Martin J L, Migus A, Poyart C, Lecarpentier Y, Astier R, Antonetti A
Proc Natl Acad Sci U S A. 1983 Jan;80(1):173-7. doi: 10.1073/pnas.80.1.173.
Photolysis of HbCO, MbCO, and CO-protoheme has been investigated by measuring transient differential spectra and kinetics of induced absorption after excitation with a 250-fsec laser pulse at 307 nm. Probing was performed by a part of a continuum pulse between 395 and 445 nm. Photodissociation of the three liganded species occurred within the pulse duration. By contrast, the formation of deoxy species appeared with a mean (+/- SD) response time of 350 +/- 50 fsec. This time constant was identical for the three species and independent of the presence or absence of the protein structure. Our results suggest the formation of a transient high-spin in plane iron (II) species which relaxes in 350 fsec to a high-spin stable state with concerted kinetics of CO departure and iron displacement. The spin transition is suspected to occur via liganded excited states which relax in part to non-reactive states with a 3.2-psec time constant.
通过测量瞬态差分光谱以及在307nm处以250飞秒激光脉冲激发后诱导吸收的动力学,对HbCO、MbCO和CO-原血红素的光解进行了研究。探测是通过395至445nm之间的连续脉冲的一部分进行的。三种配体物种的光解离在脉冲持续时间内发生。相比之下,脱氧物种的形成出现的平均(±标准差)响应时间为350±50飞秒。这个时间常数对于这三种物种是相同的,并且与蛋白质结构的存在与否无关。我们的结果表明形成了一种瞬态平面内高自旋铁(II)物种,该物种在350飞秒内弛豫到高自旋稳定状态,同时伴随着CO离去和铁位移的协同动力学。自旋转变被怀疑是通过配体激发态发生的,这些激发态部分弛豫到具有3.2皮秒时间常数的非反应态。