Fluorescence of tyrosine residues in the basic trypsin inhibitor from bovine lungs

Fluorescence of 0.02 - 2% water solutions of basic trypsin inhibitor in the temperature range of 5 - 80 degrees C at pH 2.6 and 7.7 has been investigated and changes of the relative emission at 302.5 and 307.5 nm analysed. The observed fluorescent effects were ascribed to individual tyrosine residues in the protein molecule. The temperature-dependent changes of spectra were discussed in terms of possible influence of molecular aggregation in solution at higher protein concentrations.