Covalent Attachment of Bacteriorhodopsin Monolayer to Bromo‐terminated Solid Supports: Preparation,Characterization, and Protein Stability |
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Authors: | Yongdong Jin Dr Olga Girshevitz Dr Noga Friedman Dr Izhar Ron David Cahen Prof Mordechai Sheves Prof |
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Institution: | 1. Department of Organic Chemistry, Weizmann Institute of Science, Rehovot 76100 (Israel), Fax: (+972)?8‐934‐4142;2. Department of Chemistry, Bar‐Ilan University, Ramat Gan 52900 (Israel);3. Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot 76100 (Israel) |
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Abstract: | The interfacing of functional proteins with solid supports and the study of related protein‐adsorption behavior are promising and important for potential device applications. In this study, we describe the preparation of bacteriorhodopsin (bR) monolayers on Br‐terminated solid supports through covalent attachment. The bonding, by chemical reaction of the exposed free amine groups of bR with the pendant Br group of the chemically modified solid surface, was confirmed both by negative AFM results obtained when acetylated bR (instead of native bR) was used as a control and by weak bands observed at around 1610 cm?1 in the FTIR spectrum. The coverage of the resultant bR monolayer was significantly increased by changing the pH of the purple‐membrane suspension from 9.2 to 6.8. Although bR, which is an exceptionally stable protein, showed a pronounced loss of its photoactivity in these bR monolayers, it retained full photoactivity after covalent binding to Br‐terminated alkyls in solution. Several characterization methods, including atomic force microscopy (AFM), contact potential difference (CPD) measurements, and UV/Vis and Fourier transform infrared (FTIR) spectroscopy, verified that these bR monolayers behaved significantly different from native bR. Current–voltage (I–V) measurements (and optical absorption spectroscopy) suggest that the retinal chromophore is probably still present in the protein, whereas the UV/Vis spectrum suggests that it lacks the characteristic covalent protonated Schiff base linkage. This finding sheds light on the unique interactions of biomolecules with solid surfaces and may be significant for the design of protein‐containing device structures. |
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Keywords: | adsorption monolayers photoactivity retinal proteins Schiff bases |
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