A collagen-associated Ehrlich chromogen: a pyrrolic cross-link?

Abstract

P r o t e i n a s e d iges t s of c o l l a g e n r i c h t i s sues (bone, tendon, skin, cartilage, periosteum) give a pink colour with dimethylaminobenzaldehyde in acid solution. The chromogen is associated with polymeric collagen, but is a b s e n t f rom n e u t r a l s a l t s o l u b l e co l lagen . It is suggested that amino-ketone forms of collagen crosslinks undergo in vivo a spontaneous Knorr condensation with each other) or with other species, to produce a pyrrolic cross-link.