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首页> 外文期刊>Biochemistry >Primary processes of charge separation in reaction centers of YM210L/FM197Y and YM210L mutants of Rhodobacter sphaeroides
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Primary processes of charge separation in reaction centers of YM210L/FM197Y and YM210L mutants of Rhodobacter sphaeroides

机译：球形红球菌YM210L / FM197Y和YM210L突变体反应中心电荷分离的主要过程

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摘要

Difference femtosecond absorption spectroscopy with 20-fsec temporal resolution was applied to study a primary stage of charge separation and transfer processes in reaction centers of YM210L and YM210L/FM197Y site-directed mutants of the purple bacterium Rhodobacter sphaeroides at 90 K. Photoexcitation was tuned to the absorption band of the primary electron donor P at 880 nm. Coherent oscillations in the kinetics of stimulated emission of P* excited state at 940 nm and of anion absorption of monomeric bacteriochlorophyll B A - at 1020 nm were monitored. The absence of tyrosine YM210 in RCs of both mutants leads to strong slowing of the primary reaction P* [arrow right] P+B A - and to the absence of stabilization of separated charges in the state P+B A - . Mutation FM197Y increases effective mass of an acetyl group of pyrrole ring I in the bacteriochlorophyll molecule PB of the double mutant YM210L/FM197Y by a hydrogen bond with OH-TyrM197 group that leads to a decrease in the frequency of coherent nuclear motions from 150 cm-1 in the single mutant YM210L to 100 cm-1 in the double mutant. Oscillations with 100-150 cm-1 frequencies in the dynamics of the P* stimulated emission and in the kinetics of the reversible formation of P+B A - state of both mutants reflect a motion of the PB molecule relatively to PA in the area of mutual overlapping of their pyrrole rings I. In the double mutant YM210L/FM197Y the oscillations in the P* emission band and the B A - absorption band are conserved within a shorter time 0.5 psec (1.5 psec in the YM210L mutant), which may be a consequence of an increase in the number of nuclei forming a wave packet by adding a supplementary mass to the dimer P. [PUBLICATION ABSTRACT]
机译：差分飞秒吸收光谱技术以20毫秒的时间分辨率来研究电荷分离和转移过程的主要阶段，该过程是在90 K的紫色细菌球形红球菌YM210L和YM210L / FM197Y定点突变体的反应中心进行的。主电子给体P在880nm处的吸收带。监测了在940 nm激发的P *激发态的发射和1020 nm的单体细菌叶绿素B A-的阴离子吸收的动力学的相干振荡。两个突变体的RC中都不存在酪氨酸YM210会导致初级反应P * [右箭头] P + BA-的强烈减慢，并且导致P + BA-状态下分离电荷的稳定化。突变FM197Y通过与OH-TyrM197基团的氢键增加了双突变体YM210L / FM197Y的细菌叶绿素分子PB中吡咯环I乙酰基的有效质量，从而导致相干核运动的频率从150 cm-降低单突变体YM210L中为1，双突变体中为100 cm-1。 P *激发发射的动力学和P + BA可逆形成的动力学中100-150 cm-1频率的振荡-两个突变体的状态都反映了PB分子相对于PA在共同区域中的运动在双突变体YM210L / FM197Y中，P *发射带和BA-吸收带中的振荡在较短的时间内保持了0.5 psec（YM210L突变体为1.5 psec），这可能是结果通过向二聚体P增加补充质量来增加形成波包的核数。[出版物摘要]

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