Transient temperature jump studies

TAS = 0) obtained with the 5 10°C temperature shift and the proportionally small optical changes in UV-Visible spectroscopy associated with the transient disequilibrium state. However, these limitations do not seem to apply to protein folding studies in which changes of tryptophan fluorescence or that of the fluorescently labeled proteins were monitored. In addition to a temperature jump, protein unfolding can also be rapidly initiated by a pressure jump. The dead time of the recently developed pressure-jump instrument is 50 ts for a pressure jump of 100 bar. ... 

A number of soil chemical phenomena are characterized by rapid reaction rates that occur on millisecond and microsecond time scales. Batch and flow techniques cannot be used to measure such reaction rates. Moreover, kinetic studies that are conducted using these methods yield apparent rate coefficients and apparent rate laws since mass transfer and transport processes usually predominate. Relaxation methods enable one to measure reaction rates on millisecond and microsecond time scales and 10 determine mechanistic rate laws. In this chapter, theoretical aspects of chemical relaxation are presented. Transient relaxation methods such as temperature-jump, pressure-jump, concentration-jump, and electric field pulse techniques will be discussed and their application to the study of cation and anion adsorption/desorption phenomena, ion-exchange processes, and hydrolysis and complexation reactions will he covered. 

The objective of this chapter is to discuss the theory of chemical relaxation and its application to the study of soil chemical reaction rates. Transient relaxation techniques including temperature-jump (t-jump), pressure-jump (p-jump), concentration-jump (c-jump) and electric-field pulse will be discussed both as to their theoretical basis and experimental design and application. Application of these techniques to the study of several soil chemical phenomena will be discussed including anion and cation adsorp-tion/desorption reactions, ion-exchange processes, hydrolysis of soil minerals, and complexation reactions. 

The stopped-flow rapid-mixing and temperature-jump kinetic studies from the author s laboratory (72,89) which describe the reaction of the enzyme-NADH complex with the intense chromophore, direct evidence for the involvement of zinc ion as a Lewis acid in the activation of the aldehyde carbonyl for reduction. These studies show that reduction of DACA involves the formation of a transient chemical intermediate (Amax 464 nm, emax 6.2 X 10 M-icm i) in the neutral pH range. At pH values above 9 and in the presence of high enzyme concentrations, the transient species observed... 

Transient 2D-IRS has been used to study the dynamics of reversible and irreversible processes that are initiated by an external force typical investigations have included temperature jump (T-jump) [102] and flash photolysis experiments... 

So far, all of the studies detailed have dealt primarily with nonequilibrium states, i.e micelle formation or breakdown stimulated by an external trigger, e.g., a jump in pressure, temperature, or concentration. It has of course been shown, however, that even at equilibrium, micelles are by their nature transient species with millisecond-scale lifetimes, and that dynamic processes exchange surfactant molecules between aggregates, interfaces, and bulk solutions. Studies of the kinetics of these processes in equilibrium solutions are much more scarce, mainly owing to experimental difficulties. 

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