Han Rui-Min, Wu Yi-Shi, Feng Juan, Ai Xi-Cheng, Zhang Jian-Ping, Skibsted Leif H
State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, People's Republic of China.
Photochem Photobiol. 2004 Sep-Oct;80(2):326-33. doi: 10.1562/2004-04-22-RA-147.
On direct photoexcitation, subpicosecond time-resolved absorption spectroscopy revealed that the 1B(u)-type singlet excited state of all-trans-lycopene in chloroform was about seven times more efficient than all-trans-beta-carotene in generating the radical cation. The time constant of radical cation generation from the 1B(u)-type state was found to be approximately 0.14 ps, a value that was comparable for the two carotenoids. On anthracene-sensitized triplet excitation, radical cation generation was found to be much less efficient for lycopene than for beta-carotene. A slow rising phase (20-30 micros) in the bleaching of ground-state absorption was common for both lycopene and beta-carotene in chloroform and was ascribed to an efficient secondary reaction with a solvent radical leading to the formation of carotenoid radical cations. The reverse ordering in the tendency of the excited states of different multiplicities for the two carotenoids to generate radical cations is discussed in relation to the two carotenoids as scavengers of free radicals.
在直接光激发下，亚皮秒时间分辨吸收光谱显示，氯仿中全反式番茄红素的1B(u)型单重激发态在产生自由基阳离子方面的效率比全反式β-胡萝卜素高约7倍。从1B(u)型态产生自由基阳离子的时间常数约为0.14皮秒，这一数值在两种类胡萝卜素中相当。在蒽敏化三重态激发下，发现番茄红素产生自由基阳离子的效率远低于β-胡萝卜素。氯仿中的番茄红素和β-胡萝卜素在基态吸收漂白过程中都有一个缓慢上升阶段（20 - 30微秒），这归因于与溶剂自由基的有效二级反应导致类胡萝卜素自由基阳离子的形成。结合两种类胡萝卜素作为自由基清除剂的作用，讨论了不同多重性激发态产生自由基阳离子倾向的相反顺序。
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