Science topics: Chemical KineticsKinetics

Science topic

# Kinetics - Science topic

The rate dynamics in chemical or physical systems.

Questions related to Kinetics

I'm having trouble understanding my kinetic data. After deriving the velocity for every substrate concentration, I get a sigmoidal curve. I used the Hill equation in Prism to fit my plot, and the hill coefficient h is bigger than the amount of subunits in my protein complex. Is this possible?

I am getting a rate coefficient (Barts-Widom Phenomenological) to be zero for a unimolecular decomposition reaction. Similar reaction with another conformer of the same molecule gives some rate coefficient value. Kindly help.

Hi, here is data from the experiments. I am a bit curious how to get the qe from this experimental data. Could you please help me to solve this as I want to use this data to study the kinetics of the adsorption? Thank you.

Time (min) Co (ppm) Ct (ppm) qt (mg/g) Ce (ppm) qe (mg/g) ln(qe-qt)

0 100 0 125

5 100 44.6 69.25

15 100 35.46 80.675

30 100 10.62 111.725

60 100 0.29 124.6375

90 100 0.18 124.775

120 100 0.21 124.7375

150 100 0.19 124.7625

Hi, I would appreciate it if you could explain to me which equation is correct for the second-order reaction. In the most textbooks I see "K" instead of "2K" in the equation. Please also see the attached pictures.

Regards,

I basically have normalized fluorescence data generated from a series of protein dilutions. I need to calculate K, K should be the same in all dilutions, thus the need for a global fitting approach. I have been using XLfit, but would like to move into a script format. Thanks in advance! Thus far, I found the package renz, but to my understanding, it does not accomodate for global fitting. Thanks in advance!

I have stored the cm5 chip in 50 mL of HBS-EP buffer pH 7.0 at 4°C... which buffer can be used for long-term storage of the chip?

Hi everyone,

I am measuring the activity of some mitochondrial enzymes, by measuring the oxidation/reduction of relevant substrate using spectrophotometer. However, after analysis, my enzymatic activity (nmol/min/mg) becomes a negative value (not always, but most of times).

Is this because my analytes are being used (thus decreased) so their absorbances decrease?

Another question; if the extinction cofficient of my analyte in 340 nm is 6.22 mM-1.cm-1, and the length of cuvette is 0.6 cm, and the concentration of my analyte is 0.1 mM, how should I calculate my enzymatic activity in nmol/min/mg?

Big thanks in advance

I have applied both pseudo first and pseudo second order linear models on my data. Calculated and experimental qe values of pseudo first order are very near to each other. However, in pseudo second order there is striking difference in qe values of experiment and the ones calculated from graph. How can I justify this occurrence? Also R2 value is very good even in Pseudo second order.

Can anyone please assist me to remove this confusion??

I am performing pesudo first order kinetics. In that, I have to plot a graph between ln(qe-qt) and time. SInce the last value of qt is qe, we cannot find ln for that value. How to proceed with the data then.

Also my ln(qt-qe) values are positive whereas in literature, they have shown negative value. Is this a concern?

Thanks for help!

I am trying to simulate methane combustion in an industrial high-pressure gas turbine combustor using the species transport model in fluent with detailed GRI mech 3 mechanism but I get no combustion. I also patch the temperature to a high value.

Has anyone worked with Detailed methane-air combustion in Ansys Fluent?

Why does the same object weigh more when it is hot than when it is cold?

The reason why hot objects are heavier is because E=mc^2. If you have absolutely identical objects that have the same weight exactly when they are at same temperature, then when one object is heated, it will weigh more. This is because the gravitational force depends on the stress energy tensor in general relativity. The stress energy tensor 00 component is the total energy of the body, which includes the rest mass plus the kinetic energy of the object. Temperature differences means that there is a different amount of kinetic energy in the motion of the atoms of the two bodies.

How is it describable by massless photon (electromagnetic energy)?

In classical mechanics, "heat is certainly not a substance in the same sense as mass. Mass can be detected by means of scales, but what of heat? Does a piece of iron weigh more when red-hot than when ice-cold? Experiment shows that it does not. If heat is a substance at all, it is a weightless one". A. EINSTEIN AND L. INFELD, THE EVOLUTION OF PHYSICS, Page 43

Einstein later explained it as follow: “Energy, at any rate kinetic energy, resists motion in the same way as ponderable masses. Is this also true of all kinds of energy? The theory of relativity deduces, from its fundamental assumption, a clear and convincing answer to this question, an answer again of a quantitative character: all energy resists change of motion; all energy behaves like matter; a piece of iron weighs more when red-hot than when cool; radiation traveling through space and emitted from the sun contains energy and therefore has mass; the sun and all radiating stars lose mass by emitting radiation. This conclusion, quite general in character, is an important achievement of the theory of relativity and fits all facts upon which it has been tested". A. EINSTEIN AND L. INFELD, THE EVOLUTION OF PHYSICS, Page 208

The concentration of my protein is 14 μM and the K

_{d}is 168 nM. I want to have the ligand in excess, but I am not sure how to go about it.- His-tagged protein immobilized a on Ni coated NTA chip.
- Both the reference channel and ligand bound channel shows binding with analyte (ribosome)
- negative RU in the resultant curve.
- Reference channel is Ni free.
- Running buffer contains hepes,NaCl,EDTA,Mg(OAc)2
- Both the ligand and analyte are prepared in the running buffer.
- Reference channel was tried to be coated with BSA and still it's showing non-specific binding.
- Tris buffer as running nuffer gave the same non-specific binding but the resultant curve gave positive RU. As suggested in some paper I am using Hepes Buffer now. If anyone has any idea please suggest me a way.

Hello!

Kinetic research in the field of curing process is of great interest for me. It is okay, when some of epoxy resin based systems can be described in terms of usual second (n) order reaction models with additional autocatalysis and/or deceleration terms. Sometime we need to use so called diffusion factor function if reaction is complicated by glass transition temperature and deceleration term in usual from doesn‘t give us a good result of fitting.

**I would like to know how do you usually start your model planing? I just interested in the way you calculate you model: directly with all terms or by part.**

**How can I find the best diffusion factor function?**

**Very many regards in advance**

Please provide the corresponding reference(s) supporting the information.

I need to fit a transient absorption kinetics, starting from -500 fs to 4000 fs. Around time-zero, it has a Gaussian function due to instrument response (region-1) and from about 100 fs (to 4000 fs) it shows the actual exponential kinetics (region-2). I need to fit both the region simultaneously in Origin (i.e. deconvolution around time-zero and exponential growth(/decay) afterwards). Please suggest how do I perform the fit in Origin? Thanks.

Influence of ligand on an heterogeneous catalyst surface reactivity

I am looking for a scientific explanation for the anomalous values of Avrami exponents. Regrading the literature, the typical values of Avrami exponent have to be between 1 and 4. Different Avrami values demonstrate the different mechanisms of crystallization (Phase Transformation), including nucleation rate, growth rate, and dimensionality of the growth. Meanwhile, we obtained some anomalous values of Avrami exponents around 5, we appreciate any contribution in finding meaningful explanations.

Hi,

Recently, I have been working on the adsorption of several dyes onto chitosan hydrogel. The adsorption is conducted at acidic conditions. Chitosan has amino groups, which can be protonated at acidic conditions to form NH3+. Meanwhile, dyes have sulfonic groups (SO3-), which can be attracted to chitosan's NH3+ groups through electrostatic attraction.

From these basic ideas, one can tell that the adsorption is chemisorption.

Now, moving onto adsorption kinetics analysis. First of all, I tried a linear regression method to see whether Lavergren's pseudo-first-order or Ho's pseudo-second-order model fits better. Similar to thousands of other papers, Prof.Ho's PSO model fitted my experimental data like a charm with R2 very close to 1. Meanwhile, PFO model only has a R2 of around 0.85 - 0.90. Bam! My adsorption mechanism is truly chemisorption.

But then, I found several papers using non-linear regression method, which gives a much improved fitting accuracy for Lavergren's PFO model. I tried this non-linear regression method using computer simulation and my PFO model turned out to be the better-fitted model than PSO.

So right now, I am a bit confused. After checking the computer simulation several times, I am pretty confident that the adsorption mechanism follow Lavergren's Pseudo-first-order model, which is rare for liquid-solid adsorption. Most researchers claim that PFO model is only for physical exchange, while PSO model is for chemical interaction (e.g electrostatic attraction in my case), but they didn't provide good enough justification. I have a feeling that many papers on adsorption cannot distinguish well the theoretical difference between PFO and PSO models.. Can a chemisorption mechanism folllow PFO model, or does it always have to be PSO?

Sorry for the long question... Any advice or suggestion is greatly appreciated! Thanks so much.

Hi all,

I am analyzing some kinetic data, my data come from sorption of Heavy metals onto biochar (carbon material). Since it is recomended not to use the linearized kinetic models due to the introduction of errors in the parameters estimation I went directly for the non-linear first and second order kinetic models as are the most used.

I assesed the best fit by the standard error distribution and the correlation between the predicted and experimental values with both models. Overall my results indicate that second order model suits better my data, the correlation coefficients are very close to one. However I am not sure if that is enough as to say that second order model fitted better, because first order was very high as well the difference in correlation coefficient between both could be as small as of 0.001 in some cases. Additionally the curves obtained pretty much overlap one to each other..so I am doubting that I could say that one model describes better my data to another. How it can be possible that both models look so similar on my data? The initial concentration I used is 0.5 mg/L is maybe due to the low concentration of the sorbate?

Any paper that could help me on this would be very welcome

Regards

Rosa

We know that these elements are non-carbide formers. Therefore, C is more likely to be present in the solution which should make the austenite more stable. By this logic, adding these elements should make austenite stable up to an even lower temperature.

Hello fellow scientists,

I have some additional questions about the dissociation constant for a protein binding ligand.

My main questions is if the protein concentration is much greater than the K

_{D}and the ligand concentration is still in excess of the K_D how much protein is bound?For a Protein binding a ligand, we have the relationship:

P + L ⇌ PL . This has forward and reverse rates of binding, and ...

K

_{D}= {[P] * [L]} / [PL],The fraction of protein bound (F

_{PL}) will be:F

_{PL}= [PL] / ([P] + [PL]) = {[L] / ([L] + K_{D})}If the ligand concentration is some multiple integer n of the K

_{D}we get this cool relationship:[L] = n * K

_{D}; n = 1, 2, 3, ... etc.F

_{PL}= (n * K_{D}) / (n*K_{D}+ K_{D})= n / (n + 1)

What they teach you in school is that if the ligand concentration is at the K

_{D}, n = 1 then half the protein is bound: 1 / (1 + 1) = 1 / 2. This relationship also tells you that if [L] = 9 * K_{D}then 90% of the protein is bound. One can plot this relationship as I have.

So I have some questions assuming a reasonable good ligand interaction with K

_{D}= 10 µM,(A) If [L] = 9 * K

_{D}, and fixed protein concentration = K_{D}= 10 µM, how much protein is bound?I think that 90% of the protein is bound.

B) Say you are a structural biologist and you need more ligand and protein than the K

_{D}at 10 µM,If [L] = 500 µM (that is 50K

_{D}) and initial protein concentration is 100 µM (that is 10K_{D}), then how much protein is bound?Given the relationship I derived, {50 / (50 + 1)} = 98% of the protein should be bound.

But the protein concentration is beyond the K

_{D}so can that even be correct?I am working with HPLC detection of ceftiofur, but could not start as I am finding it difficult to dissolve it in water. I am getting a white color solution in acetonitrile and methanol. Is it normal? Are there any other solvents?

Good-day! Some researchers mention using Hydroquinone solution as a polymerization inhibitor in acrylic acid. How this solution can be prepared ?

What is the CAS number of the starting material involved. Thank you so much !!

A mechanism is moving in a particular pattern. There is a real time video of the same with red color markers are stick to each links. Is there any image processing tool or software which can capture the movement of links and give its change in position, velocity and acceleration? So that the results can be used to co relate rigid body/ multibody dynamic model results.

I am using KinTek software to do a kinetic fitting. I have determined kinetics of the formations of several species in the time course of 5min and established a model for the enzyme (just as an example: A = B = C = D). I already know that B is always below the detection limit of the instrument during the reaction. Is there a way to restrict the amount of B to lower than the detection limit (such as 0.01 uM) in the software? I only find restrictions for kinetic constants and the starting concentration for species. If there is not a way, is it appropriate to import a sudo-data set (such as a constant amount of 0.005 uM B at each time point, with a sigma value of 0.005) for fitting?

We applied the weber and morris model for evaluating the kinetics process. so negative should obtained but in paper negative value does't mentionad. So help ion this regard

Dear colleagues!

Due to the strong irreversible inhibition of the enzyme I have difficulties with the calculation of Kobs.

The FRET scan measurement units changes only by 30-60 units during full reaction time, while the noice is +/- 25 units.

How to check kobs in case of so strong inhibitory activity?

Or C 's reaction with B will be limited or lesser ?

Is it reliable to use TLC densitometry for calculating kinetics of a reaction and is there any previous work that uses TLC densitometry for predicting kinetics of a reaction?

I have a question in regard of the mixture of the apo- and holo-forms of an enzyme.

I know that the apoenzyme should be inactive while the activity of the holoenzyme is in correlation with the heme content. The activity increases as a result of the reconstitution of the enzyme with the heme.

However, is there any information about the influence of an apoenzyme or any other protein on the turnover rates of holoenzymes?

Hey guys!

Im interest in looking into the possible amplified stimuli we can get from ballistic training via the eccentric or absorption phase. If you know of any good studies that report loaded jump squat/olympic lift absorption external/interal kinetics then please do share. Also keen to see what people think of using ballistic training as a possible strength training modality with an increased mechanical power element.

Dear experts,

I am dealing with the synthesis and characterization of PIR foams. In particular, I am monitoring the kinetics of these foams by FTIR (please find the spectra attached below). As well-known from the literature, the asymmetric CH stretching band at 2972 cm-1 (which remains constant during the reaction) is typically used as internal reference band to correct the density changes during the foaming process. In the same way, my question is if you know from the literature some reference band that may be used for PIR to the same purpose.

Please note that for PU a polyether polyol is used, while for PIR is used a polyester polyol.

Thanks in advance.

K. Listner et. al. have developed a model of

**oxide film growth kinetics**based on the transportation of Anions, Cations and Interstitial Cations across the film. In order to use the model, one should know he value of potential drops in metal/film, film/solution interfaces and also within the film.I am trying to apply this model for the Al/Al2O3/air and Al-1Mg/Al2O3/air systems. The question is were can I find this potential drops? any paper or experimental work?

You can find the model in the attachment and the aforementioned paper here:

If I have to study adsorption kinetics of dye on any porous material, how do I experimentally determine C

_{e}. For exampledye concentration - 100mg/L

adsorbent amount - 10mg

The adsorbent is stirred for 200 min in the dye solution where aliquots are collected at 0,2,5,10,20,50,100,150,200 min respectively.

From thermodynamics and kinetics point of view, why dislocation exist at low temperature and tend to disappear at higher temperature? (e.g. annealing)

Could anybody help understand the following curve? What is the criteria to be satisfied for each curve?

So I am using Biacore T200 and want to perform a kinetics analysis on a small molecule that is bound to my protein of interest. My question is what parameters should I use, for example contact/dissemination time and flow rate. I have a problem as my results show two different curve sets, one at around 200s and another at around 900s. The 900s seems to be the correct one. What is going on?

I'm using linear form equation for isotherm, kinetic and breakthrough model for adsorption. Instead of using R2 to find the best fit, i wanna calculate error using ARE,Chi square,thus is it possible?or is there any error analysis i can use for linear form equation.Thanks for your kind helps.

For my adsorption system I need to calculate thermodynamic parameters. For the study I used 3 equations

1. ∆G = −RT lnb (b is the Langmuir isotherm constant)

2. ∆G = ∆H −T∆S

3. ln b=- (∆H/RT)+(∆S/R)

When I plot the graph of ln b Vs 1/T. I got a positive gradient and a negative intercept. Giving a negative ∆H, ∆G, and negative ∆S.

Is it possible to have such values and a graph and is the graph acceptable with a positive gradient?.

Hi,

When glass fibers are coated, a coupling agent such as gamma-APS is applied to the surface, and is reacted with silica surface resulting in the formation of [Glass]-Si-O-Si-[Coupling Agent] covalent bonds.

When these coated glass fibers are exposed to water environment, then these bonds are known to be cut by the action of hydrolysis (reversible reaction).

**My questions are**: (1) what is the rate of this hydrolysis reaction, resulting in broken bonds between glass and coupling agents, any literature available? (2) Are there any existing models that can describe the kinetics of this reaction, and if yes which ones?

Thank you very much!

Best Regards,

Andrey

Isotopic fractionation of water isotopologues during phase changes (liquid-vapor) are well known and I am wondering if there is a kinetic fractionation possible in liquid water, for example, when water is flowing in a long tube (10m) of small diameter (1/4 inch) and passing through a particulate filter?

Thanks.

Dear all,

I am in search of such an equation or model which can be used to express relative growth rate or growth kinetics of mushroom.

Your valuable suggestion will be highly appreciated.

Regards

Vinod Kumar

Hello all,

I would like to get a curing kinetics of a resin at a certain temperature. I have seen many papers, but what I fail to understand is, if the measurement is a single shot (i.e. single measurement) or for each temporal (time) point, do I have to do one measurement (I know the 100% curing reaction that has to be done for reference).

If the answer is yes (i.e. a single shot measurmeent), what do i actually measure as a function of time (simply heat flow?).

Thanks for helping.

Best regards

Santhosh

The protein I am interested in have transmembrane region as well as a soluble region. I am more interested in how the soluble region comes together for function. Would appreciate if anyone can provide suggestions on what methods to use?

What are the key points which I should know before applying any kinetic model equation in my experimental data?

What are the basic requirements, advantages and limitations of first, pseudo-first, second or third order equations to apply on kinetic studies of any experimental data?

Does R square value decides that which equation will be fitted into data?

I am working on myco-remediation of heavy metals by using mushrooms and I want to demonstrate the metal removal during the growth phase of mushrooms, because certain mushroom species actively captures metal ions from their contaminated substrate.

My question is that can I use BET theory to validate and present my experimental data?

If yes?

Then please could anyone tell me what are the steps to follow?

If No?

Then, why? and Which possible and exact model can work in my case?

The mechanism of removal is given in the attached image.

Thank you !

Often enzymes and artificial enzymes are defined as those molecules that show saturation kinetics. What is the alternative to this behaviour ? Would say an organometallic catalyst not show a saturation curve too? Can we apply the michaelis menten model to non enzyme catalysts?

Thanks!!

Dear all,

Does anyone has an idea or refer me to a paper where I can find out how to link experimental kinetic rate with FES obtained from Metadynamics.

Regards,

I am intereseted about a software for the thermoluminescence glow curves deconvolution (with general order kinetics)...Can someone tell me where can I find it, free or not?

Hi all,

Can you help me with this question: the information is as follows.

Enzymes such as acetylcholinesterase and uridine kinase show the phenomenon of substrate inhibition. The kinetics of substrate inhibition can be described by a modified Michaelis-Menten kinetics.

v=Vmax.S/(K

_{M}+S)(1 +S/K_{I})Determine the concentration of S,where the reaction rate reaches a maximum. This maximum rate should not be confused with Vmax, which is not reached in the case of substrate inhibition.

Hi all,

Consider a reaction that proceeds autocatalytically with the kinetics v=k*a*b. At which concentrations of A reaction will be fastest? Also what will be the concentration of B?

Assumption is, sum of A and B is constant.

Thanks

I need to find the kinetics for the oxidation of hmf to fdca, in the presence of water/acetic acid solvent. Intermediates such as DFF and FFCA are produced during the process, can I find any kinetics for such reactions too?

when the reaction stabilizes.

I'm working on Ls-Dyna in impact simulations of projectile & target.

How to measure

**Kinetic energy**of projectile? (what parameters do I need to define in pre-post?)Also how to calculate

**residual velocity**of projectile?During simulation elements of target are getting deleted on failure, so it is affecting overall mass of the system. how do I conserve mass of the system?

I am trying to predict the balance between the kinetics involved in lubricating oil surface oxidation and degradation. I have found bits and pieces on the kinetics for initiation, propagation, and termination for some polymers, but a comprehensive set of reactions for any lubricating oil would be very helpful.

I am just curious if is possible to relate or derive the Koff (or eventually Kd) of ligand-receptor complex on the basis of the residence time observed in the binding site during Molecular dynamics simulations.

I have a series of weak binders and I would like to do some MD simulations in order to evaluate the residence time in the binding site during MD. So, I wonder if I could use some unbiased or enhanced MD methods to derive Koff or Kd from the residence time of each compound.

Hello everyone.

For my master thesis I want to make some thermos-chemical analysis of a prepreg. Therefore I need the kinetic parameters of the curing reaction. For my thesis I decided to use a model free/ isoconversional method. So far I was able to calculate the dependence of activation energy on the extent of conversion.

Now to my question. For a model free analysis do I need the pre-exponential factor and the reaction model to get the rate of the kinetic process (this d alpha/ d t)? I tried to calculate the pre-exponential factor with the use of the compensation effect but the results are looking wrong.

At the end the goal is to couple the heat equation with this rate term (heat equation with internal generation).

I would be very thankful for any suggestions.

FESEM image of a membrane sample containing fillers, like nano-silica is present there, which have to be explained from thermodynamic and kinetic point of view.

While studying the effect of residence time on reactants conversion to product, it was noticed that after some time the conversion is no longer increasing, but remain almost stable. Generally, it is known that reaction rate decrease with time, but this may not be a sufficient reason for the observed trend. Kinetically/mass transfer limited phenomenon may not also apply here considering that the reaction is kinetically limited in the initial stage, so in theory it can not change to mass transfer later on. A possible reason but not sure about is that the reaction order or mechanism could change after sometime.

How can we calculate KH/KD for kinetic studies??

How can I quantify an enzymatic kinetics that converts ATP to AMP? What techniques besides HPLC can I use? Thank.

Hi, I have the next problem with a project that I am just starting.

One of the methods used to quantify ampicillin uses a CuSO4 buffer. The problem is that when heating the ampicillin in the presence of this compound occurs a reaction which is important to do the kinetic study.

The objective then, is to design an experiment that studies this reaction from the kinetic point of view.

I have been checking for some information but I have not being able found anything useful yet! thanks!

I use as reagent for my reaction Suzuki (1-Iodo-4-nitrobenzene and 4-tolylboronic acid) so my sample is analyzed with GC

Why the first order kinetics used in polyphenol degradation, despite the fact that in some cases the decrease of concentration is linear?

For kinetics, can amylose or amylopectin be used?

Why maltopentaose is used? Why not starch?

Seen some papers which mention Km and Ki values using maltopentaose as substrate. Why?

Hi

I would like to know if anyone knows how to calculate pancreatic lipase inhibition. From the papers I saw, the calculation was done based on this formula

ABc-ABs divided by ABc and multiply by 100, where ABc is the absorbance of the control and ABs is the absorbance of the samples. This method did not work for me because it gave me a negative result.

For my own calculation, I first find the log of the absorbance of both control and samples before using the formula I mentioned above. I just want to be sure if what I did was right or wrong. Please I need more explanation on this.

I would also like to know if anyone can give me the method for the kinetics of enzyme inhibition for pancreatic lipase. I did it but all my values are negatives even at lower substrate concentration. I don't know if I am doing something wrong.

Thank you.

Hi,

Could you recommend me a mathematical expression to describe kinetic in UASB reactor?

I need that the expression includes the pH and/or Temperature.

I want to use the Axial Dispersion Model including the reaction term as a function of pH and/or Temperature

Regards,

How does the temperature of metal hydride influence the reaction rate?

Usually the degradation rate of Rhodamine B follows pseudo first order kinetics. But there is few reported literature zero order kinetics was mentioned. Is it right to follow zero order kinetics ? If it is possible in which circumstances it is true ?

i want to do an in vitro drug kinetic assay using nano particle and liposome as a carrier

I need a method to solve the EDP who describe the kinetics of transesterification reaction