Article

An experimental methodology for measuring volume changes in proton transfer reactions in aqueous solutions

Department of Chemistry and Biochemistry, Eastern Washington University, Чини, Washington, United States
Biophysical Chemistry (Impact Factor: 2.32). 08/1998; 73(1-2):13-22. DOI: 10.1016/S0301-4622(98)00108-2
Source: PubMed

ABSTRACT A fast perturbation in proton concentration can be induced in aqueous solution using a pulsed ultraviolet laser and suitable photolabile compounds which, upon photoexcitation, irreversibly release protons. The volume change and the rate constant for the reaction of the photodetached protons with proton-accepting groups in solution can be monitored using time resolved photoacoustics. A typical proton concentration jump of 1 microM can be obtained with a 200-microJ laser pulse at 308 nm. Reaction dynamics from 20 ns to 5 micros can be easily followed. The methodology we establish represents a direct, time-resolved measurement of the reaction volume in proton transfer processes and an extension to the nanosecond-microsecond range of traditional relaxation techniques, such as stopped-flow. We report example applications to reactions involving simple molecules and polypeptides.

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