We report herein on the development of a FRET-based method to detect changes caused by viral protein-receptor binding. FRET fluorophore pairs (donor and acceptor fluorophores) were tagged to two specific receptors, both which bind to a viral protein. When the binding event occurs, the distance between the donor and acceptor FRET fluorophores is decreased, thus initiating the fluorescence resonance energy transfer (FRET). Since the binding event is unique to the viral protein, fluorescent change indicates the present of the virus. In this paper, the viral protein gp120, which is the featured protein on the surface of HIV-1, was detected. The receptors, CD4 and gp120-antibody which specifically bind to gp120, were conjugated to the FRET fluorophore pair, AMCA-NHS (succinimidyl-7-amino-4-methylcoumarin-3-acetic acid) and FITC (fluorescein isothiocyanate) respectively. Spectrofluorimetry was used to detect the fluorescent change between AMCA-NHS and FITC peak intensities when the receptors bind to the gp120. Specific binding gp120 and non-specific binding gp120 were used to test the selectivity of the sensor. The results indicated that FRET-conjugated receptors can efficiently detect the presence of gp120.
We report herein on the development of a dual receptor detection method for enhanced biosensor monitoring. The proposed scheme requires the integration of a chemical transducer system with two unique protein receptors that bind to a single biological agent. Optical transduction occurs because the two protein receptors are tagged with special molecular groups. When bound to a single biological agent, these fluorescently labeled proteins undergo a change in fluorescence. This `fluorescent switching' relies on the well-known mechanisms of fluorescent resonance energy transfer (FRET). The paper focuses on the investigation and optimization of the chemical transduction system (FRET). A number of FRET dye pairs were tested in a spectrofluorimeter, and promising FRET pairs (FITC/TRITC and DMACA/FITC) were further tagged to the protein, avidin and its ligand, biotin. Due to their affinities, the FRET-tagged biomolecules combine in solution, resulting in a stable, fluorescent signal from the acceptor FRET dye with a simultaneous decrease in fluorescent signal from the donor FRET dye. The results indicate that the determined FRET pairs can be utilized in the development of dual receptor sensors.
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