Energy Transfer Studies between Trp Residues of Three Lipocalin Proteins Family, α1-Acid Glycoprotein, (Orosomucoid), β-Lactoglobulin and Porcine Odorant Binding Protein and the Fluorescent Probe, 1-Aminoanthracene (1-AMA)

Energy transfer studies between Trp residues of alpha(1)-acid glycoprotein, beta-lactoglobulin and porcine odorant binding protein (OBP) and the fluorescent probe 1-aminoanthracene (1-AMA) were performed. 1-AMA binds to the hydrophobic binding sites of the three proteins inducing a decrease in the fluorescence intensity of the Trp residues accompanied by an increase of that of 1-AMA. Our results indicate that 1-AMA is in close contact with hydrophobic tryptophan residue of beta-lactoglobulin (Trp 19) to the difference of its binding to OBP, where Trp residues are far from the pocket and to alpha(1)-acid glycoprotein where three Trp residues are present at different areas of the protein.