Temperature-jump relaxation

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... 

The results of a temperature jump relaxation study of the complexation of metal cations by dibenzo-30-crown-10 [14] in methanol led Chock (1972) to propose a two-step mechanism. The first step (9) comprises a rapid equilibrium... 

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... 

K. Murakami, T. Sano and T. Yasunaga, Bull. Chem. Soc. Japan 54, 862 (1981). This is unusual case where there are no temperature-jump relaxations. The interaction of bovine serum albumin with bromophenol blue is accompanied by four relaxations which are attributed to a fast second-order interaction followed by three first-order steps. 

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-... 

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-... 

A number of methods have been used for determining Kg values cation selective electrodes, pH-metric methods, conductimetry, calorimetry, temperature-jump relaxation measurements, membrane conductance measurements, nuclear magnetic resonance, optical rotatory dispersion. The results listed in Tables 7—10 have been obtained by various methods and at different ionic strengths so they may not always be strictly comparable. However, the corrections are probably small and the experimental accuracy is generally the same or very similar within a certain ligand type. 

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... 

Rich et al. (79) have carried out a temperature jump relaxation study of E. coli asparaginase and reported that the finding of multiple relaxation times is qualitatively consistent with the suggested subunit structure. 

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. 

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... 

TL2221). The mechanism of this proton transfer was also investigated using the temperature-jump relaxation technique (77JA4438). 3-Hydroxypyridine tautomer-ism has also been studied by magnetic circular dichroism spectroscopy (80BCJ3069). 

Fig. 14. Oscillogram of a temperature jump relaxation effect of the system containing antamanide, murexide, and Na+ in methanol...

Callendee, R., Dyee, R. B. (2002) Probing protein dynamics using temperature jump relaxation spectroscopy, Curr. Opin. Struct. Biol. 12, 628-633. 

For these reactions, AG° 0. The experimental measurement of cross-reaction rates is generally more straightforward than the measurement of self-exchange rates. Either the reactants are simply mixed together, or a thermodynamically unstable system is generated rapidly (via pulse radiolysis, flash photolysis, or temperature-jump relaxation) to initiate the redox reaction. Absorption spectroscopy has almost always been used to monitor the progress of protein cross reactions. The primary goal of theory, as will become evident, is to provide a relationship between AG° and AG" " for cross reactions. 

Table III. Activation Parameters for the Forward and Reverse Reactions of the Equilibrium HA + OH A + H 0 in O.IM Ionic Strength (Adjusted with NaCIO ) Aqueous Solution from Temperature Jump Relaxation Method Specific Rates Determined at 12 and 25° (Miles et ah )...

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. ... 

E complex have been examined by temperature jump relax-... 

---