Photolysis of crosslinked peptides from elastin of porcine aorta.

Elastin, a fibrous protein found in connective tissue is a hydrophobic, highly crosslinked insoluble protein. The study of its primary structure has been greatly hindered because no specific enzymatic or chemical method is known which would release a finite number of homogeneous peptides. Since the major crosslinks are tetrasubstituted pyridinium compounds, the (iso)desmosines [l] (1, fig.1) we are exploring the possibility of breaking speci~c~y the aromatic ring byphotolysis. The photochemic~ decomposition of free (iso)desmosines has been studied [2] and it was found that the primary photochemical event is the formation of a tetrasubstituted azabicyclo compound 2, which is subsequently hydrolysed to give an open chain aminoaldehyde 3. This compound can either recyclise to give a novel isomer of (iso)desmosines, photodesmosine 5 (in preparation) or be further hydrolysed to give free lysine and a trisubstituted analogue of glutaconic aldehyde 4. In this paper we wish to report on the photochemi~~ behavior of (iso)de~os~es present in highly reticulated peptides obtained by non-specific cleavage of aortic elastin [3].