Comparative Photoactivity and Stability of Isolated Cyanobacterial Monomeric and Trimeric Photosystem I

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• 作者：David R. Baker ; Amy K. Manocchi ; Melissa L. Lamicq ; Meng Li ; Khoa Nguyen ; James J. Sumner ; Barry D. Bruce ; Cynthia A. Lundgren
• 刊名：Journal of Physical Chemistry B
• 出版年：2014
• 出版时间：March 13, 2014
• 年：2014
• 卷：118
• 期：10
• 页码：2703-2711
• 全文大小：434K
• 年卷期：v.118,no.10(March 13, 2014)
• ISSN：1520-5207

文摘

Photoactivity of native trimeric, and non-native monomeric Photosystem I (PSI) extracted from Thermosynechococcus elongatus is compared in a photoelectrochemical system. The PSI monomer is isolated by disassembling a purified PSI trimer using a freeze鈥搕haw technique in presence of the short-chain surfactant, octylthioglucoside. Photoactive electrodes are constructed with PSI, functioning as both light absorber and charge-separator, embedded within a conductive polymer film. Despite structural differences between PSI trimers and monomers, electrodes cast with equal chlorophyll-a concentration generate similar photoactivities. Photoaction spectra show that all photocurrent derived from electrodes of PSI and conductive polymer originates solely from PSI with no photocurrent caused by redox mediators in the conductive polymer film. Longevity studies show that the two forms of PSI photodegrade at the same rate while exposed to equal intensities of 676 nm light. Direct photo-oxidation measurements indicate that PSI鈥檚 monomeric form has fewer light harvesting antennae than trimer, and also shows energy sharing between monomeric subunits in the trimer. The structure of PSI is also found to impact cell performance when applying light at incident powers above 1.5 mW/cm² due to the reduced optical cross-section in the monomer, causing saturation at lower light intensities than the trimer.