Comparative kinetic analysis

The subunit structure of PH, an ot4P4y484 (SDS-PAGE and gel permeation chromatography), is similar to that of the NAH (Gladyshev et al. 1994a). Comparative kinetic analysis of PH and XDH from C puri-... 

Kronzucker HJ, Glass ADM, Siddiqi MY, Kirk GJD. 2000. Comparative kinetic analysis of ammonium and nitrate acquisition by tropical lowland rice implications for rice cultivation and yield potential. New Phytologist 145 471-476. 

A comparative kinetic analysis of the rate of guanidinylation of benzylamine with 1,3-bis(benzyloxycarbonyl)- or l,3-bis(teri-butoxycarbonyl)-2-triflylguanidinet with the rates of those reagents discussed in Sections 2.6.1.6.1 and 2.6.1.6.2 clearly indicated that the triflyl derivatives are the most powerful reagents (Figure l),f l well-suited for guanidinylation of simple amino acid derivatives as well as of peptides in solution or linked to resins.In the latter case, a selective protection of the A -amino group of the ornithine residues is required. 

A comparative kinetic analysis of IRPl activation by NO and H2O2 in culture cells yielded the unexpected outcome that NO, unlike H2O2, elicits a slow activation of IRPl which, in kinetic terms rather resembles responses to iron starvation [136], Furthermore, iron starvation and NO result in a slow induction of both IRPl and IRP2, while H2O2 exclusively activates IRPl with rapid kinetics [126, 136]. IRPl induction by H2O2 is biphasic, in contrast to the effects of iron starvation and NO. While the iron chelator desferrioxamine and NO need to be continuously present for IRPl activation, the presence of H2O2 (at a minimal threshold eoncentration of 10 pm) is only required for 10-15 minutes, and then the activation of IRPl can be completed in the absence of the effector [136, 142]. 

Vereshchagin AG. Comparative kinetic analysis of oil accumulation in maturing seeds. Plant Physiol Biochem 1991 29 385-93. 

In contrast to SDS, CTAB and C12E7, CufDSjz micelles catalyse the Diels-Alder reaction between 1 and 2 with enzyme-like efficiency, leading to rate enhancements up to 1.8-10 compared to the reaction in acetonitrile. This results primarily from the essentially complete complexation off to the copper ions at the micellar surface. Comparison of the partition coefficients of 2 over the water phase and the micellar pseudophase, as derived from kinetic analysis using the pseudophase model, reveals a higher affinity of 2 for Cu(DS)2 than for SDS and CTAB. The inhibitory effect resulting from spatial separation of la-g and 2 is likely to be at least less pronoimced for Cu(DS)2 than for the other surfactants. 

For counterions that can form esters with the growing oxonium ions, the kinetics of propagation are dominated by the rate of propagation of the macroions. For any given counterion, the proportion of macroions compared to macroesters varies with the solvent—monomer mixture and must be deterrnined independentiy before a kinetic analysis can be made. The macroesters can be considered to be in a state of temporary termination. When the proportion of macroions is known and initiation is sufftcientiy fast, equation 2 is satisfied. 

A detailed study of the solvolysis of L has suggested the following mechanism, with the reactivity of the intermediate M being comparable to that of L. Evidence for the existence of steps ki and k 2 was obtained fiom isotopic scrambling in the sulfonate M when it was separately solvolyzed and by detailed kinetic analysis. Derive a rate expression which correctly describes the non-first-order kinetics for the solvolysis of L. 

The initial goal of the kinetic analysis is to express k as a function of [H ], pH-independent rate constants, and appropriate acid-base dissociation constants. Then numerical estimates of these constants are obtained. The theoretical pH-rate profile can now be calculated and compared with the experimental curve. A quantitative agreement indicates that the proposed rate equation is consistent with experiment. It is advisable to use other information (such as independently measured dissociation constants) to support the kinetic analysis. 

Although it would appear that plots of ln[—ln(l — a)] against ln(f — t0) provide the most direct method for the determination of n from experimental a—time data, in practice this approach is notoriously insensitive and errors in t0 exert an important control over the apparent magnitude of n. An alternative possibility is to compare linearity of plots of [—ln(l — a)]1/n against t this has been successful in the kinetic analysis of the decomposition of ammonium perchlorate [268]. Another possibility is through the use of the differential form of eqn. (6)... 

References to a number of other kinetic studies of the decomposition of Ni(HC02)2 have been given [375]. Erofe evet al. [1026] observed that doping altered the rate of reaction of this solid and, from conductivity data, concluded that the initial step involves electron transfer (HCOO- - HCOO +e-). Fox et al. [118], using particles of homogeneous size, showed that both the reaction rate and the shape of a time curves were sensitive to the mean particle diameter. However, since the reported measurements refer to reactions at different temperatures, it is at least possible that some part of the effects described could be temperature effects. Decomposition of nickel formate in oxygen [60] yielded NiO and C02 only the shapes of the a—time curves were comparable in some respects with those for reaction in vacuum and E = 160 15 kJ mole-1. Criado et al. [1031] used the Prout—Tompkins equation [eqn. (9)] in a non-isothermal kinetic analysis of nickel formate decomposition and obtained E = 100 4 kJ mole-1. 

As the reaction proceeds higher sulfanes and finally Ss are formed. The reaction is autocatalytic which makes any kinetic analysis difficult. The authors discussed a number of reaction mechanisms which are, however, obsolete by today s standards. Also, the reported Arrhenius activation energy of 107 17 kJ mol is questionable since it was derived from the study of the decomposition of a mixture of disulfane and higher sulfanes. Nevertheless, the observed autocatalytic behavior may be explained by the easier ho-molytic SS bond dissociation of the higher sulfanes formed as intermediate products compared to the SS bond of disulfane (see above). The free radicals formed may then attack the disulfane molecule with formation of H2S on the one hand and higher and higher sulfanes on the other hand from which eventually an Ss molecule is split off. 

Compare the pros and cons of kinetic analysis by fitting a Langmuir-Hin-shelwood model to measured data and by microkinetic analysis. 

A consistent picture for dynamics of heterogeneous ET has been emerging in the last 5 years with the development of new experimental approaches. Techniques such as AC impedance, modulated and time-resolved spectroscopy, SECM, and photoelectrochemical methods have extended our knowledge of charge-transfer kinetics to a wide range of time scales. This can be exemplified by comparing impedance analysis, which is limited to k of... 

Although there are other ways, one of the most convenient and rapid ways to measure AH is by differential scanning calorimetry. When the temperature is reached at which a phase transition occurs, heat is absorbed, so more heat must flow to the sample in order to keep the temperature equal to that of the reference. This produces a peak in the endothermic direction. If the transition is readily reversible, cooling the sample will result in heat being liberated as the sample is transformed into the original phase, and a peak in the exothermic direction will be observed. The area of the peak is proportional to the enthalpy change for transformation of the sample into the new phase. Before the sample is completely transformed into the new phase, the fraction transformed at a specific temperature can be determined by comparing the partial peak area up to that temperature to the total area. That fraction, a, determined as a function of temperature can be used as the variable for kinetic analysis of the transformation. 

Comparing different polyethylenimines (Table III), we observe that the deacylation rate with the lauryl polymer is approximately equal to that for unmodified polymer. Kinetic analysis reveals that the binding of substrate by the respective polymers, as measured by vKd, is not appreciably different, nor is the rate constant k2. With this substrate, then, there is no evidence that added lauryl groups on the polymer increase the effectiveness of the polymer. 

S.S. Cherry et al, Identification of Important Chemical Reactions in Liquid Propellant Rocket Engines , Pyrodynamics 6 (3—4), 275—96 (1969) CA 70,. 98394 (1969) [The authors state that the kinetics of nonequilibrium expansion of the propint system N204/A-50 (UDMH 49 plus hydrazine 51 wt%) can be described by the following gas phase reactions with an accuracy such that not more than 0.5 lb force-sec/lb mass variation in specific impulse (at a nozzle expansion rate of 40) is produced, as compared to the results of a full kinetic analysis ... 

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