| The capability of photochemical crosslinking of proteins and collagen by 1, 8-naphthalimides compounds was assessed and investigated by electrophoresis, autoradiography, collagenase digestion, scanning electron microscopy and transmission electron microscopy. Electrophoretic results show that 1, 8-naphthalimide can: (1) crosslink monomeric protein bovine ribonuclease A into dimer, trimer, tetramer and other higher-molecular-weight crosslinking products; (2) crosslink heterogeneous protein mixture of enzymes secreted by Clostridium histolyticum into high-molecular-weight products which appeared in the stacking gel and (3) crosslink soluble collagen into high-molecular-weight products and form aggregates with concomitant decreasing amounts of alpha and beta components of collagen after laser irradiation. Photochemical crosslinking proteins and collagen by naphthalimide may not involve Cys, Trp or His-His linkage, and glycoprotein is not required for this reaction. Autoradiography showed naphthalimide is incorporated into the crosslinked products. Collagen photochemically crosslinked by 1, 8-naphthahmide changes the sequential digestion pattern of collagenase. Scanning electron micrographs showed that collagen fibrils, extracted from bovine Achilles tendon, became looped, contorted and folded into "flower-like" and "flake-like" structures after photochemical crosslinking by 1, 8-naphthalimide, indicative of inter-fibrillar crosslinking. Transmission electron micrographs showed fusion of collagen fibrils, in the rat tail tendon tissues after photochemical crosslinking by 1, 8-naphthalimide, which also indicates inter-fibrillar crosslinking. Photochemical crosslinking of collagen may have many potential medical applications. Further investigation in the mechanism of photochemical crosslinking by 1, 8-naphthalimide and further evaluation in cytotoxicity of 1, 8-naphthalimide will be undertaken in the future. |
