Chernoff D A, Hochstrasser R M, Steele A W
Proc Natl Acad Sci U S A. 1980 Oct;77(10):5606-10. doi: 10.1073/pnas.77.10.5606.
The photolysis of HbO2 and HbCO has been studied by measuring transient absorption spectra in the Soret region after excitation with picosecond pulses at 530 nm. Dissociation occurred promptly in both cases, followed (for HbO2) by geminate recombination of ca. 40% of the photodissociated O2 with a lifetime of 200 +/- 70 psec (25 degrees C). No recombination of Hb + CO was observed up to 1200 psec after photolysis. The HbO2 and HbCO photoproduct spectra were broader, weaker, and red-shifted in comparison to the spectrum of stable Hb and Gibson's fast-reacting form, Hb. For HbO2 the spectrum was initially much broader to longer wavelengths but relaxed to a constant shape within 90 psec, whereas for HbCO there was no spectral evolution. The photophysics is analyzed by considering the effect of spin constraints as well as spin--orbit coupling and orbital correlation among the various electronic states of liganded and deoxy hemoglobins. The small quantum yield of HbO2 dissociation is not primarily due to rebinding but rather to electronic relaxation to nonreactive states.
通过在530nm处用皮秒脉冲激发后测量Soret区域的瞬态吸收光谱，研究了HbO₂和HbCO的光解。在这两种情况下，解离都迅速发生，随后（对于HbO₂）约40%的光解离O₂发生双生复合，其寿命为200±70皮秒（25℃）。光解后1200皮秒内未观察到Hb + CO的复合。与稳定Hb和吉布森快速反应形式Hb的光谱相比，HbO₂和HbCO的光产物光谱更宽、更弱且发生红移。对于HbO₂，光谱最初在更长波长处更宽，但在90皮秒内弛豫到恒定形状，而对于HbCO则没有光谱演化。通过考虑自旋限制以及配体化和脱氧血红蛋白各种电子态之间的自旋 - 轨道耦合和轨道相关性来分析光物理过程。HbO₂解离的小量子产率主要不是由于重新结合，而是由于电子弛豫到非反应态。
