A partial characterization of the major fluorophore of bovine ligamentum elastin

Several chemical methods were used to partially characterize the structure of the major fluorophore of bovine ligament elastin. The fluorophore was not soluble in ether and, therefore, is not a lipid. Based on the spectra of the fluorophore when dissolved in water-saturated n-butanol and the lack of an ionization effect on the fluorescence between pH 2 and 10, it is concluded that the fluorophore has neutral charge in this pH range. Below pH 2, changes noted in fluorescence most likely reflected protonation of the fluorophore. No derivatization occurred with phenylisothiocyanate, o-phthaladehyde or carbodiimide, indicating that the fluorophore is unlikely to be an amino acid. Fluorescence was diminished by strong acid, alkali and ultraviolet irradiation. It is concluded that the fluorophore is a nitrogen-heterocyclic compound distinct from previously reported elastin fluorophores. The precursor for this compound is not apparent, though it appears to be exogenous to elastin.