LOW TEMPERATURE CHEMISTRY/KINETICS/PHOTOAFFINITY LABELS

在目前的赠款期间，发现， 简单芳香族助剂的光化学反应非常敏感， 温度。 叠氮苯的室温光解 产生脱氢吖庚因，其相对不反应， 聚合形成焦油。 然而，苯基叠氮的光解 在刚性基体（RH）中，在77K下产生三重苯基氮宾， 在这个温度下在黑暗中是无限稳定的。 然而，在这方面， 三重态氮烯的光解导致氢原子的夺取 从基质（RH）中形成自由基对，当加热时， 100K，随后自由基对塌缩形成偶联产物。 在77K下的光化学步骤的顺序有效地导致 例如以高产率偶联产物。 我们利用了这一点 通过研究光化学和低温EPR光谱， 修饰的胰凝乳蛋白酶在77K。 在这个实验中， 将低温法推广到其它方法， 引入新的非共价结合的光探针 预计在77K下特别有效的试剂。

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.