Techniques for measuring fluorescence and phosphorescence of biological materials

Kinetics of precursor cleavage at the dibasic sites. Involvement of peptide dynamics

The presence in the P'1 position relative to the LysArg doublet of either Phe, Tyr or Trp residues affects only pro-OT/Np(7-15) flexibility. This has a measurable effect on the dynamics of the peptide. Since the same modifications have a major influence on the K(m) and V(max) values of the peptide cleavage, these kinetic parameters should depend on the peptide substrate motions. Therefore, the primary kinetic contribution of substrate cleavage should arise from substrate dynamics rather than from the enzyme.

Triplet-triplet energy transfer in alpha-trypsin

Experiments are reported that demonstrate that light absorbed by ionized tyrosinyl sensitizes the phosphorescence of tryptophanyl residues of native alpha-trypsin. The sensitization effect is abolished when alpha-trypsin is unfolded in guanidine hydrochloride. Under the experimental conditions used, the tryptophan phosphorescence could only have been induced by an electron-exchange interaction. These results, therefore, require that there be at least one ionized tyrosinyl-tryptophanyl pair in the native enzyme and that the distance between the two side chains be sufficiently short to permit electron exchange.

The role of a tyrosyl residue in the mechanism of action of carboxypeptidase B: luminescence studies

The luminescence spectra of carboxypeptidase B indicate specific differences between the zinc and apoenzyme due to the state of tyrosyl residues presumably at the active site. These differences disappear when enzyme-substrate or enzyme-inhibitor complexes are formed, suggesting that they may reflect the interaction of a tyrosyl residue in the native enzyme with the catalytically essential zinc atom. An interpretation of the role of that tyrosyl residue in the mechanism of action of carboxypeptidase B is presented.