流动与非流动测热方式对酶催化反应放热测量的影响

Effects of flowing and non-flowing detection manner on measuring heat changes of enzyme catalytic reaction

采用微量热仪(Micro DSCⅢ)对鸡肝酯酶催化α-乙酸萘酯水解反应进行了流动与非流动测热方式的对比研究。研究显示,流动测热的流速对反应热测量结果有较大影响,当30μL浓度为120mmol/L的α-乙酸萘酯底物以0.22 mL/min的流速流经0.5 g固定化鸡肝酯酶时,催化反应放出的热量为0.033 J,持续放热时间为495 s;而流速为0.18 mL/min与0.35 mL/min时,测得的放热量分别为0.030 J与0.025 J,持续放热时间分别为625 s与365 s。用与流动测热相同酶活单位的鸡肝酯酶液酶进行非流动测热,所得到目的反应热的量为0.035 J,持续放热时间为800 s。与非流动方式测热相比,流动测热方式的测量灵敏度较高,检测出目的放热量所需时间较短,但不能充分检测出生化反应热总热量。

Some experiments about the effects of flowing and non-flowing detection manner on measuring the heat changes of α-naphthyl acetate catalyzed by chicken liver esterase are investigated using calorimeter Micro DSCⅢ. The results show that in flowing measurement manner, the flow rate affect significantly on the calorimetric result. When 30 μL a-naphthyl flowed through 0.5 g immobilized chicken liver esterase at 0.22 mL/min, the aimed reaction heat change is 0. 033 J, and the whole exothermic process lasts 495 s. And at 0. 18 mL/min and 0. 35 mL/min, the aimed reaction heat change is 0. 030 J and 0. 025 J respectively,the whole exothermic processes lasted 625 s and 365 s. On the other hand, the heat change is examined in non-flowing measurement manner using the same quantum of substrate and esterase,and the aimed heat change is 0. 035 J, the whole exothermic process lasts 800 s. It can be deduced that the flowing measurement manner is more sensitive than the non-flowing measurement manner and cost less detecting time; but it can not detect the reaction heat change completely.