Studies on the tyrosine environment of flammulin

By the UV difference spectrum acid fluorescence spectrum technique, the tyr osine environment of flammulin was studied and the results show a typical m aximal UV absorption peak of tyrosine residues in flammulin at 275nm, with epsilon(max) = 20322 L.mol(-1).cm(-1). According to the results of the UV d ifference spectrophotometric titration, the UV difference absorption Delta A(294.4nm) shows close correlation to pH ranging from 10.1 to 12.5. The tit ration curve of tyrosine shows that the apparent dissociation constant pK(a )' of tyrosine is 11.4. Since no tryptophane is found in flammulin, the pro tein only shows the fluorescence of tyrosine residues. The fluorescence spe ctrum of flammulin shows that the maximal emission wavelength is at 305nm w hen excited at 280nm, which is sensitive to SDS and pH and quenchable by ac rylamide but not by KI. The results indicate that the tyrosine residues of flammulin reside in the hydrophobic core, and the tyrosine residues, togeth er with other hydrophobic amino acid residues in flammulin, form a stable n on-polar hydrophobic environment.