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首页> 外文期刊>Biochemistry >Deuteration effects on the in vivo EPR spectrum of the reduced secondary photosystem I electron acceptor A1 in cyanobacteria.
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Deuteration effects on the in vivo EPR spectrum of the reduced secondary photosystem I electron acceptor A1 in cyanobacteria.

机译：氘化作用对蓝细菌中还原的次级光系统I电子受体A1的体内EPR光谱的影响。

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The photoreduction of the secondary PSI electron acceptor A1 in vivo has recently been detected via X-band EPR spectroscopy in intact spinach chloroplasts and in marine cyanobacteria Synechococcus PCC 7002 [Klughammer, C., and Pace, R. J. (1997) Biochim. Biophys. Acta 1318, 133-144]. A further study of the A1- EPR spectrum of Synechococcus PCC 7002 at room temperature with higher-field resolution revealed partially resolved hyperfine structure which was dominated by 0.4 mT splittings of three equivalent protons. The hyperfine splitting was not significantly affected by incubation of the cyanobacteria in 2H2O medium for 20 h, but was absent in fully deuterated cyanobacteria that were grown in 2H2O medium. Anisotropic g-factors consistent with a phylloquinone radical were derived by spectra simulation. Biosynthetic protonation of quinones via the CH3 donor L-methionine in deuterated cells maintained hyperfine structure in the A1- spectrum, indicating the incorporation of CH3 groups in 60% of the deuterated, photoactive A1 molecules. Conversely, biosynthetic quinone deuteration via L-[methyl-d3]methionine in protonated cells led to the loss of the 0. 4 mT splittings in 54% of the A1 molecules. These observations confirm the conclusion of Heathcote et al. [(1996) Biochemistry 35, 6644-6650] of the identity of EPR-detected, photoreduced A1- in vivo with a phylloquinone (vitamin K1) radical in PSI. The partially resolved hyperfine structure of the A1- spectrum indicates an altered spin distribution in the bound vitamin K1- radical in vivo compared to that of unbound vitamin K1- in vitro.
机译：最近已经通过X波段EPR光谱法在完整的菠菜叶绿体和海洋蓝细菌Synechococcus PCC 7002中检测到了体内次要PSI电子受体A1的光还原[Klughammer，C。和Pace，R.J。（1997）Biochim。生物物理学。 Acta 1318，133-144]。对Synechococcus PCC 7002在室温下具有较高场分辨率的A1- EPR谱的进一步研究显示，部分分解的超精细结构以三个等效质子的0.4 mT分裂为主。蓝细菌在2H2O培养基中孵育20小时不会显着影响超细分裂，但是在2H2O培养基中生长的完全氘化的蓝细菌中则没有这种现象。通过光谱模拟推导了与叶醌基团一致的各向异性g因子。氘代细胞中通过CH3供体L-甲硫氨酸进行醌的生物合成质子化，在A1-光谱中保持超精细结构，表明60％的氘代光敏A1分子中CH3基团的结合。相反，质子化细胞中通过L- [甲基-d3]蛋氨酸进行的生物合成醌氘化导致54％的A1分子损失0. 4 mT裂口。这些观察结果证实了Heathcote等人的结论。 [（1996）Biochemistry 35，6644-6650]与PSI中的叶醌（维生素K1）自由基在体内进行EPR检测，光还原的A1-的同一性。与未结合的维生素K1-体外相比，A1光谱的部分分辨的超精细结构表明体内结合的维生素K1-自由基的自旋分布发生了变化。

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