Pannuru Venkatesu

University of Delhi, Old Delhi, NCT, India

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Publications (37)151.42 Total impact

  • Awanish Kumar, Pannuru Venkatesu
    PROCESS BIOCHEMISTRY 12/2014; · 2.52 Impact Factor
  • Anjeeta Rani, Pannuru Venkatesu
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    ABSTRACT: In present study, an attempt is made to elucidate the effects of various naturally occurring osmolytes and denaturants on BM at pH 7.0. The effects of the varying concentrations of glycerol, sorbitol, sucrose, trehalose, urea and guanidinium chloride (GdnHCl) on structure, stability and activity of BM are explored by fluorescence spectroscopy, circular dichroism (CD), UV-vis spectroscopy and sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). Our experimental observations reveal that glycerol and sorbitol are acting as stabilizers at all concentrations while sucrose and trehalose are found to be destabilizers at lower concentrations, however, acted as stabilizers at higher concentrations. On the other hand, urea and GdnHCl are denaturants except at lower concentrations. There is a direct relationship between activity and conformational stability as the activity data are found to be in accordance with conformational stability parameters (ΔGu, Tm, ΔCp) and BM profile on SDS-PAGE. Copyright © 2014 Elsevier B.V. All rights reserved.
    International Journal of Biological Macromolecules 11/2014; · 3.10 Impact Factor
  • Pannuru Venkatesu, Awanish kumar, Anjeeta Rani
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    ABSTRACT: In this article, we have compared the anions of sodium salts (Is) and ionic liquids (ILs) with the stability and structure of α-chymotrypsin (CT), through fluorescence, thermal fluorescence analysis and circular dichroism (CD) spectroscopy. The experimental results revealed that the Hofmeister series of anions such as SCN‾, SO42ˉ, Cl‾, Br‾, CH3COO‾ and I‾ of Is destabilized the native structure of the CT. On the contrary, the anions such as CH3COO‾, Cl‾ and Br‾ of imidazolium-based IL with fixed cation such as 1-butyl-3-methylimidazolium, [Bmim]+ stabilized the native structure of the CT. The remaining anions of ILs such as SCN‾, HSO4‾, and I‾ acted as denaturing agents for the native structure of CT. Furthermore, molecular docking results show that the imidazolium-cation of the IL enters the sub-domains of the CT and interacts with the ionic residues of the CT, that is Ser217 close to Trp215. This interaction is in well agreement with the fluorescence quenching observed for CT in the presence of [Bmim]+. On the other hand, the destabilizing anion such as SO42ˉwas observed to be directly interacting with Ser195 in the active site of the CT. We have observed that the Hofmeister series effects of anions of either Is or ILs are entirely based on the interaction of the anions with its counterion, that is the cation, with solvent molecules, as well as with the protein surface. Evidently, these interactions vary with co-solvent system and the type of the protein. Hence, the stability of a biomolecule in the presence of the anions may or may not obey Hofmeister series.
    New Journal of Chemistry 11/2014; · 3.16 Impact Factor
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    Awanish Kumar, Pannuru Venkatesu, Mohamed Taha, Ming-Jer Lee
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    ABSTRACT: Amino acids (AAs) combine to form a three-dimensional protein structure and are of very much importance in understanding the biophysical properties of biomolecules. Basically, the nature and the arrangement of the AAs in a protein backbone is only responsible for the individual characteristics of the macromolecule. The AAs in a protein backbone are influenced by the solvent molecules hence, it is very important to have a clear idea on the solubility, stability, and thermodynamic properties of these AAs in various solvents and co-solvents. A basic level of quantifying protein-solvent interactions involve the use of transfer free energies, �ΔGtr from water to solvents. The values of �Gtr for side chains and peptide backbone quantify the thermodynamic consequences of solvating a protein species in a co-solvent solution relative to pure water. Based on the transfer model and experimental Δ�Gtr for these AAs, it has been proposed that these cosolvents exert their effect on protein stability primarily via the protein backbone. The Δ�Gtr of AAs from water to another solvent system will be either favorable or unfavorable. By definition, an unfavorable transfer free energy, Δ�Gtr > 0, means that the protein becomes solvophobic on transfer to a solvent, whereas a favorable transfer free energy, Δ�Gtr < 0, represents that the protein becomes solvophilic on transfer to a solvent. The sign and magnitude of the measured Δ�Gtr quantifies the protein response to changes in solvent quality. Therefore, this review will provide the basis of a universal mechanism for co-solvent-mediated (that includes the new novel biocompatible ionic liquids (ILs)) protein stabilization and destabilization as the protein backbone is shared by all proteins, regardless of side chain sequence.
    Current Biochemical Engineering. 07/2014; 1(2):125-140 (16).
  • Awanish Kumar, Anjeeta Rani, Pannuru Venkatesu, Anil Kumar
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    ABSTRACT: Significant non-reversible two-state denaturation was observed for proteins such as myoglobin (Mb) and α-chymotrypsin (CT) with decreasing temperature in the presence of 1-butyl-3-methylimidazolium-based ([C4mim](+)X(-)) ionic liquids (ILs) with various anions (X(-)). Interestingly, for the first time, ILs having acetate and bromide anions were proven to counteract the cold-induced unfolding of proteins.
    Physical Chemistry Chemical Physics 06/2014; · 4.20 Impact Factor
  • Pankaj Attri, Indrani Jha, Eun Ha Choi, Pannuru Venkatesu
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    ABSTRACT: Protein stability in ionic solution depends on the delicate balance between protein-ion and ion-ion interactions. To address the ion specific effects on the protein, we have examined the stability of myoglobin (Mb) in the presence of buffer and ammonium-based ionic liquids (ILs) (50% (v/v)). Here, fluorescence and circular dichroism (CD) spectroscopy experiments are used to study the influence of ILs on structure and stability of Mb. Our experimental results reveal that more viscous ILs (sulphate or phosphate ions) are stabilizers and therefore more biocompatible for Mb structure. Surprisingly, the less viscous ILs such as acetate anion based ILs are destabilizers for the native structure of Mb. Our results explicitly elucidate that anion variation has significant influence on Mb stability efficiency than cation variation. This study provides insight into anion effects on protein stability and explains that the intrasolvent interactions can be leveraged to enhance the stability.
    International Journal of Biological Macromolecules 05/2014; · 3.10 Impact Factor
  • Reddicherla Umapathia, Pankaj Attri, Pannuru Venkatesu
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    ABSTRACT: Experimental densities (ρ), ultrasonic sound velocities (u), viscosities () and refractive indices (nD) of binary mixtures of ammonium-based ionic liquids (ILs) such as diethylammonium acetate (DEAA) [(CH3CH2)2NH][CH3COO], triethylammonium acetate (TEAA) [(CH3CH2)3NH][CH3COO], diethylammonium hydrogen sulfate (DEAS) [(CH3CH2)2NH][HSO4], triethylammonium hydrogen sulfate (TEAS) [(CH3CH2)3NH][HSO4], trimethylammonium acetate (TMAA) [(CH3)3NH][CH3COO] and trimethylammonium hydrogen sulfate (TMAS) [(CH3)3NH][HSO4] with water are reported over the wide composition range at 25 0C under atmospheric pressure. The excess molar volumes (VE), deviation in isentropic compressibilities (Δs), deviation in viscosities (Δ) and deviation in refractive indices (ΔnD) are calculated from experimental values and are correlated by Redlich-Kister polynomial equations. The VE and Δs values for the aforesaid systems are negative over the entire composition range while the Δ and ΔnD values are positive under the same experimental conditions. The intermolecular interactions and structural effects were analyzed on the basis of measured and derived properties. A qualitative analysis of the results is discussed in terms of the ion-dipole, ion-pair interactions and hydrogen bonding between ILs and water. Furthermore, the hydrogen bonding features between ILs with water were analyzed by using a molecular modeling program with the help of HyperChem7.
    The Journal of Physical Chemistry B 05/2014; · 3.38 Impact Factor
  • Indrani Jha, Pankaj Attri, Pannuru Venkatesu
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    ABSTRACT: The nature of solvent-biomolecule interactions is generally weak and non-specific. The addition of ionic liquids (ILs), which have emerged as a new class of solvents, strengthen the stability of some proteins whereas the same ILs weaken the stability of some other proteins. Although ILs are commonly used for the stabilization of biomolecules, the bimolecular interactions of their stabilization-destabilization is still an active subject of considerable interest and studies on this topic have been limited. To reveal the impact of ILs on the stability of proteins, a series of protic ILs possessing a tetra-alkyl ammonium cation [R4N](+) with a hydroxide [OH](-) anion were synthesized. In this study, we report the structural stability of heme proteins such as myoglobin (Mb) and hemoglobin (Hb) in a series of ammonium-based ILs such as tetramethyl ammonium hydroxide [(CH3)4N](+)[OH](-) (TMAH), tetraethyl ammonium hydroxide [(C2H5)4N](+)[OH](-) (TEAH), tetrapropyl ammonium hydroxide [(C3H7)4N](+)[OH](-) (TPAH) and tetrabutyl ammonium hydroxide [(C4H9)4N](+)[OH](-) (TBAH) by fluorescence and circular dichroism (CD) spectroscopic studies. Our experimental results reveal that less viscous ILs carrying smaller alkyl chain such as TMAH are strong destabilizers of the heme proteins as compared to the ILs carrying bulkier alkyl chains which are more viscous ILs, such as TBAH. Therefore, our results demonstrate that the addition of these ILs to the heme proteins decreases their thermal stability allowing the protein to be in an unfolded state at lower temperatures. Further, we describe the molecular-structural interaction of the heme proteins with the ILs (molecule like a ligand) by the PatchDocking method.
    Physical Chemistry Chemical Physics 02/2014; · 4.20 Impact Factor
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    ABSTRACT: In this work, we have explored the thermophysical properties of tetraalkylammonium hydroxide ionic liquids (ILs) such as tetrapropylammonium hydroxide (TPAH) and tetrabutylammonium hydroxide (TBAH) with isomers of butanol (1-butanol, 2-butanol and 2-methyl-2-propanol) within the temperature range 293.15-313.15 K, with interval of 5 K and over the varied concentration range of ILs. The molecular interactions between ILs and butanol isomers are essential for understanding the function of ILs in related measures and excess functions are sensitive probe for the molecular interactions. Therefore, we calculated the excess molar volume (V(E) ) and the deviation in isentropic compressibility (Δκs ) using the experimental values such as densities (ρ) and ultrasonic sound velocities (u) that are measured over the whole compositions range at five different temperatures (293.15, 298.15, 303.15, 308.15 and 313.15 K) and atmospheric pressure. These excess functions were adequately correlated by using the Redlich-Kister polynomial equation. It was observed that for all studied systems, the V(E) and Δκs values are negative for the whole composition range at 293.15 K. And, the excess function follows the sequence: 2-butanol>1-butanol>2-methyl-2-propanol, which reveals that (primary or secondary or tertiary) position of hydroxyl group influence the magnitude of interactions with ILs. The negative values of excess functions are contributions from the ion-dipole interaction, hydrogen bonding and packing efficiency between the ILs and butanol isomers. Hence, the position of hydroxyl group plays an important role in the interactions with ILs. The hydrogen bonding features between ILs and alcohols were analysed using molecular modelling program by using HyperChem 7.
    PLoS ONE 01/2014; 9(1):e86530. · 3.53 Impact Factor
  • Awanish Kumar, Pannuru Venkatesu
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    ABSTRACT: Understanding the behavior of Hofmeister anions of ionic liquids (ILs) on protein stability helps to shed light on how the anions interact with proteins in aqueous solution and is a long standing object for chemistry and biochemistry. Ions effects play a major role in understanding the physicochemical and biological phenomenon that undertakes the protein folding/unfolding and refolding process. Despite the generality of these effects, our understanding of ions at the molecular-level is still limited. This review offers a tour through past successful investigations and presents a challenge in current research in the field to reassess the possibilities of ions and to apply new strategies. This review highlights on the stability behavior of the proteins and also comparisons of our past research work in the Hofmeister series of ILs. Furthermore, we specifically focus on the critical discussion on the recent findings with existing results and their implications, along with our understanding of the Hofmeister series of anions of ILs on biomolecular stability. A detailed examination of the difference between selective proteins can provide a better understanding of the molecular mechanism of protein folding/unfolding in the presence of the Hofmeister series of ions of ILs.
    International journal of biological macromolecules 11/2013; · 2.37 Impact Factor
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    ABSTRACT: In recent years, ionic liquids (ILs) represent a new class of biocompatible co-solvents for biomolecules. In this work, we report the apparent transfer free energies (ΔG'tr) for six amino acids (AA) from water to aqueous solutions of six ammonium based ILs (diethylammonium acetate (DEAA), diethylammonium sulfate (DEAS), triethyl ammonium acetate (TEAA), triethylammonium sulfate (TEAS), triethylammonium dihydrogen phosphate (TEAP), and trimethylammonium acetate (TMAA)) through solubility measurements, as a function of IL concentration at 298.15 K under atmospheric pressure. Salting-out effect was found for AA in aqueous IL solutions with increasing IL concentrations. In addition, we observed positive values of ΔG'tr for AA from water to ILs, indicating that the interactions between ILs and AA are unfavorable. From the obtained results, we found that the selected ammonium based ILs act as stabilizers for the structure of AA.
    Protein and Peptide Letters 07/2013; · 1.74 Impact Factor
  • Pankaj Attri, Pannuru Venkatesu
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    ABSTRACT: Ammonium based ionic liquids (ILs) are biocompatible co-solvents that stabilize the native state of proteins. Experimentally, we have explored the stability of α-chymotrypsin (CT) in the presence of nine ILs, i.e., diethylammonium acetate (DEAA), diethylammonium hydrogen sulfate (DEAS), diethylammonium dihydrogen phosphate (DEAP), triethylammonium acetate (TEAA), triethylammonium hydrogen sulfate (TEAS), triethylammonium dihydrogen phosphate (TEAP), trimethylammonium acetate (TMAA), trimethylammonium hydrogen sulfate (TMAS), trimethylammonium dihydrogen phosphate (TMAP). Thermodynamic folding properties such as transition temperature (Tm), Gibbs free energy change of unfolding (ΔGU), enthalpy change (ΔH) and heat capacity change (ΔCp) of CT in ILs are obtained by fluorescence spectra analysis. Fluorescence and circular dichroism (CD) spectroscopy experiments were performed to probe CT stabilization and structural changes in the presence of ILs. Our experimental results suggest that the ILs act as stabilizers for the CT structure and the stability of CT depends on the structural arrangement of the ions of ILs. Our experimental results reveal that ILs (DEAA, DEAS and DEAP) having more hydrophobic ammonium cations [DEA+] are weak stabilizers for CT, while trimethyl ammonium cations [TMA+] ILs having small alkyl chain length such as TMAA, TMAS and TMAP are strong stabilizers and therefore more biocompatible for the native structure of CT.
    PROCESS BIOCHEMISTRY 03/2013; 48(3):462–470. · 2.52 Impact Factor
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    ABSTRACT: In this article, we investigate the effect of guanidinium hydrochloride (GdnHCl) on the phase transition temperature of poly (N-isopropylacrylamide) (PNIPAM) in aqueous solution with the aid of fluorescence spectroscopy, viscosity (η), and dynamic light scattering (DLS) measurements. Temperature dependent fluorescence intensity measurements have been employed successfully to determine the conformational change of PNIPAM through evaluating the Gibbs free energy changes. Additionally, direct hydrogen bonding formation between GdnHCl and PNIPAM has been confirmed by Fourier transform infrared (FTIR) spectroscopy measurements at various concentrations of GdnHCl. The intermolecular interactions were also studied in terms of amide I band analysis, which reveals the interruption of hydrated coil conformation of PNIPAM. The degree of destabilization of PNIPAM progressively increases with increasing concentration of the denaturant.
    Polymer 01/2013; 54(2):791–797. · 3.77 Impact Factor
  • T. Vasantha, Pankaj Attri, Pannuru Venkatesu, R.S. Rama Devi
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    ABSTRACT: In this article, we have reported the solubilities, apparent transfer free energies (ΔG′tr) and UV-visible absorption measurements of glycine peptides (GPs), such as glycine (Gly), diglycine (Gly2), and cyclic glycylglycine (c(GG)) in aqueous ionic liquids (ILs), bearing sulfate and phosphate anions with ammonium cation, at T = 298.15 K. Values of solubility were obtained from density (ρ) measurements of GPs in water and in aqueous ILs. The ammonium ILs such as diethylammonium hydrogen sulfate (DEAS) [(CH3CH2)2NH][HSO4], triethylammonium hydrogen sulfate (TEAS) [(CH3CH2)3NH][HSO4], and triethylammonium dihydrogen phosphate (TEAP) [(CH3CH2)3NH][H2PO4] have been used in the present study. We observed the positive values of ΔG′tr for Gly, Gly2, and c(GG) from water to ILs. These results reveal that the unfavourable interactions are dominated between ILs and the GPs. This indicates that the ammonium based ILs stabilize the GP structure. Further, we have used the ΔG′tr results to evaluate the transfer free energies (Δg′tr) contribution of the peptide backbone unit, also known as glycyl residue, (–CH2CONH–) as function of ILs concentration. Our results suggest that all the investigated ammonium ILs are compatible with GPs and act as stabilizers for GPs structure through exclusion of ILs from GPs’ surface. Furthermore, UV-vis spectrophotometer measurements are used as evidence for the stability of GPs in aqueous ILs at T = 298.15 K.
    The Journal of Chemical Thermodynamics 01/2013; 56:21–31. · 2.42 Impact Factor
  • Awanish Kumar, Pannuru Venkatesu
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    ABSTRACT: The self-aggregation and thermal instability of insulin (In) was considerably controlled in the presence of ammonium-based protic ionic liquids (PILs). The thermal stability of In in PILs was observed using fluorescence and absorption spectroscopy of the Tyr environment of the biomolecule. Additionally, from circular dichroism (CD) measurements, we observed the shift in the wavelength towards lower values in the presence of PILs, which indicates the formation of monomers of In, further evidently supported by dynamic light scattering (DLS) measurements. Surprisingly, it is the monomeric form of the In that exists in the active form. For the first time, ammonium-based PILs have been shown to be novel solvents for In, which prevent it from associating into an inactive form and also stabilizes In against thermal influence.
    RSC Advances 12/2012; 3(2):362-367. · 3.71 Impact Factor
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    ABSTRACT: Understanding the folding process of proteins or polypeptides in co-solvents is a fascinating and critical issue in biophysical chemistry. In recent years, ionic liquids (ILs) represent a versatility of the new class of co-solvents. To quantify the bimolecular interactions of amino acids (AA), such as l-alanine (Ala) and l-valine (Val) with biocompatible ILs, we report the apparent transfer free energies (ΔG′tr) for AA from water to aqueous solutions of six ammonium based ILs (diethylammonium acetate (DEAA), diethylammonium sulfate (DEAS), triethyl ammonium acetate (TEAA), triethylammonium sulfate (TEAS), triethylammonium dihydrogen phosphate (TEAP), and trimethylammonium acetate (TMAA)) through solubility measurements, as a function of IL concentration at 298.15 K under atmospheric pressure. Salting-out effect was found for AA in aqueous IL solutions with increasing IL concentrations. In addition, we observed positive values of ΔG′tr for Ala and Val from water to ILs, indicating that the interactions between ILs and AA are unfavorable. From the solubility results, we envisage that the selected ammonium based-ILs provide stability to the structure of AA. Further, the stability of AA has been studied by means of the UV–vis spectroscopy.
    Fluid Phase Equilibria 12/2012; 335:39–45. · 2.24 Impact Factor
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    ABSTRACT: We report the synthesis and characterisation of a series of ammonium ionic liquids (ILs) containing acetate and sulphate anions with alkyl ammonium cation. To understand the thermophysical properties of these synthesised ILs with polar solvent N-methyl-2-pyrrolidone (NMP), precise measurements such as densities (ρ), speed of sound (u), and viscosity (η) over the entire mole fraction range have been measured at 5 K intervals within the temperature range of (298.15 to 313.15) K under atmospheric pressure. The excess molar volume (VE), the deviation in isentropic compressibility (Δκs), and deviation in viscosity (Δη) were predicted using these temperature dependence properties as a function of the concentration of ILs. The Redlich–Kister polynomial was used to correlate the results. The ILs investigated in the present work included diethylammonium acetate (DEAA) [(CH3CH2)2NH][CH3COO], triethylammonium acetate (TEAA) [(CH3CH2)3NH][CH3COO], diethylammonium hydrogen sulphate (DEAS) [(CH3CH2)2NH][HSO4], and triethylammonium hydrogen sulphate (TEAS) [(CH3CH2)3NH][HSO4]. The intermolecular interactions and structural effects were analysed on the basis of the measured and the derived properties. The information reported here in terms of ion–dipole interactions, ion-pair interactions and hydrogen bonding between ILs and NMP, elucidates the influences of ions and also the temperature effects on the thermophysical properties.
    The Journal of Chemical Thermodynamics 11/2012; 54:223–237. · 2.42 Impact Factor
  • Awanish Kumar, P. Madhusudhana Reddy, Pannuru Venkatesu
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    ABSTRACT: Interestingly, various behaviors of ionic liquids (ILs) having different cation chains with a common anion is observed in the coexistence curve of isobutyric acid–water (IBW). The critical region of IBW was found to increase in the presence of aliphatic chain 1-hexyl-3-methyl-imidazolium tetrafluoroborate [C6mim][BF4], (IL-1) whereas the critical region decreased in the presence of aromatic chain 1-benzyl-3-methylimidazolium tetrafluoroborate [Bnmim][BF4], (IL-2). Adding 0.5–2.0 mg ml−1 of IL-1 or IL-2 to IBW caused the critical temperature (Tc) to decrease by 0.553–2.898 K (for IL-1) and to increase by 0.502–1.664 K (for IL-2). The critical exponent (β) increases with increasing the IL concentrations, which are fully renormalized critical exponents. Further, our dynamic light scattering (DLS) results for the binary critical solution of IBW indicate that there exists a fluctuation in the local density that contributes significantly to the fluctuations in the scattered intensity at Tc. The variations in fluctuations are found to be pronounced in the presence of IL as an impurity. The reason for this behavior may be the formation of large water clusters with the neighboring molecules of ILs at Tc. This indicates that the IL entangles with the both coexisting phases, thereby, the IL strongly interacts with the neighboring solvent molecules. In addition, we report the fluorescence spectroscopy data for the critical mixture of IBW and its mixture with ILs as impurities using Nile Red as a fluorescent probe. Noticeable transitions of the two phases were detected at Tc through fluorescence technique. The observed variations in the fluorescence intensities with temperature predict unambiguously the formation of the solvation structure at Tc for the pure critical mixture as well as in presence of ILs.
    New Journal of Chemistry 10/2012; 36(11):2266-2279. · 3.16 Impact Factor
  • T Vasantha, Pankaj Attri, Pannuru Venkatesu, R S Rama Devi
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    ABSTRACT: Protein folding/unfolding is a fascinating study in the presence of cosolvents, which protect/disrupt the native structure of protein, respectively. The structure and stability of proteins and their functional groups may be modulated by the addition of cosolvents. Ionic liquids (ILs) are finding a vast array of applications as novel cosolvents for a wide variety of biochemical processes that include protein folding. Here, the systematic and quantitative apparent transfer free energies (ΔG'(tr)) of protein model compounds from water to ILs through solubility measurements as a function of IL concentration at 25 °C have been exploited to quantify and interpret biomolecular interactions between model compounds of glycine peptides (GPs) with ammonium based ILs. The investigated aqueous systems consist of zwitterionic glycine peptides: glycine (Gly), diglycine (Gly(2)), triglycine (Gly(3)), tetraglycine (Gly(4)), and cyclic glycylglycine (c(GG)) in the presence of six ILs such as diethylammonium acetate (DEAA), diethylammonium hydrogen sulfate (DEAS), triethylammonium acetate (TEAA), triethylammonium hydrogen sulfate (TEAS), triethylammonium dihydrogen phosphate (TEAP), and trimethylammonium acetate (TMAA). We have observed positive values of ΔG'(tr) for GPs from water to ILs, indicating that interactions between ILs and GPs are unfavorable, which leads to stabilization of the structure of model protein compounds. Moreover, our experimental data ΔG'(tr) is used to obtain transfer free energies (Δg'(tr)) of the peptide backbone unit (or glycyl unit) (-CH(2)C═ONH-), which is the most numerous group in globular proteins, from water to IL solutions. To obtain the mechanism events of the ILs' role in enhancing the stability of the model compounds, we have further obtained m-values for GPs from solubility limits. These results explicitly elucidate that all alkyl ammonium ILs act as stabilizers for model compounds through the exclusion of ILs from model compounds of proteins and also reflect the effect of alkyl chain on the stability of protein model compounds.
    The Journal of Physical Chemistry B 09/2012; 116(39):11968-78. · 3.38 Impact Factor
  • Pankaj Attri, Pannuru Venkatesu
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    ABSTRACT: In this article, we present the synthesis of a series ionic liquids (ILs) having different kosmotropicity including dihydrogen phosphate (H2PO4-) and hydrogen sulphate (HSO4-) as anions and chaotropic cation such as alkylammonium. Here, we have investigated the biomolecular interactions and related associated structural changes of succinylated Con A (S Con A) with alkylammonium ILs by using several biophysical techniques including circular dichroism (CD) and fluorescence. The ILs studied in the present research includes diethylammonium dihydrogen phosphate [(CH3CH2)2NH+][H2PO4-] (DEAP), diethylammonium hydrogen sulphate [(CH3CH2)2NH+][HSO4-] (DEAS), triethylammonium dihydrogen phosphate [(CH3CH2)3NH+][H2PO4-] (TEAP) and triethylammonium hydrogen sulphate [(CH3CH2)3NH+][HSO4-] (TEAS). We observed that all ILs have a dominant contribution to the stabilization of the native structure of the S Con A. Our experimental results distinctly demonstrate that the long alkyl chain IL TEAP is a strong stabilizer and therefore more biocompatible for S Con A. Furthermore, the results reveal that phosphate anions of ILs are strong stabilizers and acted as effective refolding enhancers for thermally denatured protein structure, whereas the protein was not refolded in the sulphate anions of ILs. These findings suggest a new generation of protein stabilizers that can be applied to other protein folding studies and biological systems.
    The Journal of Chemical Thermodynamics 09/2012; 52:78–88. · 2.42 Impact Factor