Fluorescence Measurements and AFM Imaging of Bacteriorhodopsin Coupled with CdSe Quantum Dots for Optoelectronic Applica
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1237-TT10-03
Fluorescence measurements and AFM imaging of Bacteriorhodopsin coupled with CdSe quantum dots for optoelectronic applications Nicolas Bouchonville1, Michael Molinari1, Alyona Sukhanova2,3, Michel Troyon1, and Igor Nabiev2,3 1
LMEN EA3799, Université de Reims Champagne Ardenne, 21, rue Clément Ader, 51685 Reims Cedex 2, France 2
EA3798, Détection et approches thérapeutiques nanotechnologiques dans les mécanismes biologiques de défense, URCA, 51, rue Cognacq-Jay, 51100 Reims, France 3
CIC nanoGUNE Consolider, E-20018 Donostia-San Sebastian, Spain
ABSTRACT A new nanohybrid material with a potential impact on energy transfer processes in biomolecules was developed by coupling colloidal fluorescent semiconductor CdSe/ZnS quantum dots (QDs) with a photochromic membrane protein, the bacteriorhodopsin (bR). The interactions between the nanocrystals and the proteins were studied by fluorescence spectroscopy and atomic force microscopy (AFM) measurements. A quenching in the photoluminescence (PL) of QDs emitting in the range of the bR absorption suggests a fluorescence resonance energy transfer effect from QDs (donors) to bR (acceptor). As the quenching evolution is different with the surface charges of the QDs, it suggests that the QDs interact with bR through electrostatic interactions. The AFM images of bR coupled with QDs capped with positive or negative surface groups confirm that the electrostatic interactions between QDs and bR play a dominant role in the way they are coupling together. The observed interactions between QDs and bR can provide the basis for the development of novel functional materials with unique photonic properties and having applications in the all-optical switching, photovoltaics and data storage.
INTRODUCTION Bioelectronics and biophotonics, which have shown considerable promise, are the subfields of molecular electronics that investigate the use of native as well as modified biological molecules in electronic or photonic devices. Much of the current research effort is directed towards self-assembled monolayers and protein-based photonic devices. Although a number of proteins have been explored for bioelectronics device applications [1,2], bR has received the most attention [3,4]. bR is photochromic integral membrane proteins incorporated within the natural purple membranes (PM) of bacteria Halobacterium salinarum. Upon illumination by light, bR undergo a cyclic sequence of distinguishable photo-intermediates changing absorption in the blue-to-red region of the spectrum [5]. The high quantum efficiency of the initial bR state guarantees an efficient photoisomerization of the protein-linked bR chromophore (retinal) strongly absorbing light and located near to the centre of the PM, at a distance from both PM surfaces of nearly 2.5nm, which is far less than the Förster radius of effective energy transfer [6]. The long-term stability of PM against thermal (up to 140°C), chemical, and photochemical
degradation, high ionic strength and extreme pH values [7] has made bR the most promi
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