Ultrafast excited state dynamics of nonfluorescent cyclopheophorbide-a enol, a catabolite of chlorophyll-a detoxified in algae-feeding aquatic microbes†,Photochemical & Photobiological Sciences

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Ultrafast excited state dynamics of nonfluorescent cyclopheophorbide-a enol, a catabolite of chlorophyll-a detoxified in algae-feeding aquatic microbes†
Photochemical & Photobiological Sciences ( IF 2.7 ) Pub Date : 2018-09-24 00:00:00 , DOI: 10.1039/c8pp00173a
Chikashi Ota _{1,

2,

3,

4} , Keita Sugihara _{1,

2,

3,

4} , Yusuke Kinoshita _{2,

3,

4,

5} , Yuichiro Kashiyama _{2,

3,

4,

5,

6} , Yutaka Nagasawa _{1,

2,

3,

4} , Hitoshi Tamiaki _{2,

3,

4,

5}

Affiliation

For photosynthetic organisms that nourish the earth's biosphere, chlorophylls (Chls) are the major pigments utilized for light harvesting and primary charge separation. Although Chl molecules are effective photosensitizers, they are inevitably phototoxic to living organisms due to the facile generation of highly oxidative singlet oxygen (¹O₂) through triplet energy transfer from their photoexcited states to oxygen molecules. Such phototoxicity of Chls is a major problem for translucent microbes that feed on photosynthetic algae. Recently, it has been reported that the metabolic conversion of Chls-a/b to 13²,17³-cyclopheophorbide-a/b enols (cPPB-a/bEs) is the detoxification mechanism for algivorous protists. cPPB-a/bEs are colored π-conjugated cyclic tetrapyrroles but are nonfluorescent due to efficient nonradiative decay. In this study, femtosecond time-resolved transient absorption spectroscopy was applied to cPPB-aE with the aim of understanding its quenching mechanism. As a result, we have captured the ultrafast generation of an intermediate state (∼140 fs) that leads to the rapid internal conversion to the ground state (∼450 fs).

中文翻译：

的非荧光cyclopheophorbide-超快激发态动力学一个烯醇，叶绿素的分解代谢物一脱毒在藻类馈送水生微生物†

对于滋养地球生物圈的光合生物而言，叶绿素（Chls）是用于光收集和初级电荷分离的主要色素。尽管Chl分子是有效的光敏剂，但由于通过三重态能量从光激发态转移到氧分子上而容易产生高氧化性单线态氧（¹ O ₂），它们对生物体不可避免地具有光毒性。对于以光合作用藻为食的半透明微生物，Chls的这种光毒性是一个主要问题。最近，已经报道，Chls-的代谢转化一个/ b至13 ²，17 ³ -cyclopheophorbide-一个/ b烯醇（cPPB- a / b Es）是食盐生物的解毒机制。cPPB- a / b Es为有色π共轭环状四吡咯，但由于有效的非辐射衰变而呈非荧光性。在这项研究中，飞秒时间分辨瞬态吸收光谱法被应用于cPPB- a E，以了解其猝灭机理。结果，我们捕获了中间状态（〜140 fs）的超快生成，该状态导致内部快速转换为基态（〜450 fs）。

更新日期：2018-09-24

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