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1.
Photochem Photobiol ; 87(5): 1050-7, 2011.
Artigo em Inglês | MEDLINE | ID: mdl-21668872

RESUMO

A prerequisite for any "lab on a chip" device that utilizes an electrical signal from the sensor protein is the ability to attach the protein in a specific orientation onto a conducting substrate. Here, we demonstrate the covalent attachment to a gold surface of light-harvesting membrane proteins, from Rhodobacter sphaeroides, via cysteine (Cys) residues engineered on either the cytoplasmic or periplasmic face. This simple directed attachment is superior in its ability to retain light-harvesting complex (LHC) function, when compared to a similar attachment procedure utilizing a self-assembled monolayer on gold. LH 1 has previously been observed to have superior photostability over LH 2 (Magis et al. [2010] Biochim. Biophys. Acta, 1798, 637-645); this characteristic is maintained even with the introduction of Cys residues.


Assuntos
Proteínas de Bactérias/química , Cisteína/química , Dispositivos Lab-On-A-Chip , Complexos de Proteínas Captadores de Luz/química , Proteínas de Membrana/química , Rhodobacter sphaeroides/química , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Cisteína/metabolismo , Ouro/química , Luz , Complexos de Proteínas Captadores de Luz/genética , Complexos de Proteínas Captadores de Luz/metabolismo , Proteínas de Membrana/genética , Proteínas de Membrana/metabolismo , Microscopia de Força Atômica , Mutagênese Sítio-Dirigida , Processos Fotoquímicos/efeitos da radiação , Ligação Proteica
2.
Biochim Biophys Acta ; 1798(3): 637-45, 2010 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-20036635

RESUMO

Photosynthetic membranes comprise a network of light harvesting and reaction center pigment-protein complexes responsible for the primary photoconversion reactions: light absorption, energy transfer and electron cycling. The structural organization of membranes of the purple bacterial species Rb. sphaeroides has been elucidated in most detail by means of polarized light spectroscopy and atomic force microscopy. Here we report a functional characterization of native and untreated membranes of the same species adsorbed onto a gold surface. Employing fluorescence confocal spectroscopy and light-induced electrochemistry we show that adsorbed membranes maintain their energy and electron transferring functionality. Gold-adsorbed membranes are shown to generate a steady high photocurrent of 10 microA/cm(2) for several minutes and to maintain activity for up to three days while continuously illuminated. The surface-adsorbed membranes exhibit a remarkable functionality under aerobic conditions, even when exposed to light intensities well above that of direct solar irradiation. The component at the interface of light harvesting and electron cycling, the LH1 complex, displays exceptional stability, likely contributing to the robustness of the membranes. Peripheral light harvesting LH2 complexes show a light intensity dependent decoupling from photoconversion. LH2 can act as a reversible switch at low-light, an increased emitter at medium light and photobleaches at high light.


Assuntos
Membrana Celular/efeitos da radiação , Transferência de Energia/efeitos da radiação , Ouro/química , Luz , Fotossíntese/fisiologia , Rhodobacter sphaeroides/citologia , Adsorção/efeitos da radiação , Membrana Celular/ultraestrutura , Eletrodos , Transporte de Elétrons/efeitos da radiação , Complexos de Proteínas Captadores de Luz/metabolismo , Microscopia de Força Atômica , Rhodobacter sphaeroides/efeitos da radiação , Soluções , Espectrometria de Fluorescência , Propriedades de Superfície/efeitos da radiação
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