Time-resolved absorption spectra from the femtoscecond to sub-millisecond time regimes were recorded in order to eluciate the photoprotective mechanisms of carotenoid (spirilloxanthin) in core LH1 light-harvesting pigment-protein complexes from a purple photosynthetic bacterium, Rhodospirillum (Rsp.) rubrum. Carotenoids can prevent the production of singlet oxygen by rapidly quenching the Bchl a triplet state. Through this triplet-triplet energy-transfer reaction the carotenoid is believed to protect the biological system from exposure to excess light. We set out to investigate this paricular function in the purple bacterium, Rsp. rubrum strain S1. We also investigated Rsp. rubrum strain G9+, which is the carotenoidless mutant of Rsp. rubrum, to make sure that the carotenoid is truly playing this important role. As a result, we could demonstrate that strain S1 realizes nearly 100% excitation energy transfer from triplet Bchl a to carotenoid. In addition, we found another major excited state deactivation channel of carotenoids, which takes away excess energy directly from the singlet excited state of Bchl a and so prevents the production of triplet excited Bchl a.

记录了从飞秒到亚毫秒级时间范围的时间分辨吸收光谱，以阐明类胡萝卜素（螺黄质）在紫色光合细菌Rhodospirillum（Rsp。）rubrum的核心LH1光捕获色素-蛋白质复合物中的光保护机制。。类胡萝卜素可以通过快速淬灭Bchl的三重态来防止单线态氧的产生。通过这种三重态-三重态能量转移反应，类胡萝卜素被认为可以保护生物系统免受过量光的照射。我们着手研究紫色细菌Rsp中的这种特殊功能。风疹菌株S1。我们还调查了Rsp。风疹G9 +菌株，是Rsp的无类胡萝卜素突变体。，以确保类胡萝卜素确实发挥了重要作用。其结果是，我们可以证明应变S1实现了从三重的Bchl近100％的激发能量传递一个类胡萝卜素。此外，我们发现了另一个类胡萝卜素的主要激发态失活通道，该通道可以直接从Bchl a的单重态激发态中吸收多余的能量，从而阻止了三重激发态Bchl a的产生。