Measurement of enthalpy and volume changes in photoinitiated reactions on the ms timescale with a novel pressure cell

Abstract

Time-resolved photoacoustics is an excellent method with which to measure enthalpy and volume changes of photochemical and photobiological reactions. However, it fails at times longer than ∼10 µs. The design principles of a pressure or volume cell covering the time range of 20 µs to several seconds is presented. The sensitivity of the cell has been verified and its application to the photocycle of bacteriorhodopsin is presented. Because of the similar cell structure and data analysis it is now possible to determine enthalpy and volume changes in photo-initiated reactions over the timescale of nanoseconds to seconds with the same solution.