Globular proteins chromophores

An essential element in this program is the preparation of pure protein derivatives site specifically labeled by a donor and acceptor and their characterization. Several methods were developed for speci-fic labeling of globular proteins and applied in the preparation of fluorescent derivatives of bovine pancreatic trypsin inhibitor (BPTI) and ribonuclease (RNase). Methoxy-naphthyl derivatives are used as donor chromophores, in particular 2-methoxy-1-naphthyl-methylenyl (MNA) and 2-naphthoxy-acetyl (NAA) were used as donor chromophores (Fig. 3). These two probes are characterized by spectral characteristics suitable for measurements by the present methods (Fig. 4). In particular,they both show monoexponential decay when attached to the protein in the absence of an acceptor under all experimental conditions tested so far. This is a key element in the analysis of fluorescence decay curves of donor-acceptor labeled derivatives, in which all deviations from monoexponential decay are interpreted as distributions of distance. 7-dimethylamino-coumarine-4-acetyl (DA-coum) or 2,4-dinitrophenyl residues were used as acceptors. 

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