Götze Jan P, Petry Simon, Reiter Sebastian, Lokstein Heiko, de Vivie-Riedle Regina
Freie Universität Berlin, Fachbereich Biologie Chemie Pharmazie, Physikalische und Theoretische Chemie, Arnimallee 22, Berlin 14195, Germany.
Ludwig-Maximilians-Universität München, Department Chemie, Butenandtstr. 5-13, Munich 81377, Germany.
J Phys Chem B. 2025 Aug 7;129(31):7884-7895. doi: 10.1021/acs.jpcb.5c02465. Epub 2025 Jul 23.
The current interpretation of excitation energy transfer (EET) processes in natural photosynthesis generally relies on Kasha's rule, suggesting that internal conversion (IC) processes usually outpace any EET between higher excited states. It is, however, known from research on artificial systems that Kasha's rule does not apply to many dyes, especially when found in assembled clusters analogous to photosynthetic chlorophyll (Chl)-protein complexes. In this contribution, a semiempirical Förster-type model is applied to otherwise well-investigated pigments of natural photosynthesis (Chls , , and various carotenoids). Strong potential for anti-Kasha processes is identified in all investigated pigments, based on their high Coulomb coupling elements, similar to compounds with already known anti-Kasha properties. The pigments are further found to form strongly delocalized excitons, especially between the higher excited states usually responsible for anti-Kasha pathways. Test calculations with different pigment compositions for various natural light harvesting complexes (LHCII, CP24, CP26, CP29, FCP) demonstrate how the higher band EET network and absorbance could be affected by the presence of accessory pigments: Chl -only networks should perform anti-Kasha EET, but this is suppressed by the presence of accessory pigments via several mechanisms (exciton disruption, spectral competition, energy sinks and fast, non-Chl IC). The apparent "special" behavior of photosynthetic systems is thus resolved as the result of pigment mixtures.
目前对自然光合作用中激发能转移（EET）过程的解释通常依赖于卡莎规则，这表明内转换（IC）过程通常比任何更高激发态之间的EET更快。然而，从人工系统的研究中可知，卡莎规则并不适用于许多染料，尤其是当它们存在于类似于光合叶绿素（Chl）-蛋白质复合物的组装簇中时。在本论文中，一个半经验的福斯特型模型被应用于自然光合作用中其他已得到充分研究的色素（叶绿素a、b、c以及各种类胡萝卜素）。基于其高库仑耦合元素，在所有研究的色素中都发现了强烈的反卡莎过程潜力，这与具有已知反卡莎性质的化合物类似。进一步发现这些色素会形成强离域激子，特别是在通常负责反卡莎途径的更高激发态之间。对各种天然光捕获复合物（LHCII、CP24、CP26、CP29、FCP）使用不同色素组成进行的测试计算表明，辅助色素的存在会如何影响更高能带的EET网络和吸光度：仅叶绿素的网络应进行反卡莎EET，但这会通过几种机制（激子破坏、光谱竞争、能量汇以及快速的非叶绿素a IC）被辅助色素的存在所抑制。因此，光合系统明显的“特殊”行为被解释为色素混合物的结果。
