CONTINUOUS-WAVE QUANTUM YIELDS OF VARIOUS COBALAMINS ARE INFLUENCED BY COMPETITION BETWEEN GEMINATE RECOMBINATION AND CAGE ESCAPE
CONTINUOUS-WAVE QUANTUM YIELDS OF VARIOUS COBALAMINS ARE INFLUENCED BY COMPETITION BETWEEN GEMINATE RECOMBINATION AND CAGE ESCAPE
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DOI：
10.1021/bi00057a011
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发表时间：
1993-02-16
期刊：
影响因子：
2.9
通讯作者：
CHANCE, MR
中科院分区：
文献类型：
--
作者：
CHEN, E;CHANCE, MR
用连续波激光在442 nm波段测量了三种钴胺化合物在好氧和厌氧条件下光解钴碳键的量子产率。在有氧条件下，初始均解产物Co（II）钴胺素被氧捕获形成水钴胺素。在厌氧条件下，使用过量的自由基捕获试剂2,2,6,6-四甲基-1-哌替啶氧基清除碳自由基，并允许检测钴（II）光产物。在厌氧条件下测量的5'-脱氧腺苷钴胺素（phi(Co-Calpha),442 = 0.20 +/- 0.03）和甲基钴胺素（phi(Co-Calpha),442 = 0.35 +/- 0.03）的量子产率与在好氧条件下获得的值(phi（Co-Calpha),442 = 0.19 +/- 0.04和phi(Co-Calpha),442 = 0.36 +/- 0.04）一致。此外，5'-脱氧腺苷钴胺素及其碱基衍生物（phi(Co-Calpha),442 = 0.045 +/- 0.015）的量子产率值与在纳秒时间尺度上获得的量子产率值相匹配[Chen， E., & Chance， M. R. (1990) J. Biol。化学学报，26(6):1287 -12994。比较5'-脱氧腺苷钴胺素和甲基钴胺素在水中与乙二醇厌氧得到的量子产率，前者钴胺素减少了4倍，后者没有变化。这些量子产率是根据时间无关的自由基分离距离来评估的。
Quantum yields of photolysis of the cobalt-carbon bond for three cobalamin compounds were measured with a continuous-wave laser at 442 nm under both aerobic and anaerobic conditions. Aerobically, the initial homolysis product, Co(II) cobalamin, is trapped by oxygen to form aquocobalamin. Use of an excess of the radical trapping reagent 2,2,6,6-tetramethyl-1-piperidinyloxyl, under anaerobic conditions, scavenges the carbon radical and allows detection of the cobalt(II) photoproduct. Quantum yields measured under anaerobic conditions for 5'-deoxyadenosylcobalamin (phi(Co-Calpha),442 = 0.20 +/- 0.03) and methylcobalamin (phi(Co-Calpha),442 = 0.35 +/- 0.03) are in agreement with the values obtained under aerobic conditions (phi(Co-Calpha),442 = 0.19 +/- 0.04 and phi(Co-Calpha),442 = 0.36 +/- 0.04, respectively). Additionally, the quantum yield values for 5'-deoxyadenosylcobalamin and its base-off derivative (phi(Co-Calpha),442 = 0.045 +/- 0.015) match those obtained on a nanosecond time scale [Chen, E., & Chance, M. R. (1990) J. Biol. Chem. 256, 12987-12994]. A comparison of quantum yields obtained anaerobically for 5'-deoxyadenosylcobalamin and methylcobalamin in H2O versus ethylene glycol shows a 4-fold decrease for the former cobalamin and no change for the latter. These quantum yields are evaluated in terms of time-independent radical separation distances.