Taylor Natasha, Kassal Ivan
School of Chemistry and University of Sydney Nano Institute , University of Queensland , QLD 4072 , Australia.
School of Chemistry , University of Sydney Nano Institute , University of Sydney , NSW 2006 , Australia . Email:
Chem Sci. 2019 Aug 26;10(41):9576-9585. doi: 10.1039/c9sc03712h. eCollection 2019 Nov 7.
All photosynthetic organisms convert solar energy into chemical energy through charge separation in dimeric reaction centres. It is unknown why early reaction centres dimerised and completely displaced their monomeric ancestors. Here, we discuss several proposed explanations for reaction-centre dimerism and conclude-with only weak assumptions about the primordial dimerisation event-that the most probable explanation for the dimerism is that it arose because it enhanced light-harvesting efficiency by deepening the excitonic trap, , by enhancing the rate of exciton transfer from an antenna complex and decreasing the rate of back transfer. This effect would have outweighed the negative effect dimerisation would have had on charge transfer within the reaction centre. Our argument implies that dimerisation likely occurred after the evolution of the first antennas, and it explains why the lower-energy state of the special pair is bright.
所有光合生物都通过二聚体反应中心的电荷分离将太阳能转化为化学能。目前尚不清楚早期反应中心为何会二聚化并完全取代其单体祖先。在此，我们讨论了几种关于反应中心二聚化的解释，并得出结论——仅基于对原始二聚化事件的微弱假设——二聚化最可能的解释是，它通过加深激子陷阱来提高光捕获效率，即通过提高激子从天线复合物转移的速率并降低反向转移的速率。这种效应超过了二聚化对反应中心内电荷转移可能产生的负面影响。我们的观点意味着二聚化可能发生在第一个天线进化之后，并且它解释了特殊对的较低能量状态为何是明亮的。
