Photolyses of mammalian oxy-hemoglobin studied by nanosecond photoacoustic calorimetry

Enthalpy and conformational volume changes in photolyses of oxy-hemoglobin (HbO2) of human, bovine, pig, horse and rabbit are investigated by photoacoustic calorimetry. In the experiment, a pulsed Nd:YAG laser is used as an exciting source, and a PVDF film transducer and a PZT transducer are used to detect the photoacoustic signals. Based on the time scales of the excitation and detection systems as well as the photolysis processes of HbO2, it can be indicated that the measured enthalpy and conformational volume changes are related to slow geminate recombination and tertiary relaxation in photolyses of HbO2, which are with the time scale of 30–40 ns and 100–150 ns, respectively. The results show that the enthalpy and conformational volume changes are different for both photolysis processes of HbO2 and also for various mammals. The different results among the five mammals are analyzed and discussed briefly.