血卟啉与左旋多巴相互作用的研究

Studies on the Interaction of Hemoporphyrin Metalporphyrin and Levo Dopa

文章采用荧光光谱法研究了卟啉类化合物血卟啉与左旋多巴之间的相互作用,研究发现:在模拟人体生理条件下(pH 7.4),随着体系中血卟啉浓度的增大,左旋多巴的荧光强度逐渐猝灭,荧光发射峰发生轻微蓝移,并有等发射点出现,表明卟啉与左旋多巴发生了作用,且形成了新的配合物。根据Stern-Volmer方程,求得了不同温度时两者的结合常数、相关系数及热力学常数,实验结果表明血卟啉HP对左旋多巴荧光猝灭速率常数Kq值均大于2.0×1010L.mol-1.s-1,证实了血卟啉与左旋多巴的结合反应为静态猝灭反应,且随着温度的升高,结合反应常数有不同程度的减小。在25℃时,ΔG=-26.58 kJ.mol-1;ΔS=138.7 J.K-1;ΔH=14.71 kJ.mol-1。

Levo dopa （L-DOPA） is a prodrug that is converted to dopamine by DOPA decarboxylase and can cross the blood- brain barrier. When in the brain, levo dopa is decarboxylated to dopamine and stimulates the dopaminergic receptors, thereby compensating for the depleted supply of endogenous dopamine seen in Parkinson＇s disease. So, Levodopa is a medication used to treat Parkinson＇s disease clinically. In the present paper the interaction of hematoporphyrin and levo dopa was studied by fluorescence at different temperature in the quenching experiments. The excitation fluorescence spectrum of levo dopa displayed a peak at 282 nm and that for the emission fluorescence spectrum was at 320 nm in pH 7.4 buffer solution. The intensity of the fluorescence was effectively quenched as the hemoporphyrin concentration increased and the emission spectra blue-shifted with the isos- bestic point appearing, indicating that the interaction between hematoporphyrin and levo dopa occurred and a new complex was formed. According to Stern-Volmer equation and Lineweaver-Burk double-reciprocal equation, the thermodynamic parameters, formation constants and some other concerned constants were obtained. The quenching rate constants Kq bigger than 2.0×10^10L·mol^-1·s^-1 were found. So the kinetic behavior of the reaction between hematoporphyrin and levo dopa was suggested to be static fluorescence quenching model. In addition, with the temperature increasing, the formation constants decreased to some extent.At 25℃ ΔG=-26.58 kJ.mo^l-1;ΔS=138.7 J·K^-1;ΔH=14.71 kJ·mol^-1.