LOW TEMPERATURE CHEMISTRY/KINETICS/PHOTOAFFINITY LABELS

在当前的授权期内发现 简单芳香族助剂的光化学非常敏感 为了温度。苯基叠氮化物的室温光解 产生脱氢氮卓类药物，这种药物相对不具反应性，容易 聚合形成焦油。然而，苯叠氮化合物的光解 在77K下的刚性基质(RH)中产生三线态苯基尼龙，该苯基尼龙 在这个温度下，黑暗中是无限稳定的。然而， 三重态氮的光解导致氢原子的抽离 从基质(RH)形成自由基对，当加热到 100K后，自由基对坍塌形成偶联产物。 77K下的光化学步骤序列有效地导致了 联轴器产品等产量较高。我们利用了这一点 通过对光化学和低温EPR光谱的研究 在77K时，经修饰的胰凝乳酶。在这个提案中，实验 概述了将低温方法扩展到其他方法的情况 以及引入新的非共价结合的光探针的酶 预计在77K时特别有效的试剂。

During the current grant period have discovered that the photochemistry of simple aromatic aides are remarkably sensitive to temperature. Photolysis of phenyl azide at room temperature produces dehydroazepine which is relatively unreactive and prone to polymerization to form tar. However, photolysis of phenyl azide in a rigid matrix (RH) at 77K produces triplet phenyl nitrene which at this temperature is indefinitely stable in the dark. However, photolysis of triplet nitrenes results in hydrogen atom abstraction from the matrix (RH) to form radical pair, which when warmed to 100K followed by radical pair collapses to form coupling product. The sequences of photochemical steps at 77K efficiently leads to coupling products such as in high yields. We have exploited this by studying the photochemistry and low temperature EPR spectroscopy of modified chymotrypsins at 77K. In this proposal experiments are outlined which extend the low temperature method to other enzymes and which introduce new non covalently bound photoprobe reagents which are expected to be particularly eficient at 77K.