Study of exotic chlorophylls in photosynthesis

We found a novel Zn-containing bacteriochlorophyll in an aerobic bacterium Acidophilium rubrum growing under acidic conditions。我们对HPLC、光学光谱学、循环流变学、快速原子轰炸质量光谱学和E-D11 E-D1 H-NMR测量的这种颜料的分子结构没有意义。颜料的结构被确认为含有phytol的生物化学，除了中央金属是锌（Zn） instead of magnesium （Mg）。主要颜料的两个天线系统和反应中心（RC）在高植物和细菌化学（BChls）中存在氯丁胺（Chls）中的氯丁胺（Chls）。Chls和BChls一直不太可能相信是替代氯林或细菌氯林宏环的Mg复合体，具有无金属氯林和BChla、称为Phe a和BPhe a的单点例外，其行为是高植物2中的主电子接收器和紫细菌的RC。However， we found a novel BChl a containing Zn as the central metal in an aerobic bacterium Acidophilium rubrum growing under low pH. We discussed the reason for the choice of Zn as the central metal in A. Rubrum，参考了Zn-BChl a作为光谱学和redox性质的这类物理化学行为; Zn-BChl a与含有HCl的正常BChl a的Rhodobacter Sphaeroides（去金属化）速率进行比较。Zn-BChl a was pheophytinized roughly 10-D16-fold more slowly than BChl a.锌的高抵抗力-BChl a对酸可能是原因的一部分。Rubrum，生活在低pH值的介质中，选择锌作为中心金属。

We found a novel Zn-containing bacteriochlorophyll in an aerobic bacterium Acidiphilium rubrum growing under acidic conditions. We have unambiguously determined the molecular structure of this pigment by HPLC, optical spectroscopy, circular dichroism, fast atom bombardment mass spectrometry and ィイD11ィエD1H-NMR measurements. The structure of the pigment was confirmed to be identical to that of bacteriochlorophyll a esterified with phytol, except that the central metal is zinc (Zn) instead of magnesium (Mg).The major pigments of both antenna systems and reaction centers (RCs) are chlorophylls (Chls) in higher plants and bacteriochlorophylls (BChls) in photosynthetic bacteria. Chls and BChls have been unquestionedly believed to be Mg complexes of substituted chlorin or bacteriochlorin macrocycles, with a sole exception of metal-free Chl a and BChl a, called Phe a and BPhe a, that act as primary electron acceptors in photosystem 2 of higher plants and in the RC of purple bacteria. However, we found a novel BChl a containing Zn as the central metal in an aerobic bacterium Acidiphilium rubrum growing under low pH. We discussed the reason for the choice of Zn as the central metal in A. rubrum, referring to such physicochemical behaviors of Zn-BChl a as the spectroscopic and redox properties.Zn-BChl a from Acidiphilium rubrum was compared with the normal BChl a from Rhodobacter sphaeroides for the pheophytinization (de-metalation) rate in aqueous acetone containing HCl. Zn-BChl a was pheophytinized roughly 10ィイD16ィエD1-fold more slowly than BChl a. The high resistance of Zn-BChl a to acid may be one of the reasons why A. rubrum, living in media of low pH, chose Zn instead of Mg as the central metal.