Effect of Glycerol and PVA on the Conformation of Photosystem I

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• 作者：Martin Hussels ; Marc Brecht
• 刊名：Biochemistry
• 出版年：2011
• 出版时间：May 10, 2011
• 年：2011
• 卷：50
• 期：18
• 页码：3628-3637
• 全文大小：994K
• 年卷期：v.50,no.18(May 10, 2011)
• ISSN：1520-4995

文摘

Single-molecule spectroscopy at cryogenic temperatures was used to examine the impact of buffer solution, glycerol/buffer mixtures (25% and 66%), and poly(vinyl alcohol) (PVA) films on the conformation of photosystem I (PSI) from Thermosynechoccocus elongatus. PSI holds a number of chromophores embedded at different places within the protein complex that show distinguishable fluorescence at low temperatures. The fluorescence emission from individual complexes shows inter- and intracomplex heterogeneity depending on the solution wherein PSI was dissolved. Statistical evaluation of spectra of a large number of complexes shows that the fluorescence emission of some of these chromophores can be used as sensors for their local nanoenvironment and some as probe for the conformation of the whole protein complex. Preparation in glycerol/buffer mixtures yields a high homogeneity for all chromophores, indicating a more compact protein conformation with less structural variability. In buffer solution a distinct heterogeneity of the chromophores is observed. PSI complexes in PVA show highly heterogeneous spectra as well as a remarkable blue shift of the fluorescence emission, indicating a destabilization of the protein complex. Photosystem I prepared in PVA cannot be considered fully functional, and conclusions drawn from experiments with PSI in PVA films are of questionable value.