Fluorescence Properties of Fluorescamine-Protein Conjugates

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Abstract
Fluorescamine reacts rapidly with proteins to produce conjugates having A light blue fluorescence. The quantum yields of various conjugates were found to differ significantly, and the measured lifetimes at 25° ranged from 6 to 9 nsec. The yields were highly temperature-dependent. Fluorescence polarization datA show energy transfer between fluorescamine moieties in albumin conjugates. Rotational relaxation times determined from depolarization measurements in good agreement with values reported in studies of proteins labeled with conventional dyes. In water, the fluorescamine derivates of amino acids have lower quantum yields and lifetimes than found in protein conjugates. A blue shift and an increase in quantum yield accompany reduction of solvent polarity, but the spectral shift is quite small. The implications of these datA for the assay of protein amino groups and for protein studies are discussed.