Analysis of Light-Induced Absorbance Changes in the Near-Infrared Spectral Region I. Characterization of Various Components in Isolated Chloroplasts
Analysis of Light-Induced Absorbance Changes in the Near-Infrared Spectral Region I. Characterization of Various Components in Isolated Chloroplasts
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近红外光谱区光致吸光度变化的分析 I. 分离叶绿体中各种成分的表征
DOI：
10.1515/znc-1991-3-413
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发表时间：
1991
期刊：
影响因子：
--
通讯作者：
U. Schreiber
中科院分区：
文献类型：
--
作者：
C. Klughammer;U. Schreiber
以脉冲发光二极管为调制测量光源，分析了菠菜叶绿体在近红外(700-950 nm)区域的光诱导吸光度变化。当叶绿体处于耦合状态时，光诱导信号以相对较慢的散射变化为主，表现为平坦的差光谱。更具体的变化可以通过更快的诱导和松弛动力学以及在存在防止分散变化的瓦林霉素/黑曲霉素时加以区分。除了主要的P700变化外，在703 nm附近有一个窄的漂白带，在750-850 nm之间有一个宽的吸光度增加(峰值在815 nm)，在近红外光谱中还发现了以下吸光度的变化：1)由于塑料花青素(PC)的氧化导致吸光度增加，光谱相对平坦。2)与铁氧还蛋白不同，吸光度的降低反映了PSI的低电势受体的减少。3)表明吸光度下降的场在730 nm附近达到峰值，其性质与p515的性质相一致。4)暗适应和厌氧条件刺激的非偶联剂不敏感的吸光度降低，其差谱类似于铁氧还蛋白还原。通过氧化还原滴定确定了P700和PC在总氧化还原差谱中的相对贡献。在706 nm、815 nm和950 nm处，P700/pC分别为-119/19、67/37和31/69。根据这些比例和摩尔消光系数，确定了摩尔P700/PC的化学计量比为1/3。
Light-induced absorbance changes in the near-infrared (NIR ) spectral region (700-950 nm) are analyzed in isolated spinach chloroplasts using pulsed light-emitting diodes as modulated measuring light sources. With chloroplasts under coupled conditions the light-induced signal is dominated by a relatively slow scattering change displaying a flat difference spectrum. More specific changes can be distinguished by faster induction and relaxation kinetics and in the presence of valinomycin/nigericin which prevents scattering changes. Besides the dominant P700 change, with a narrow bleaching band around 703 nm and a broad absorbance increase between 750 and 850 nm (peak at 815 nm) the following absorbance changes were identified in the NIR: 1) An absorbance increase caused by plastocyanin (PC) oxidation, with a relatively flat spectrum. 2) An absorbance decrease gaining amplitude towards longer wavelengths, which reflects reduction of a low potential acceptor of PSI different from ferredoxin. 3) A field indicating absorbance decrease peaking around 730 nm, the properties of which correspond to those of P515. 4) An uncoupler insensitive absorbance decrease stimulated by dark adaptation and anaerobic conditions, the difference spectrum of which resembles that of ferredoxin reduction. The relative contributions of P700 and PC to the overall oxidized-reduced difference spectrum are determined by redox titration. At 706 nm, 815 nm and 950 nm the P 700/PC is - 119/ 19, 67/37 and 31/69, respectively. From these ratios and the molar extinction coefficients a molar P 700/PC stoichiometry of 1 /3 is determined.