锌细菌叶绿素a和镁细菌叶绿素a氧化还原势的比较

在光合体系中,叶绿素分子可以和不同的氨基酸配位.笔者用密度泛函方法,研究了不同氨基酸与镁细菌叶绿素a和锌细菌素a配位时,离解能和氧化还原势的变化情况.计算及分析结果表明,镁细菌叶绿素a分子中的金属镁原子被锌原子取代后,氧化还原势变化不大.并且不同氨基酸分子与2种细菌叶绿素分子配位时,所引起氧化还原势的变化可以弥补因镁被锌取代所引起的变化.这2种互补的作用使得锌细菌叶绿素a分子在光合作用中仍然是一种很好的电子传递体.最后用TDDFT方法,计算了2种细菌叶绿素a分子在气相中的吸收光谱.结果表明锌细菌叶绿素a的吸收光谱相对于镁细菌叶绿素a的吸收光谱有6～7nm的蓝移,这与实验结果相吻合.

The comparison of redox potential between zinc-bacteriochlorophylla and magnesium-bacteriochlorophylla

Chlorophylls can coordinate to different kinds of aminophenols in nature photosystem.To understand how aminophenols affect chlorophylls,we calculated the changes of redox potential when bacteriochlorophyll coordinates to different kinds of amino acid molecules using density function theory.According to our calculation,we found that the changes of redox potential are not obvious when the centural metal atom magnesium was changed into zinc.And the changes can be remedied by the coordination of aminophenol.These two kinds of collaboration effects makes zinc-bacteriochlorophylla a good electron carrier in nature photosystem.Time-dependent density functional theory（TDDFT） have been used to calculate the absorption spectrum properties of zinc-bacteriochlorophylla and magnesium-bacteriochlorophylla in gas-phase.All the absorption bands of zinc-bacteriochlorophylla have a blue-shift of 6 to 7 nm compared with the absorption bands of magnesium-bacteriochlorophylla.