Several structural proteins which we have been investigating contain certain fluorescent substances in addition to the normally occurring amino acids. Some of these fluorescent substances are derived from constituent amino acids in the proteins, whereas others are as yet unidentified. In attempting to isolate and characterize the various fluerescent materials, some of which appear to be involved in protein cross-linking, it is necessary tlo distinguish between those occurring naturally and others producecl as artifact's during protein purificat,ion and acid hydrolysis. In t'his and t.he accompanying paper, we have examined the fluorescence of purified amino acids, before and after treatment with acid, and in several highly purified proteins and peptidca. By examining both the fluoresccncc spectra and t'he fluorescence intensity of various subst'ances productbd by the conditions of acid hydrolysis, as well as during separaGon and isolation of the fluorescent moieties, we hope to establish conditions t,hat will permit us to diatinguish between natura,lly occurring and artif act'ually produced compounds.
MATERIALS AXD METHODS
Matetiall. The following compounds were used as purchased from Mann Research Laboratories : glycine, alanin?: valine, leucine, isoleucine, glutamic acid, aspartie acid, threoninc i&o), phenylalanine, tryptophan, '