Photoacoustic calorimetric study of the conversion of rhodopsin and isorhodopsin to lumirhodopsin

Abstract

The enthalpy and volume changes for the conversion of rhodopsin and isorhodopsin to lumirhodopsin have been investigated by time-resolved photoacoustic calorimetry. The conversion of rhodopsin to lumirhodopsin is endothermic by 3.9 +/- 5.9 kcal/mol and is accompanied by an increase in volume of 29.1 +/- 0.8 mL/mol. The lumirhodopsins produced from rhodopsin and isorhodopsin are energetically equivalent.