Time-Resolved Spectroscopic Studies of B12 Coenzymes: The Photolysis of Methylcobalamin Is Wavelength Dependent
Time-Resolved Spectroscopic Studies of B12 Coenzymes: The Photolysis of Methylcobalamin Is Wavelength Dependent
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B12 辅酶的时间分辨光谱研究：甲钴胺的光解作用与波长相关
DOI：
10.1021/jp992358r
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发表时间：
1999
影响因子：
3.3
通讯作者：
R. Sension
中科院分区：
文献类型：
--
作者：
J. Shiang;L. Walker;N. Anderson;and R G Cole;R. Sension
飞秒至纳秒瞬态吸收光谱已被用于研究B12辅酶，甲基钴胺素和5 '-脱氧腺苷钴胺素的主要光化学。比较了近紫外（400 nm）和可见光（520 - 530 nm）激发波长下的光解。测量进行了飞秒时间分辨率，覆盖时间延迟高达9 ns。甲钴胺的光化学被发现强烈地依赖于激发波长，而腺苷钴胺素的光化学在所研究的范围内基本上是波长无关的。在400 nm处激发甲钴胺素导致在迅速的键均裂和形成亚稳的cob（III）维生素光产物之间的分配，如早先报道的[步行者，L.一、II; Jarrett，J. T.;安德森，N.一、Pullen，S. H.的;马修斯河G.地;森西翁河J·J·Am. 1998，120，3597 - 3603]。甲钴胺在可见αβ-波段520 nm处的激发仅导致亚稳态cob（III）alamin p.
Femtosecond to nanosecond transient absorption spectroscopy has been used to investigate the primary photochemistry of the B12 coenzymes, methylcobalamin and 5‘-deoxyadenosylcobalamin. Photolysis at excitation wavelengths in the near UV (400 nm) and visible (520−530 nm) are compared. Measurements were performed with femtosecond time resolution covering time delays of up to 9 ns. The photochemistry of methylcobalamin is found to depend strongly on excitation wavelength, while the photochemistry of adenosylcobalamin is essentially wavelength independent over the range studied. Excitation of methylcobalamin at 400 nm results in a partitioning between prompt bond homolysis and formation of a metastable cob(III)alamin photoproduct as reported earlier [Walker, L. A., II; Jarrett, J. T.; Anderson, N. A.; Pullen, S. H.; Matthews, R. G.; Sension, R. J. J. Am. Chem. Soc. 1998, 120, 3597−3603]. Excitation of methylcobalamin at 520 nm in the visible αβ-band results only in formation of the metastable cob(III)alamin p...