Streptavidin-Phycoerythrin Conjugated Proteins Bound to Biotin on Langmuir-Blodgett Films of Biotinylated Lipid Monolaye
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STREPTAVIDIN-PHYCOERYTHRIN CONJUGATED PROTEINS BOUND TO BIOTIN ON LANGMUIR-BLODGETT FILMS OF BIOTINYLATED LIPID MONOLAYERS LYNNE A. SAMUELSON*, D.L. KAPLAN, K.A. MARX--, P. MILLER--, D.M. GALOTTI**, J. KUMAR", AND S.K. TRIPATHY** *U.S. Army Natick Laboratories, Biotechnology Branch, Natick, MA 01760 "*University of Lowell, Departments of Chemistry and Physics, Lowell, MA 01854 ABSTRACT Studies involving the specific and non-specific surface recognition of biotin on biotinylated LB lipid monolayers by streptavidin and avidin conjugated phycoerythrin are presented. Both streptavidin and avidin conjugates were injected under the monolayer and found to preferentially adsorb to the biotinylated monolayers at the air-water interface. Pressure-area isotherms displayed a biotin-streptavidin/avidin complex dependent increase in surface pressure at expanded areas indicating protein adsorption. The binding of protein was confirmed by transferring the monolayer films to solid supports and measuring the characteristic intense phycoerythrin fluorescence at 576 nm. The effect of protein charge, monolayer packing density and structure, and activation of the tetramer proteins towards specific and non-specific binding are discussed. These results suggest a novel and general methodology for the two-dimensional ordering of protein monolayers with potential bioelectronic, optical and protein structure research applications. INTRODUCTION The Langmuir-Blodgett technique has been used extensively in the past as a method to simultaneously orient and couple various organic surfactant materials to electronic and optical substrates for an extensive number of molecular device applications. Recently, there has been a great interest in extending this methodology to incorporate biological materials into these assemblies. The end purpose is to elicit the desired inherent, intelligent materials properties which nature has evolved and fine-tune them to serve in many biomedical research and biotechnology applications. In addition, such integrated assemblies should simultaneously provide unique biomimetic or simple environments for the study of protein structure. One such example may include crystallographic TEM structure studies on ordered two-dimensional protein crystals where the two-dimensional or large three-dimensional protein crystals are difficult to obtain [1]. This research, therefore, involves the development of a novel methodology which incorporates and couples a photodynamic, water soluble protein, phycoerythrin, into biomimetic monolayer films via the Langmuir-Blodgett technique. Phycoerythrin is the outer most phycobiliprotein of the phycobilisome "Light Harvesting System" found in red algae [2,3]. These are highly pigmented proteins that exist as well organized geometrical discs or rods, which in this arrangement, serve to extend the narrow visible range absorption of chlorophyll to longer wavelengths by channeling ambient light through a nonradioactive energy transfer process to Photosystem II with very high quantum efficiencies [4].
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