Mechanistic studies of photochemical protein modification using 1,8-naphthalimides.

Certain 4-alkylamino-1,8-naphthalimides have been used as photosensitizers for photochemical protein crosslinking. In my research various types of 4-amino and N-substituents naphthalimides have been synthesized and studied for application to protein crosslinking and tissue bonding. Ribonuclease A (RNase A) was used as a model protein in the protein for crosslinking studies. The photochemical crosslinking experiments were analyzed using SDS-PAGE electrophoresis and western blot detection. Biotinylated naphthalimides were also synthesized and it was demonstrated that while they could catalyze photochemical protein crosslinking, they were not incorporated into the crosslinked proteins. It was shown previously that tyrosine and histidine residues were involved in protein crosslinking through type I and type II mechanisms. Therefore, suspect amino acids such as tyramine, tryptamine, L-tryptophan, and dopamine were combined with biotin in order to allow us to detect their incorporation into the photooxidized protein. It was also shown that the biotin-tyramine compound and biotin-LC-hydrazide can serve as inhibitors of photochemical protein crosslinking. These studies serve to allow us to better understand mechanism of photochemical protein crosslinking.