Long-wavelength fluorescence of tyrosine and tryptophan solutions.

We report in this paper the presence of fluorescence bands of tryptophan and tyrosine solutions centered above 550 nm. This long-wavelength fluorescence is of much lower intensity, (0.4-2.7)%, than the UV fluorescence of these aromatic aminoacids. The basic characteristic of these fluorescence bands are: (a) tyrosine: lambda em = 600 nm with two excitation peaks centered at 453 nm and 550 nm (b) tryptophan: lambda em = 675 nm with two excitation peaks centered at 455 and 560 nm. It has been found that irradiation of tyrosine solutions with a potent UV lamp promotes an important increase of absorption at 310 nm and above 400 nm.