Photosensitized Cross-Linking of Tryptophan and Tyrosine Derivatives by Rose Bengal in Aqueous Solutions.

Photosensitized cross-linking of N-acetyl derivatives of tryptophan and tyrosine by rose bengal in phosphate buffer saline was studied by steady-state absorption and emission spectroscopy, nanosecond transient absorption spectroscopy, and chemical analyses. These amino acids undergo cross-linking to form dimeric and higher oligomeric products under anoxic conditions with rose bengal as a sacrificial oxidant, whereas they react predominantly with singlet oxygen produced by rose bengal in aerated solutions. This investigation provides a comprehensive view into the first steps of rose bengal photosensitized cross-linking of these two amino acids. The results can be helpful for future applications of rose bengal and related dyes, such as photochemical tissue bonding or visible light photocatalysis.