Charge transfer between fluorescein and tryptophan as a possible interaction in the binding of fluorescein to anti-fluorescein antibody.
Steady-state and time-resolved fluorescence studies of fluorescein (Fl) and 9-hydroxyphenylfluoron (HPF) bound to high-affinity rabbit anti-Fl IgG antibody (anti-Fl IgG) have been performed. The heterogeneity in the fluorescence properties observed for Fl bound to anti-Fl IgG is reduced for HPF bound to anti-Fl IgG. A charge transfer between a tryptophyl residue in the binding site and the hapten was considered as a possible binding interaction. Fl was observed to form complexes in solution with the amino acids tryptophan, tyrosine and methionine, probably due to charge transfer. Also, the fluorescence of tryptophyl residues of the protein is quenched on binding. While such charge transfer complexes may be present, there is no direct evidence that charge transfer complexes between Fl and tryptophan are necessarily present for Fl bound to all high-affinity anti-Fl IgG molecules.
D000596:Amino Acids / Q000378:metabolism; D000937:Antigen-Antibody Reactions; D019793:Fluorescein; D005452:Fluoresceins / Q000276:immunology / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007074:Immunoglobulin G / Q000378:metabolism; D013050:Spectrometry, Fluorescence; D013696:Temperature; D014364:Tryptophan / Q000378:metabolism*
D000596:Amino Acids; D005452:Fluoresceins; D007074:Immunoglobulin G; C044729:9-hydroxyphenylfluoron; D014364:Tryptophan; D019793:Fluorescein