We describe a molecular mechanism tuning the functional properties of chlorophyll a (Chl-a) molecules in photosynthetic antenna proteins. Light-harvesting complexes from photosystem II in higher plants - specifically LHCII purified with α- or β-dodecyl-maltoside, along with CP29 - were probed by low-temperature absorption and resonance Raman spectroscopies. We show that hydrogen bonding to the conjugated keto carbonyl group of protein-bound Chl-a tunes the energy of its Soret and Qy absorption transitions, inducing red-shifts that are proportional to the strength of the hydrogen bond involved. Chls-a with non-H-bonded keto C131 groups exhibit the blue-most absorption bands, while both transitions are progressively red-shifted with increasing hydrogen-bonding strength - by up 382 & 605 cm-1 in the Qy and Soret band, respectively. These hydrogen bonds thus tune the site energy of Chl-a in light-harvesting proteins, determining (at least in part) the cascade of energy transfer events in these complexes.

中文翻译：

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通过与叶绿素a的氢键来调节天线功能。

我们描述了一种调节光合作用天线蛋白中叶绿素a（Chl-a）分子的功能特性的分子机制。通过低温吸收和共振拉曼光谱法检测了高等植物中来自光系统II的光收集复合物-特别是用α-或β-十二烷基-麦芽糖苷纯化的LHCII，以及CP29-进行了探测。我们显示，氢键结合到蛋白质结合的Chl-a的共轭酮羰基上，可调节其Soret和Qy吸收跃迁的能量，并引起与所涉及的氢键强度成正比的红移。带有非H键合的酮C131基团的Chls-a显示最蓝的吸收带，而两个跃迁都随着氢键强度的增加而逐渐红移-在Qy和Soret带中分别增加了382和605 cm-1。分别。