کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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5371744 | 1503960 | 2010 | 5 صفحه PDF | دانلود رایگان |
We have investigated the heterogeneity of the Fe(III)-Met80 linkage of horse heart ferricytochrome c by probing the 695Â nm charge transfer band with absorption and electronic circular dichroism (ECD) spectroscopy. In order to verify the connection between conformational substates of the Fe(III)-Met80 linkage and the 695Â nm band spectral heterogeneity, we have performed experiments as a function of pH (neutral and acidic) and temperature (room and 20Â K). At room temperature, the ECD spectrum is blue shifted with respect to the absorption one; the shift is more pronounced at acidic pH and is compatible with the presence of sub-bands. ECD measurements at 20Â K highlighted the heterogeneous nature of the 695Â nm band and provided direct experimental evidence for the presence of sub-bands. Indeed, while the absorption spectra remained deceivingly unstructured, the ECD spectra showed well resolved peaks and shoulders. A consistent fit of the 20Â K absorption and ECD spectra showed that five Gaussians (each centered at the same frequency in the absorption and ECD spectrum) are able to reproduce the observed lineshapes. A careful analysis of frequency shifts and intensity ratios of these sub-bands enabled us to identify at least three distinct sub-bands arising from taxonomic conformational substates of the Fe(III)-Met80 linkage. In view of the major influence of the Fe(III)-Met80 linkage on the redox potential of ferricytochrome c, we speculate that these spectrally distinguishable substates may have different functional roles.
Journal: Biophysical Chemistry - Volume 147, Issues 1â2, March 2010, Pages 8-12