Institute of Physics, Faculty of Science, University of South Bohemia, Branišovská 1760, 370 05, České Budějovice, Czech Republic.
Institute of Chemistry, Faculty of Science, University of South Bohemia, Branišovská 1760, 370 05, České Budějovice, Czech Republic.
Chemphyschem. 2021 Mar 3;22(5):471-480. doi: 10.1002/cphc.202000982. Epub 2021 Feb 2.
Carotenoids are molecules with rich photophysics that are in many biological systems involved in photoprotection. Yet, their response to excess energy excitation is only scarcely studied. Here we have explored excited state properties of three keto-carotenoids, echinenone, canthaxanthin and rhodoxanthin after excess energy excitation to a singlet state absorbing in UV. Though the basic spectral features and kinetics of S , hot S , relaxed S states remain unchanged upon UV excitation, the clear increase of the S* signal is observed after excess energy excitation, associated with increased S* lifetime. A multiple origin of the S* signal, originating either from specific conformations in the S state or from a non-equilibrated ground state, is confirmed in this work. We propose that the increased amount of energy stored in molecular vibrations, induced by the UV excitation, is the reason for the enhanced S* signal observed after UV excitation. Our data also suggest that a fraction of the UV excited state population may proceed through a non-sequential pathway, bypassing the S state.
类胡萝卜素是具有丰富光物理性质的分子，在许多生物系统中参与光保护。然而，它们对过剩能量激发的反应仅被很少研究。在这里，我们研究了三种酮类胡萝卜素，echinenone、canthaxanthin 和 rhodoxanthin 在吸收 UV 光的单重激发态后过剩能量激发的激发态性质。尽管在 UV 激发后，S 态、热 S 态、松弛 S 态的基本光谱特征和动力学保持不变，但在过剩能量激发后观察到 S信号明显增加，同时 S寿命增加。本工作证实了 S信号的多个来源，要么源自 S 态中的特定构象，要么源自非平衡基态。我们提出，UV 激发诱导的分子振动中储存的能量增加是观察到 UV 激发后 S信号增强的原因。我们的数据还表明，一部分 UV 激发态可能通过非连续途径进行，绕过 S 态。
