灌注蛙视网膜中视紫红质漂白过程中慢热反应的动力学

Slow thermal reactions occurring in the rhodopsin rods of flash-irradiated frog retinas were investigated spectrophotometrically.2. Five substances were identified as reactants: metarhodopsin II, metarhodopsin III, all-trans-retinal, opsin, and all-trans-retinol.3. Quantitative analysis showed that the transition between these substances are not a series of three consecutive reactions.4. An alternative scheme, compatible with the results, consisted of four reactions and involved two parallel pathways for the decay of metarhodopsin II, viz. conversion into metarhodopsin III, and hydrolysis into retinal and opsin.5. The first-order rate constants for the four reactions were as follows: 1.4 x 10(-2) sec(-1) for the conversion of metarhodopsin II into metarhodopsin III; 7.9 x 10(-3) sec(-1) for the hydrolysis of metarhodopsin II; 1.4 x 10(-3) sec(-1) for the hydrolysis of metarhodopsin III; and 2.6 x 10(-3) sec(-1) for the reduction of retinal into retinol (21 degrees C).6. Two other four-parameter schemes involving an equilibrium between metarhodopsin II and metarhodopsin III were also considered. One was found to be incompatible with the results. The other, though adequate, did not describe the data as well as the model summarized in 4 and 5. It also had the peculiar property of requiring that two apparently independent parameters be equated.

用分光光度法研究了闪光照射青蛙视网膜视紫红质棒中发生的缓慢热反应。
确定了五种物质为反应物：变视紫红质II、变视紫红质III、全反式视黄醛、视蛋白和全反式视黄醇。
定量分析表明，这些物质之间的转变不是一系列连续的三个反应。
一个与结果相符的替代方案由四个反应组成，涉及变视紫红质II衰变的两条平行途径，即转变为变视紫红质III，以及水解为视黄醛和视蛋白。
这四个反应的一级速率常数如下：变视紫红质II转变为变视紫红质III的速率常数为1.4×10⁻²秒⁻¹；变视紫红质II水解的速率常数为7.9×10⁻³秒⁻¹；变视紫红质III水解的速率常数为1.4×10⁻³秒⁻¹；视网膜还原为视黄醇的速率常数为2.6×10⁻³秒⁻¹（21摄氏度）。
还考虑了另外两个涉及变视紫红质II和变视紫红质III之间平衡的四参数方案。发现其中一个与结果不相符。另一个虽然合适，但对数据的描述不如4和5中总结的模型。它还有一个特殊的性质，即要求两个明显独立的参数相等。

Kinetics of slow thermal reactions during the bleaching of rhodopsin in the perfused frog retina.