated silanes. On hydrophobic surfaces, drops charge positively while the surfaces charge negatively. Hydrophobic surfaces coated with a mono-amine (3-aminopropyltriethyoxysilane) lead to negatively charged drops and positively charged surfaces. When coated with a multiamine (N-(3-trimethoxysilylpropyl)diethylenetriamine), a gradual transition from positively to negatively charged drops is observed. We attribute this tunable drop charging to surface-directed ion transfer. Some of the protons accepted by the amine-functionalized surfaces (-NH2 with H+ acceptor) remain on the surface even after drop departure. These findings demonstrate the facile tunability of surface-controlled slide electrification.
... The low solubility is because the attraction force between water and oil molecules is weak and not able to overcome the very strong hydrogen bonding that water has with itself. 1,2 In oil, water can exist as dissolved, emulsified, and free water (see Figure 1.1). 3 Dissolved water is characterized by individual water molecules, surrounded by oil molecules. Lubricant oil containing dissolved water appears bright and clear and typically causes less damage to engine parts than other forms of water in oil. ...
Karl Fischer Titration (KFT) is the “gold standard” method for measuring the amount of water in oils. KFT is a laborious and time-consuming method that requires expensive and hazardous chemicals which has provided the impetus to develop alternative methods. In this thesis, we investigated three approaches for determining water content in oils that are based on the use of infrared spectroscopy. In the first approach, we developed a simple method for measuring water concentrations from 1 to 5000 ppm in various types of oil that uses no hazardous, and expensive, chemical reagents or matrix specific calibrations. This approach involves capturing the water from the oil on an infrared transparent membrane and then recording an IR spectrum in transmission mode through the membrane. The second approach involves adding CaO powder to an oil sample and measuring the amount of Ca(OH)2 produced by the reaction of CaO with water. The Ca(OH)2 particles was collected on an infrared transparent membrane for analysis by infrared spectroscopy. No calibration is required and the amount of water is determined from measuring the intensity of the OH stretching mode of Ca(OH)2 at 3645 cm-1. The third approach is based on adding CuSO4 to the oil and forms copper sulfate monohydrate after reacting with water. The CuSO4·H2O particles are collected by passing a known volume of oil through the membrane and measuring the intensity of the bending mode of the water band at 1743 cm-1. All three methods achieved high accuracy and precision when compared to KFT over a linear range of 1 ppm to 10000 ppm. These were achieved by overcoming problems from light scattering by the water droplets, as well as the distortions in the water bands due to interactions of the water with the oil that occur when measuring water levels using transmission in a fixed pathlength liquid cell, as described in the ASTM standard practice E2412 method. Our recommendation and preference is the CaO method because it does not require a cooling stage, that is used in the membrane method, and can be used with a wider range of oils than what is possible with CuSO4·H2O.
... There was no chemical change after the mixture of CS and β-GP, and the gel-sol transition was achieved by the physical action between the two molecules and water molecules. At high temperature, the molding ability of the spatial cage structure of molecular chains was significantly better than that of the F127 snowflake structure [36,37,43]. ...
One of the biggest hinders in tissue engineering over the last decades was the complexity of the prevascularized channels of the engineered scaffold, which was still lower than that of human tissues. Another relative trouble was lacking precision molding capability, which restricted the clinical applications of the huge engineered scaffold. In this study, a promising approach was proposed to prepare hydrogel scaffold with prevascularized channels by liquid bath printing, which chitosan/β-sodium glycerophosphate (CS/β-GP) severed as the ink hydrogel, and gelation/nanoscale bacterial cellulose (Gel/BC) acted as the supporting hydrogel. Here, the ink hydrogel was printed by a versatile nozzle and embedded in the supporting hydrogel. Ink hydrogel transformed into liquid effluent at low temperature after cross-linking of gelatin by microbial transglutaminase (mTG). No residual template was seen on the channel surface after template removal. This preparation had a high degree of freedom in the geometry of the channel, which was demonstrated by making various prevascularized channels including circular, branched, and tree-shaped networks. The molding accuracy of the channel was detected by studying the roundness of the cross-section of the molded hollow channel, and the effect of the mechanical properties by adding BC to supporting hydrogel was analyzed. Human umbilical vein endothelial cells (HUVECs) were injected into the aforementioned channels and formed confluent and homogeneous distribution on the surface of channels. Altogether, these results showed that this approach can construct hydrogel scaffold with complex and accurate molding prevascularized channels, and had great potential to resolve urgent vascularization issue of bulk tissue-engineering scaffold.
... 56 It plays a role in the self-assembly process as the SASA of the hydrophobic tails keeps decreasing ( Figure S10), which regenerates the dynamic water networks and contributes favorably to the increase of the entropy of the system. 57 However, there are also opposite entropic contributions, such as that from the translational, rotational, and conformational movements of lipids, which are largely suppressed in the bilayer state. The overall effect is that the entropy term increases unfavorably as the self-assembly proceeds ( Figure 2b). ...
Self-assembly is ubiquitous in the realm of biology and has become an elegant bottom-up approach to fabricate new materials. Although molecular dynamics (MD) simulations can complement experiments by providing the missing atomic details, it still remains a grand challenge to reveal the thermodynamic and kinetic information on a self-assembly system. In this work, we demonstrate for the first time that the Markov state model analysis can be used to delineate the variation of free energy during the self-assembly process of a typical amphiphilic lipid dipalmitoyl-phosphatidylcholine (DPPC). Free energy profiles against the solvent-accessible surface area and the root-mean-square deviation have been derived from extensive MD results of more than five hundred trajectories, which identified a metastable crossing-cylinder (CC) state and a transition state of the distorted bilayer with a free energy barrier of ∼0.02 kJ mol-1 per DPPC lipid, clarifying a long-standing speculation for 20 years that there exists a free energy barrier during lipid self-assembly. Our simulations also unearth two mesophase structures at the early stage of self-assembly, discovering two assembling pathways to the CC state that have never been reported before. Further thermodynamic analysis derives the contributions from the enthalpy and the entropy terms to the free energy, demonstrating the critical role played by the enthalpy-entropy compensation. Our strategy opens the door to quantitatively understand the self-assembly processes in general and provides new opportunities for identifying common thermodynamic and kinetic patterns in different self-assembly systems and inspiring new ideas for experiments. It may also contribute to the refinement of force field parameters of various self-assembly systems.
... However, if an oil particle is presented along with the LCFAs in the media, the saponified LCFA can facilitate the dissolving/dispersion of this oil particle in water. To be specific, the hydrophobic tails of saponified LCFA are directed to the oily contaminant, while the hydrophilic heads are directed to outer layer; this leads to dispersed micelles formation ( Shah et al., 2016 ;Silverstein, 1998 ). ...
The inhibition of the anaerobic digestion (AD) process, caused by long chain fatty acids (LCFAs), has been considered as an important issue in the wastewater treatment sector. Proper understanding of mechanisms behind the inhibition is a must for further improvements of the AD process in the presence of LCFAs. Through analyzing recent literature, this review extensively describes the mechanism of LCFAs degradation, during AD. Further, a particular focus was directed to the key parameters which could affect such process. Besides, this review highlights the recent research efforts in mitigating LCFAs-caused inhibition, through the addition of commonly used additives such as cations and natural adsorbents. Specifically, additives such as bentonite, cation-based adsorbents, as well as zeolite and other natural adsorbents for alleviating the LCFAs-induced inhibition are discussed in detail. Further, panoramic evaluations for characteristics, various mechanisms of reaction, merits, limits, recommended doses, and preferred conditions for each of the different additives are provided. Moreover, the potential for increasing the methane production via pretreatment using those additives are discussed. Finally, we provide future horizons for the alternative materials that can be utilized, more efficiently, for both mitigating LCFAs-based inhibition and boosting methane potential in the subsequent digestion of LCFA-related wastes.
... Essentially, the source of the hydrophobic effect is the entropy effect caused by nonpolar solutes destroying hydrogen bonds between water molecules. [28,29] In biophysics, hydrophobic interactions play an essential role in the 3D structure of proteins. [30] For a globular protein, its surface is usually surrounded by a layer of hydrophilic residues in aqueous solution, and residues with hydrophobic side chains are usually inside the protein. ...
The comprehensive understanding and proper use of supramolecular interactions have become critical for the development of functional materials, and so is the biomedical application of nucleic acids (NAs). Relatively rare attention has been paid to hydrophobic interaction compared with hydrogen bonding and electrostatic interaction of NAs. However, hydrophobic interaction shows some unique properties, such as high tunability for application interest, minimal effect on NA functionality, and sensitivity to external stimuli. Therefore, the widespread use of hydrophobic interaction has promoted the evolution of NA‐based biomaterials in higher‐order self‐assembly, drug/gene‐delivery systems, and stimuli‐responsive systems. Herein, the recent progress of NA‐based biomaterials whose fabrications or properties are highly determined by hydrophobic interactions is summarized. 1) The hydrophobic interaction of NA itself comes from the accumulation of base‐stacking forces, by which the NAs with certain base compositions and chain lengths show properties similar to thermal‐responsive polymers. 2) In conjugation with hydrophobic molecules, NA amphiphiles show interesting self‐assembly structures with unique properties in many new biosensing and therapeutic strategies. 3) The working‐mechanisms of some NA‐based complex materials are also dependent on hydrophobic interactions. Moreover, in recent attempts, NA amphiphiles have been applied in organizing macroscopic self‐assembly of DNA origami and controlling the cell–cell interactions.
... This will result in less attachment of the cells to the surface of the medium and thus enhancement in cell transport (Figure 5c). Such a mechanism is in accordance with previous description of the essence of hydrophobic interaction that it is the sole consequence of the hydrogen-bonding energy of cohesion of the water molecules surrounding the apolar moieties (van Oss, 1995), or it is mostly an entropic effect originating from the disruption of highly dynamic hydrogen-bonding between molecules of liquid water by the nonpolar solute (Silverstein, 1998). Hydrogen bonding can be viewed as a form of more general electron-donor/electron-accepter interaction, namely, Lewis acid-base interaction (van Oss, 1991). ...
Transport of P. aeruginosa ATCC 9027 in quartz sands mediated by low‐concentration surfactants of sodium dodecyl benzene sulfonate (SDBS) or Triton X‐100 was investigated with column experiments. P. aeruginosa ATCC 9027 was cultured with glucose and hexadecane to produce cells with different initial cell surface hydrophobicity (CSH). Transport behavior of cells was characterized by breakthrough curves (BTCs) and deposition rate coefficients (kd) values were estimated by fitting the BTCs using colloid transport models. Relations between kd and CSH represented by bacterial‐adsorption‐to‐hydrocarbon fraction (BATH fraction) and between kd and cell surface charge represented by zeta potential were analyzed to quantitatively describe the effect of surfactants on cell transport. Results showed that at low concentrations the ionic SDBS increased cell surface charge while the nonionic Triton X‐100 had no effect, while both of them caused significant differentiation of CSH. The kinetic attachment‐detachment model with blocking was the best among the five models tested to fit BTCs and low‐concentration SDBS and Triton X‐100 caused remarkable change of kd. A good linear relation between kd and cell BATH fraction was observed (R² = 0.82), whereas the linearity between kd and total zeta potential of cell and sand was poor (R² = 0.11). The data reconstructed from our previous studies showed that the linearity between kd and cell BATH fraction also presented in sands and glass beads for low‐concentration rhamnolipid biosurfactant. In all, these results showed that CSH plays a critical role in cell transport in porous media and changing CSH is a common mechanism for low‐concentration surfactants to mediate the transport, which implies the potential of using low‐concentration surfactants to regulate bacterial transport for bioaugmentation.
... Even though this type of interaction causes the apparent repulsion between water and hydrocarbon molecules, it cannot be directly related to the formation of physical bonds. The hydrophobic effect, which is one of the major driving forces for the formation of lipid bilayers and micelles, results from the contributions of both van der Waals forces between hydrocarbon compounds and hydrogen bonding between water molecules [34,35]. Therefore, the term "hydrophobic effect" should be preferred to "hydrophobic bonding". ...
Objective:Molotov cocktails are a classic homemade weapon used over the past 80 years; also known as gasoline bombs. However, there is not enough research in the literature. Molotov cocktail is classified as a mildly explosive substance. But a Molotov cocktail is not an explosive. This is a handmade lighter. It is used to set fire to targets in terrorist attacks. Methods:In our study, classic homemade Molotov cocktails were used. Oil, diluent, sugar, cologne, epoxy resin, paraffin, egg white, liquid and solid detergent, bleach, wood glue were added to the mixture. Parameters such as burning temperature, burning time, glass and nail spreading diameter, and residues of the Molotov cocktail were investigated. The prepared molotov cocktails were broken on 5 different floors, and the effect of changing the floor on the parameters was investigated. Results:In our study, 51 (59.3%) of 86 molotov cocktails were broken. Most of the destruction occurred in the wall. According to the results we obtained, a relationship was found between the content of the Molotov cocktail, the burning temperature and the time. It was found that the damage was increased with the addition of substances to the mixture. Conclusion: In addition, in our study, it was noticed that the Molotov cocktail did not explode by itself and did not cause damage to the environment by throwing nails.
Polymers with upper critical solution temperature (UCST) can find a promising application in biocatalysis by immobilized enzymes, in that UCST-type polymer-immobilized enzymes use lower temperatures for biocatalyst separation than for...
At low surfactant concentrations often non-linear sorption processes are observed when more complex natural adsorbents like sediment or soil are involved. This sorption process is often explained by a Dual-Model (DM) model, which assumes sorption to the organic matter fraction to be based on a combined electrostatic and hydrophobic sorption interaction term. An Independent-Mode (IM) model, however, could treat surfactant sorption as two independent sorption processes to which the hydrophobic and electrostatic features of the surfactant molecule contribute differently. For both models the overall true partition coefficient, Kptotal, and its corresponding total standard free enthalpy of adsorption, ΔsG0total, are derived. We tested the outcome of both models against multiple published experimental sorption data sets by, (i) varying the organic carbon fraction, (ii) constructing sorption and partition isotherms over different concentration ranges, (iii) removing the organic carbon fraction, (iv) applying different types of mixtures of surfactants, and (v) explaining sorption hysteresis in desorption studies based on either continuous and successive washing steps. It turned out that only the Independent-Mode (IM) only was able to explain the reported sorption phenomena. We also show that when one interaction is dominating, e.g. hydrophobic over electrostatic, the ΔsG0total of the IM model can be approximated by the sum of the different ΔsG0 values, the ΔsG0total of the DM model. The true partition coefficient, Kp(Cw) (L/kg) = dCs(mmol/kg)/dCw(mmol/L), is turning each sorption isotherm into a partition isotherm that provides the Kp values required in environmental risk assessment models.
The demand for green and non-toxic hair dyes has continued to grow in recent years as the majority of consumers preferred natural and healthy products. There are a series of...
Ferrofluidic robots with excellent deformability and controllability have been intensively studied recently. However, most of these studies are in vitro and the use of ferrofluids for in vivo medicinal applications remains a big challenge. The application of ferrofluidic robots to the body requires the solution of many key problems. In this study, biocompatibility, controllability, and tumor‐killing efficacy are considered when creating a ferrofluid‐based millirobot for in vivo tumor‐targeted therapy. For biocompatibility problems, corn oil is used specifically for the ferrofluid robot. In addition, a control system is built that enables a 3D magnetic drive to be implemented in complex biological media. Using the photothermal conversion property of 1064 nm, the ferrofluid robot can kill tumor cells in vitro; inhibit tumor volume, destroy the tumor interstitium, increase tumor cell apoptosis, and inhibit tumor cell proliferation in vivo. This study provides a reference for ferrofluid‐based millirobots to achieve targeted therapies in vivo.
In the last decades, cross-coupling approaches have been widely used to generate structural diversity efficiently. Among various transition-metals, palladium has remained the most understood metal to efficiently catalyze cross-couplings. The introduction of sustainability parameters, such as atom-economy, process mass intensity (PMI), or E-factor highlighted the fundamental inefficiencies associated with the traditional practices in organic synthesis. Critical analysis in the context of these factors identified organic solvents as the major culprit. In this scenario, employing water as a bulk reaction medium for cross-couplings has emerged as an attractive alternative. Fine-tuning the solvation features of water by adding non-ionic surfactant provides an exciting opportunity to practice sustainable organic synthesis. This approach has gained substantial attention in the last ten years and established a basic framework for practicing organic chemistry under aqueous conditions, ultimately reducing the reliance on toxic organic solvents. In this review, along with the future directions and challenges, recent advances in the field of micellar catalysis applied to palladium mediated cross-couplings will be discussed.
While many good textbooks are available on Protein Structure, Molecular Simulations, Thermodynamics and Bioinformatics methods in general, there is no good introductory level book for the field of Structural Bioinformatics. This book aims to give an introduction into Structural Bioinformatics, which is where the previous topics meet to explore three dimensional protein structures through computational analysis. We provide an overview of existing computational techniques, to validate, simulate, predict and analyse protein structures. More importantly, it will aim to provide practical knowledge about how and when to use such techniques. We will consider proteins from three major vantage points: Protein structure quantification, Protein structure prediction, and Protein simulation & dynamics. In the previous chapter, "Introduction to Protein Folding", we introduced the concept of free energy and the protein folding landscape. Here, we provide a deeper, more formal underpinning of free energy in terms of the entropy and enthalpy; to this end, we will first need to better define the meaning of equilibrium, entropy and enthalpy. When we understand these concepts, we will come back for a more quantitative explanation of protein folding and dynamics. We will discuss the influence of temperature on the free energy landscape, and the difference between microstates and macrostates.
Completely revised and updated, the 2nd edition of The Handbook of Medicinal Chemistry draws together contributions from authoritative practitioners to provide a comprehensive overview of the field as well as insight into the latest trends and research. An ideal companion for students in medicinal chemistry, drug discovery and drug development, while also communicating core principles, the book places the discipline within the context of the burgeoning platform of new modalities now available to drug discovery. The book also highlights the role chemistry has to play in wider target validation and translational technologies.
This is a carefully curated compilation of writing from global experts using their broad experience of medicinal chemistry, project leadership and drug discovery and development from an industry, academic and charity perspective to provide unparalleled insight into the field.
Sodium‐ion batteries (SIBs) have great potential for large‐scale energy storage. Cellulose is an attractive material for sustainable separators, but still exists some key issues affecting its application. Herein, cellulose‐based composite separator (CP@PPC) was prepared by immersion curing of cellulose‐based separators (CP) with polypropylene carbonate (PPC). With the assistance of PPC, CP@PPC separator is able to operate the cell stably at high voltages (up to 4.95 V). The "pore‐hopping" ion transport mechanism in CP@PPC opens up extra Na+ migration paths, resulting in a high Na+ transport number (0.613). The separator can also tolerate folding, bending and extreme temperature under certain circumstances. Full cells with CP@PPC reveal one‐up capacity retention (96.97%) at 2C after 500 cycles compared to cells with CP. The mechanism highlights the merits of electrolyte analogs in separator modification, making a rational design for durable devices in advanced energy storage systems.
Oil-in-water (O/W) wastewater generally contains inorganic salt ions, which cause energy consumption in the process of electric demulsification. To reveal the influence mechanism of inorganic salt ions on the micro movement of oil droplets in O/W emulsion, the electrophoretic migration of oil droplets with different ion concentration was studied based on molecular dynamics simulation. The results showed that Na⁺ adsorbed the negative charge on the surface of the oil droplets while Cl⁻ repelled it, leading to a decrease in the electrophoretic mobility and deformation of the oil droplets with the increase of ion concentration. The inhibitory effect of three inorganic salts on oil droplet electrophoretic migration was MgCl2 > CaCl2 > NaCl. The weak interaction between oil, water and ions was mainly van der Waals interaction. When the NaCl concentration was 0.4 mol/L, the oil-water interfacial tension was at its maximum value of 85.14 mN/m. and the deformation degree of oil droplets reached the minimum values of 0.45. The formation of hydrated ions reduces the freedom of water molecules. The above findings uncovered the effect of inorganic salt ions on the electrophoretic migration of oil droplets in O/W emulsions under a DC electric field, which can provide theoretical guidance for the purification of oily wastewater from the molecular level.
Powdered activated carbon (PAC) is the most widely used adsorbent for removing odorants like 2-methylisoborneol (MIB) for drinking water purification. The hydrophobicity exhibited by the moieties of the carbon structure is known to be important for the adsorption of activated carbon. Here we propose a novel approach for regulating the hydrophobicity of the carbon surface by rearranging carbon atoms without changing the pore structures markedly through thermal transformation using Fe(NO3)3 as the catalyst. Five different PACs were transformed into hydrophobic porous carbons (HPCs) with 2.47–3.00 times the adsorption capacity and faster adsorption rates, accompanied by the surface free energy being decreased by 26.67–36.40%, the IG2/IG1 representing the degree of order being increased by 17.31–53.68%, the C–C(sp2)/C–C(sp3) being increased by 31.9–49.8%, and the oxygen content being decreased by 4.71–8.63%. The increase in ordered planar crystals dominated by sp2 carbons as well as the decrease in the number of heteroatoms in HPCs might be the main reason for its enhanced adsorption of MIB. Simulation based on reactive force field molecular dynamics indicated that MIB molecules tended to be adsorbed in ordered structures. This study provides a novel angle for improving the surface hydrophobicity of activated carbon, which may lead to the development of high-performance adsorbents.
Thermal and hydration effects on mobility of compact and branched organic molecules and a bulky pharmaceutical substance loaded in submonolayer amounts onto mesoporous silica have been elucidated using 1H and 31P solid-state NMR. In all cases, the ambient hydration has a stronger effect than an increase in temperature to 370 K for water-free silica. The effect of hydration depends on the guest and ranges from complete solvation to a silica-water-guest sandwich structure to silica-guest/silica-water pattern. The mobility of the guests under different conditions has been described. The specific structure of the MCM-41 surface allows one to study very slow surface diffusion, a diffusivity of about 10-15 - 10-16 m2/s. The data reported are relevant to any non-functionalized silica, while the method used is applicable to any phosphor-containing guest on any host.
The purpose of wet wipes are cleansing, makeup removing, refreshing
and many other purposes. Wipes can be used as disposable or re-usable
depending upon the material. Spun lace viscose fabric is used in
refreshing wipes which absorbs moisture and retain it for a long period
which is also disposable. One of the major component in wet wipes is
essential oils which are concentrated and cannot be used on the bare
skin. Essential oils are extracted from the herbs, obtained by steam or
hydro-distillation. It can be extracted from all organs of the plant. Each
plant is unique and has its own medicinal and aromatic values.
Essential oils are mixed with glycerol to get a solution which is
miscible with distilled water. Glycerine are colourless, odourless,
sweet taste with a syrup-like consistency. Skin health plays a major
role in the wet wipes where the skin becomes smooth, soft and prevents the acne. Good
health is to handle stress, live a longer and more active life. Considering the values with the
special focus, refreshing wipes are made using carefully selected ingredients that will yield
potential benefits such as uplifting mood, reduce stress and tiredness, calm nerves and help
with concentration.
The potential of mean forces (PMFs) has been determined for an isobutane dimer in various solvent environments such as water, methanol and acetonitrile at a temperature of 298 K and pressure of 1 bar using GROMACS software. All the molecular dynamics (MD) simulations are carried out using a TIP3P water model under a CHARMM36 forcefield. Following Umbrella Sampling technique, PMFs are calculated and analyzed using Weighted Histogram Analysis Method (WHAM) and coordination number of first solvation shell is extracted for all solvents using radial distribution function. The shape of PMFs contains contact minima, solvent-separated minima and desolvation maxima. The values of contact minima are not affected much by solvent environment and found to be at 0.5377, 0.5480 and 0.5495 nm for water, methanol and acetonitrile respectively. The corresponding energy depths are found −0.9134, −0.7080 and −0.5295 kcalmol−1. The variation observed at solvent-separated minima is noticeable and found at 0.9012, 0.9721 and 0.9151 nm for water, methanol and acetonitrile, respectively. The coordination number of the first solvation shell by taking an isobutane molecule as a reference from their center of mass is found to be 28.1, 16.9 and 14.8 for water, methanol and acetonitrile, respectively. There is a soft hydrophobic interaction between isobutane dimer and solvents like methanol and acetonitrile relative to water, might be due to the presence of competitive methyl group of methanol and acetonitrile in the solvent medium.
Sequence-defined peptoids, or N-substituted glycines, are an attractive class of bioispired polymer due to their biostability and efficient synthesis. However, the de novo design of folded peptoids with precise three-dimensional structures has been hindered by limited means to deterministically control backbone conformation. Peptoid folds are generally destabilized by the cis/trans backbone-amide isomerization, and few side-chains are capable of enforcing a specific amide conformation. Here, we show that a novel class of cationic alkyl ammonium ethyl side-chains demonstrates significant enforcement of the cis-amide backbone (Kcis/trans up to 70) using an unexpected ensemble of weak intramolecular CH-O and/or NH-O hydrogen bonds between the side-chain and the backbone carbonyl moieties. These interactions are evidenced by X-ray crystallography, variable-temperature NMR spectroscopy, and DFT calculations. Moreover, these side-chains are inexpensive, structurally diverse, hydrophilic, and can be integrated into longer peptoid sequences via solid-phase synthesis. Notably, we extended these concepts to synthesize a water-soluble peptoid 10-mer that adopts one predominant fold in solution, as determined by multidimensional NMR spectroscopy. This decamer, to the best of our knowledge, is the longest linear peptoid sequence atomically characterized to retain a well-folded structure. These findings fill a critical gap in peptoid folding and should propel the development of peptoid applications in a broad range of contexts, from pharmaceutical to material sciences.
Before reading this essay, go to your kitchen and find a bottle of Italian salad dressing. Get one that’s been sitting still for a while at a fixed temperature—that is, one in thermal equilibrium. You’ll find an oil-rich layer at the top of the bottle and a vinegar-rich layer at the bottom (see Fig. 1). But think for a moment before spreading it over a delicious salad and eating up. That bottle’s in thermal equilibrium, so it’s in a state of maximum entropy. Doesn’t entropy mean “disorder”? No one would call a stack of 50 pennies and 50 dimes disordered if all the dimes were on the top and all the pennies at the bottom. So why is this salad dressing at thermal equilibrium segregated like an ordered stack of coins?
Advanced Manufacturing is a unique book that brings otherwise sparsely treated topics into one space. It covers many types of innovative materials and their applications; including glasses, ceramics, composites, carbon materials, and biomaterials. In addition, it spans the latest developments in manufacturing techniques; including machining, welding, chemical manufacturing, and additive manufacturing, all presented in an informative as well as reader-friendly style.
The process of membrane fusion has been examined by Monte Carlo simulation, and is found to be very different than the conventional
picture. The differences in mechanism lead to several predictions, in particular that fusion is accompanied by transient leakage.
This prediction has recently been verified. Self-consistent field theory is applied to examine the free energy barriers in
the different scenarios.
To develop an understanding of the molecular interactions of polar and nonpolar molecules, we have developed two simple and extremely useful overhead projection demonstrations that help students conceptualize the solubility rules.
Prevailing descriptions of the "hydrophobic interaction" or "hydrophobic effect" are incompatible with relationships found between the structures of various nonpolar solutes and their solvation energies by water and 1-octanol. Previously reported linear relationships between partition coefficient and molecular volume actually result from compensation between relatively irregular solvation energies in water and lipid. In the partitioning of a -CH2- moiety from water into octanol, ΔG298 = -0.54 (±0.01) kcal/mol for favorable solvation by octanol and only +0.18 (±0.01) kcal/mol for disfavorable solvation by water, whereas in the partitioning of a "CH2-equivalent incremental molecular volume" of a rare gas, ΔG298 = -1.58 (±0.14) kcal/mol for favorable octanol solvation and -0.81 (±0.03) kcal/mol for favorable water solvation. These two distinct linear relationships between molecular volume and solvation energy require two bulk-related modes of solute/solvent interaction. Such results appear more consistent with cavity-based models of solvation, such as the general "scaled-particle" theory. Other arguments in support of the "hydrophobic effect" are refuted.
The problem of hydrophobic bonding, i.e., the strong tendency of hydrocarbons in water to aggregate, can be related (at least if the aggregate contains a sufficiently high number of molecules) and is intuitively related to the original problem of the transfer of nonpolar solutes to a nonpolar solvent from water (e.g., transfer of CâHââ from liquid CâHââ to water or from cyclohexane to water). The scaled particle theory, which has been shown to successfully predict the solubility of nonpolar rare gases or hydrocarbons into water and organic solvents from the gaseous state, may be used either to compute the strength of aggregates of hydrocarbons in water (in a modified form), or the transfer of a hydrocarbon from water to its pure liquid phase. Calculations make it apparent that the solvent dimensions are an important parameter in determining the sign of the free energy of transfer for a nonpolar solute from one solvent to another. The structure of the solvent determines the sign of the entropy of transfer. (13 refs.)
The ideas of the first and second papers in this series, which make it possible to interpret entropy data in terms of a physical picture, are applied to binary solutions, and equations are derived relating energy and volume changes when a solution is formed to the entropy change for the process. These equations are tested against data obtained by various authors on mixtures of normal liquids, and on solutions of non‐polar gases in normal solvents. Good general agreement is found, and it is concluded that in such solutions the physical picture of molecules moving in a ``normal'' manner in each others' force fields is adequate. As would be expected, permanent gases, when dissolved in normal liquids, loosen the forces on neighboring solvent molecules producing a solvent reaction which increases the partial molal entropy of the solute. Entropies of vaporization from aqueous solutions diverge strikingly from the normal behavior established for non‐aqueous solutions. The nature of the deviations found for non‐polar solutes in water, together with the large effect of temperature upon them, leads to the idea that the water forms frozen patches or microscopic icebergs around such solute molecules, the extent of the iceberg increasing with the size of the solute molecule. Such icebergs are apparently formed also about the non‐polar parts of the molecules of polar substances such as alcohols and amines dissolved in water, in agreement with Butler's observation that the increasing insolubility of large non‐polar molecules is an entropy effect. The entropies of hydration of ions are discussed from the same point of view, and the conclusion is reached that ions, to an extent which depends on their sizes and charges, may cause a breaking down of water structure as well as a freezing or saturation of the water nearest them. Various phenomena recorded in the literature are interpreted in these terms. The influence of temperature on certain salting‐out coefficients is interpreted in terms of entropy changes. It appears that the salting‐out phenomenon is at least partly a structural effect. It is suggested that structural influences modify the distribution of ions in an electrolyte solution, and reasons are given for postulating the existence of a super‐lattice structure in solutions of LaCl3 and of EuCl3. An example is given of a possible additional influence of structural factors upon reacting tendencies in aqueous solutions.
A simple model is developed for calculation of the difference in free energy (ΔF) between the native and unfolded forms of a protein molecule in solution. A major term in the expression for ΔF arises from the increase in entropy which accompanies unfolding. This term is negative, i.e., it favors the unfolded form. In water, therefore, where a compact globular conformation is stable, local interactions must exist which make a large positive contribution to ΔF. One such interaction in the hydrophobic interaction, which results from the unfavorable arrangement of water molecules which takes place whenever there is contact between water and a non-polar portion of a protein molecule. There are many such contacts when the protein molecule is unfolded, but relatively few in the native state, so that a positive contribution to ΔF results. When amino acids with non-polar side chains are dissolved in water, the same interactions must occur. The magnitude of these interactions can then be estimated from relative solubilities of appropriate amino acids in water and other solvents. Such estimates are made in this paper, and the conclusion is that these hydrophobic interactions alone may be able to account for the instability of an unfolded protein, relative to a suitable globular conformation, in aqueous solution. The model used cannot predict the structure which will be adopted by a given protein molecule in its native state. General considerations suggest, however, that the hydrophobic interactions are compatible with a large variety of structures and that specificity of structure is at least partly due to hydrogen bonds between peptide groups (as well as other polar groups) trapped within the hydrophobic interior.
Analysis of the physical basis and current understanding of hydrophobic interactions. Keywords (Audience): Upper-Division Undergraduate
"A Wiley-Interscience Publication" Incluye bibliografía e índice
The experimental thermodynamic data for the dissolution of five simple hydrocarbon molecules in water were combined with the solute-solvent interaction energy from a computer simulation study to yield data on the enthalpy change of solvent reorganization. Similar data were generated for dissolving these same solute molecules in their respective neat solvents using the equilibrium vapor pressure and the heat of vaporization data for the pure liquid. The enthalpy and the free energy changes upon cavity formation were also estimated using the temperature dependence of the solute-solvent interaction energy. Both the enthalpy and T delta S for cavity formation rapidly increase with temperature in both solvent types, and the free energy of cavity formation can be reproduced accurately by the scaled particle theory over the entire temperature range in all cases. These results indicate that the characteristic structure formation around an inert solute molecule in water produces compensating changes in enthalpy and entropy, and that the hydrophobicity arises mainly from the difference in the excluded volume effect.
The importance of the small size of a water molecule as contributing to the hydrophobic effect is examined from simulations of n-dodecane in different solvents. The earlier observations of the origin of hydrophobicity, derived from cavity formations by Pratt and Pohorille (1992, Proc. Natl. Acad. Sci. USA. 89:2995-2999) and Madan and Lee (1994, Biophys. Chem, 51:279-289), are shown to be largely consistent for a hydrocarbon-induced water pocket. In effect, the small size of a water molecule limits the probability (and hence free energy) of finding an appropriate void in the fluid that will accommodate a solute. In this work a simulated collapse of an n-dodecane molecule in H2O, CCl4, and a water-like Lennard-Jones solvent indicates that the induced entropy and enthalpy changes are qualitatively similar for hydrogen-bonded and Lennard-Jones water solvents. These results suggest that a large part of the hydrophobic response of solutes in aqueous solutions is due to the small size of the solvent. Important quantitative differences between the studied water solvents indicate that the hydrogen-bonded properties for water are still needed to determine the overall hydrophobic response.
Molecular dynamics simulations are used to model the transfer thermodynamics of krypton from the gas phase into water. Extra long, nanosecond simulations are required to reduce the statistical uncertainty of the calculated "solvation" enthalpy to an acceptable level. Thermodynamic integration is used to calculate the "solvation" free energy, which together with the enthalpy is used to calculate the "solvation" entropy. A comparison series of simulations are conducted using a single Lennard-Jones sphere model of water to identify the contribution of hydrogen bonding to the thermodynamic quantities. In contrast to the classical "iceberg" model of hydrophobic hydration, the favorable enthalpy change for the transfer process at room temperature is found to be due primarily to the strong van der Waals interaction between the solute and solvent. Although some stabilization of hydrogen bonding does occur in the solvation shell, this is overshadowed by a destabilization due to packing constraints. Similarly, whereas some of the unfavorable change in entropy is attributed to the reduced rotational motion of the solvation shell waters, the major component is due to a decrease in the number of positional arrangements associated with the translational motions.
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