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首页> 外文期刊>Biochemistry >Redox titration of all electron carriers of cytochrome c oxidase by Fourier transform infrared spectroscopy
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Redox titration of all electron carriers of cytochrome c oxidase by Fourier transform infrared spectroscopy

机译：通过傅里叶变换红外光谱法通过CoCochrome C氧化酶的所有电子载体的氧化还原滴定

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Electrochemical redox titrations of cytochrome c oxidase from Paraccocus denitrificans were performed by attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy. The majority of the differential infrared absorption features may be divided into four groups, which correlate with the redox. transitions of the four redox centers of the enzyme. Infrared spectroscopy has the advantage of allowing one to measure independent alterations in redox centers, which are not well separated, or even observed, by other spectroscopic techniques. We found 12 infrared bands that titrated with the highest observed midpoint redox potential (E-m = 412 mV at pH 6.5) and which had a pH dependence of 52 mV per pH unit in the alkaline region. These bands were assigned to be linked to the CUB center. We assigned bands: to the CUA center that showed a pH-independent E-m of 250 mV. Two other groups of infrared differential bands reflected redox transitions of the two heme groups and showed a more complex behavior. Each of them included two parts, corresponding to high- and low-potential redox transitions. For the bands; representing heme a, the ratio of high- to low-potential components was ca. 3:2; for heme a(3) this ratio was ca. 2:3. Taking into account the redox interactions between the hemes, these ratios yielded a difference in E-m of 9 mV between the hemes (359 mV for heme a; 350 mV for heme a(3) at pH 8.0). The extent of the redox interaction between the hemes (-115 mV at pH 8.0) was found to be pH-dependent. The pH dependence of the E-m values for the two hemes was the same and about two times smaller than the theoretical one, suggesting that an acid/base group binds a proton upon reduction of either heme. The applied approach allowed assignment of infrared bands in each of the four groups to vibrations of the hemes, ligands of the redox centers, amino acid residues, and/or protein backbone. For example, the well-known band shift at 1737/1746 cm(-1) corresponding to the protonated glutamic acid E278 correlated with oxidoreduction of heme a.
机译：通过减弱的总反射抗傅里叶变换红外（ATR-FTIR）光谱来进行来自浆脱氮网的细胞色素C氧化酶的电化学氧化铈滴定。大多数差分红外吸收特征可以分为四组，与氧化还原相关。四种氧化还原中心的转变。红外光谱具有允许一个人通过其他光谱技术测量氧化还原中心的独立改变，或者通过其他光谱技术来测量氧化还原中心的独立改变。我们发现12个红外条带，其滴定在最高观察到的中点氧化还原电位（E-M = 412mV，在pH 6.5时），其在碱性区域中具有52mV的pH依赖性。这些频段被分配到与Cub中心联系起来。我们分配了乐队：到CUA中心，该中心显示了一个纯粹的250 mV的I-M。另外两组红外差分带反射了两种血红素组的氧化还原转变，并显示出更复杂的行为。它们中的每一个都包括两个部分，对应于高潜能的氧化还原转换。对于乐队;代表血红素A，高至低电平部件的比例是CA。 3：2;对于血红素A（3）该比例是CA。 2：3。考虑到血液之间的氧化还原相互作用，这些比率在血液（359mV用于血红液A之间的9mV中产生的差异（359mV; pH8.0的血红素A（3））。发现溶质之间的氧化还原相互作用的程度（pH8.0在pH8.0下）依赖于pH依赖性。两种血液的E-M值的pH依赖性比理论均相同，并且暗示酸/碱基在减少血红素时结合质子。所施加的方法允许在四组中的每一个中分配红外条，氧化还原中心，氨基酸残基和/或蛋白质骨架的振动。例如，对应于与血红素A的氧化氧化的质子化谷氨酸E278对应于1737/1746cm（-1）的众所周知的带偏移。

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