中文摘要：

时间分辨脉冲光声量热法是利用脉冲激光激发化学物质的光解反应，反应中产生的热能将激发声波，声波的振幅和相位即反映光解反应的中间过程．因此时间分辨光声量热技术是研究光致解离动力学信息的十分有效的方法．利用时间分辨光声量热法测量了激光诱导人、牛，猪、马和兔的氧合血红蛋白光解反应的焓变和结构体积变化．实验中采用波长532nm、脉冲宽度8ns的脉冲激光作为激发光源，光声信号由共振频率为1．5MHz的PZT压电换能器接收，所以实验系统的响应时间范围在10^2ns量级。已知在氧合血红蛋白的光解反应中可以检测到4个过程具有4种不同的反应时间，其中三级结构重组在137-470ns左右．考虑实验系统的时间窗口，所测结果应与血红蛋白的三级结构变化相对应．测量结果显示：不同种类的哺乳动物氧合血红蛋白光解反应中，对应三级结构变化的焓变和结构体积变化各不相同．最后对这一结论进行了讨论．

英文摘要：

A pulsed laser was used to excite photolysis reactions of chemical materials and to generate an acoustic pulse with the amplitudes related to the reaction processes, which are the basis of time-resolved photoacoustie calorimetry （PAC）. Therefore, the dynamics of enthalpy and volume changes accompanied with photoinduced ligand dissociation can be studied by PAC. In this paper, the enthalpy and the comformational volume changes induced by laser photo-dissociation reactions of oxy-hemoglobins of mammals, such as human, bovine, pig, horse and rabbit, were investigated by the PAC. In our experiments, a nano-second laser with the wavelength 532 um and pulse width 8 ns was used as an exciting source, and the PAC signals were detected by a PZT transducer with the resonant frequency of 1. 5 MHz, so the response time of the detection system is in a range of 100 ns-1μs. For oxyhemoglobins, there are four photolysis processes with different lifetime ranging from 100 ps to 350μs. Considering the time window of the experimental system, the enthalpy and the conformational volume changes detected should be caused by the tertiary relaxation of the oxy-hemoglobins with the lifetime of 137-470 ns. The obtained enthalpy and conformational volume changes for all measured mammalian oxy-hemoglobins are different from each other. The enthalpy changes are in the range of 46. 8 - 30. 0 kcal/mol, while the volume changes are in the range of 7. 8-2. 3 ml/mol. Finally, a possible explanation of the results is discussed.