Schmidt H, Rosenkranz P
Z Naturforsch C Biosci. 1976 Jan-Feb;31(1-2):29-39. doi: 10.1515/znc-1976-1-209.
The kinetics of the photodynamic desactivation of lysozyme in presence of acridine orange as the sensitizer have been investigated in detail varying oxygen, protein, dye concentration, ionic strength and pH value. The kinetics can be approximately described as an over all pseudo-first-order rate process. Changing the solvent from water to D2O or by quenching experiments in presence of azide ions it could be shown that the desactivation of lysozyme is caused exclusively by singlet oxygen. The excited oxygen occurs via the triplet state of the dye with a rate constant considerably lower than that to be expected for a diffusionally controlled reaction. Singlet oxygen react chemically (desactivation, k=2.9 X 10(7) m(-1) sec(-1)) and physically (quenching process, k=4.1 X 10(8) m(-1) sec(-1)) with the enzyme. The kinetical analysis shows that additional chemical reaction between singlet oxygen and lysozyme would have only little influence on the kinetics of the desactivation as long as their products would be enzymatically active and their kinetical constants would be less than about 1 X 10(8) m(-1) sec(-1)).
在存在吖啶橙作为敏化剂的情况下，研究了溶菌酶光动力失活的动力学，详细改变了氧气、蛋白质、染料浓度、离子强度和pH值。该动力学可以近似地描述为一个整体的准一级速率过程。将溶剂从水改为重水，或在叠氮离子存在下进行猝灭实验，结果表明溶菌酶的失活完全是由单线态氧引起的。激发态氧通过染料的三重态产生，其速率常数远低于扩散控制反应预期的值。单线态氧与酶发生化学反应（失活，k = 2.9×10⁷ m⁻¹ s⁻¹）和物理反应（猝灭过程，k = 4.1×10⁸ m⁻¹ s⁻¹）。动力学分析表明，只要单线态氧与溶菌酶反应的产物具有酶活性且其动力学常数小于约1×10⁸ m⁻¹ s⁻¹，那么单线态氧与溶菌酶之间的额外化学反应对失活动力学的影响就很小。
