Temperature-jump relaxation kinetic

Temperature-jump relaxation kinetics of the P-450(,a spin equilibrium have been measured. 

The formation of a one host-two guests inclusion-complex could proceed by way of two main mechanisms (/) dimerization of the guest, followed by inclusion and (2) stepwise inclusion of two guest molecules. In order to distinguish between these two possibilities, several temperature-jump relaxation kinetic studies have been carried us-... 

Perkin Elmer MPF-3 spectrofluorometer. X- and Q-band measurements of EPR spectra were carried out at liquid nitrogen and liquid helium temperatures. Microcalorimetric measurements were performed on a LKB 10700 batch microcalorimeter. Temperature-jump relaxation kinetics were measured using a double beam instrument (18) with a cell adapted for anaerobic work. The relaxation signals were fed into an H.P. 2100 computer and analyzed as described in Ref. 7. The pulse radiolysis exepriments were carried out on the 5-MeV linear accelerator at the Hebrew University. Details of the system have been published previously (19). 

Narasimhulu, S., and Willcox, J. K. (2001) Temperature-jump relaxation kinetics of substrate-induced spin-state transition in cytochrome P450 (Comparison of the wild-type and C334A mutant P450CAM and P4502B4), Arch. Bioch. and Bioph. 388, 198-206. 

A large programme utilizing temperature-jump relaxation methods for the study of tautomerism in aqueous solution has led the Dubois group to determine the kinetic and thermodynamic parameters of the equilibrium (130a) (130b) (78T2259). The tautomeric... 

DR. THOMAS The kinetic parameters of micelles are very well known, having been determined by temperature-jump relaxation methods and various other techniques. There are several kinetic events which can be described. First of all, the fastest event is the exchange of the counter ion (e.g., the sodium counter ion, in sodium lauryl sulfate). These ions exchange... 

Kao and Tsien studied the Ca +-binding kinetics of fura-2 and azo-1 by temperature-jump relaxation methods. In 140 mM KCl at 20°C, the respective association and dissociation rate constants for fura-2 were 6x10 M s and 97 s these kinetic properties were insensitive to hydrogen ion concentration over the pH range from 7.4 to 8.4. Azo-1 was studied in 140 mM KCl At 10°C, azo-... 

Studies on the kinetic behaviour of nucleoside and nucleotide complexes are less common than those on structural aspects. This arises because of the rapid rates of the formation and dissociation reactions, requiring NMR or temperature-jump relaxation measurements. The number of species that can coexist in solution also hinders interpretation. The earlier kinetic studies have been reviewed by Frey and Stuehr.127 Two important biological reactions of the nucleotides are phosphoryl and nucleotidyl group transfers. Both reactions are catalytic nucleophilic reactions and they both require the presence of a divalent metal ion, in particular Mg2+. Consequently, one of the main interests has been in understanding the catalytic mechanism of the metal ion involvement. This has mainly involved studies on related non-enzymic reactions.128... 

Temperature-jump relaxation and the stopped-flow methods are suitable to follow the concentration changes over extremely short time intervals. Such studies have indicated that immune reaction kinetics resemble other biological systems in which ligands are bound to proteins (Weber, 1975) in that the binding strength of small molecules is largely dictated by the constant. The association rate constants ka, are very similar for various antibody-antigen systems, i.e., for... 

Further support for the existence in solution of near equal amounts of the 7H and 9H protomers of purine is provided by carbon-13 resonance data in which the disposition of the acidic proton can be correlated with the magnitude of the shift changes of the C-4 and C-5 bridgehead atoms. Use of the 7- and 9- methyl homologs as reference compounds and extrapolation of the results to the 7H and 9H purines by applying a- and j -substituent parameter corrections gives 40% for the 7H tautomer in dimethyl sulfoxide and an estimate of 58% in water. " Data obtained from a temperature-jump relaxation technique used to study the rapid kinetics of 7H 9H prototropy of adenine in aqueous solution has given values for the equilibrium constant K = C7H/C9H = 0.28 at 20°) and the 7H isomer population ( 22%). This... 

Activation parameters are more and more frequently being reported as important features of temperature jump relaxation method kinetic studies. This is true in spite of the fact that the restricted temperature range accessible to a Joule heating temperature jump apparatus and the usual 10% uncertainties in measured relaxation times are not favorable characteristics for achieving precise values of AH and AS. ... 

Nickel(II) is one of the least reactive of the labile metal ions and the most amenable as regards kinetic investigation. Indeed, more than a hundred complex formations have been studied. Although some complexes require fast reaction techniques like temperature-jump relaxation, many systems have been studied adequately by more normal flow methods. The mechanisms of ligand replacement in Ni(II) complexes have been reviewed a number of times, notably by Wilkins [77]. 

Kao, J. P. Y. Tsien, R. Y. (1987). Ca binding kinetics of fura-2 and azo-1 from temperature jump relaxation measurements. Biophysical Journal, 53, 635-9. 

Of particular interest is the use of uv-visible spectrophotometry, since there is the added possibility of following the kinetics of simple hydrogen-bond formation by means of the temperature-jump relaxation technique with a conventional optical detection system. The method is suitable for acid or base species which contain a suitable chromophore, for example 2,4-dinitrophenol (2,4-DNP),... 

The kinetics of micellization of perfluorinated surfactants has been investigated by Hoffmann and co-workers [74-80] by pressure jump and a shock wave method with conductivity detection [74-80]. Hoffmann and Ulbricht [75] also used a temperature jump relaxation technique [81] with optical detection, utilizing a pH indicator (thymol blue) to observe relaxation processes of a 1 1 mixture of perfluorooctanoic acid and its sodium salt. For micellar systems in which fast relaxation times could be measured, the parameters k /n, k lcr, a ln, and k /n were calculated. 

Perturbation or relaxation techniques are applied to chemical reaction systems with a well-defined equilibrium. An instantaneous change of one or several state fiinctions causes the system to relax into its new equilibrium [29]. In gas-phase kmetics, the perturbations typically exploit the temperature (r-jump) and pressure (P-jump) dependence of chemical equilibria [6]. The relaxation kinetics are monitored by spectroscopic methods. 

The first experimental data for a reaction involving proton transfer from a hydrogen-bonded acid to a series of bases which were chosen to give ApK-values each side of ApK=0 are given in Fig. 15 (Hibbert and Awwal, 1976, 1978 Hibbert, 1981). The results were obtained for proton transfer from 4-(3-nitrophenylazo)salicylate ion to a series of tertiary aliphatic amines in aqueous solution, as in (64) with R = 3-nitrophenylazo. Kinetic measurements were made using the temperature-jump technique with spectrophoto-metric detection to follow reactions with half-lives down to 5 x 10"6s. The reciprocal relaxation time (t ), which is the time constant of the exponential... 

The most common methodology for measuring fast kinetics in real time is to perturb a system at equilibrium for a time duration that is much shorter than the relaxation kinetics that follow perturbation. This perturbation can be achieved by changing the concentration of chemicals through fast mixing (stopped-flow), changing the temperature of the solution (temperature jump), simultaneously changing the... 

The complexity of the binding dynamics of 1 with DNA became apparent in subsequent temperature jump experiments, where three relaxation processes were observed.112 The fastest relaxation process had a small amplitude (< 14%) and its kinetics were uncoupled from the second and third relaxation processes. This fast process was assigned to the binding of 1 to a minor site with a k+ value of 1.5x10 M s and a value of 6.9 x 10 s. This assignment was problematic because of the possible interference of artifacts for temperature jump experiments when the fluorescence detection is not performed at the magic angle,29 and this kinetic component was not observed in later studies.94,120... 

Temperature jump studies on the binding dynamics of 5 with ct-DNA and T2 Bacteriophage DNA showed two lifetimes in the relaxation kinetics.117 The observed... 

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