Photochemically generated reactive oxygen species (ROS) may play a role in the fate of dissolved organic nitrogen (DON) components. Studies have shown that several dissolved free amino acids are photodegraded by ROS in natural waters, where reaction with singlet oxygen (1O2) was involved in the degradation of these residues. The role of 1O2�mediated degradation of DCAAs, of which protein represents a large fraction of these DON components, is not yet known.  The hypothesis that photolabile amino acid residues have differential susceptibilities to 1O2 activation based on their location within an intact, three-dimensional protein was investigated. In this study, model proteins with well-defined sequences and quaternary protein structures were exposed to 1O2 and photochemical reaction rate constants of individual photolabile residues within the combined form were examined. The results of these studies have implications towards understanding the dynamics and microbial utilization of DON substrates in natural waters.

Indirect photodegradation of dissolved combined amino acids (DCAAs): Reaction of singlet oxygen with model proteins

242nd National Meeting (2011)

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