Photochemistry of Proteins

Protect from Light: Photodegradation and Protein Biologics

“…The major photolytic pathways of Trp in proteins are shown in Figure 1 and were assembled from articles by Bent and Hayon,5 Davies and Truscott,7 Creed,2 Grossweiner,8 and Laustriat and Hasselmann 9. Following absorption of light the excited state Trp will either relax to the lowest energy singlet state followed by fluorescence, undergo intersystem crossing to the triplet state ( 3 Trp), or eject an electron with formation of a Trp radical cation that will rapidly deprotonate to form the neutral indolyl radical.…”

“…The major photolytic pathways of Tyr in proteins are shown in Figure 2 and were assembled from articles by Bent and Hayon,4 Creed,3 Laustriat and Hasselmann,9 Grossweiner,8 and Davies and Truscott 7. Following absorption of light and excitation to an excited singlet state, a number of processes can occur similar to those for Trp including relaxation by fluorescence from the S1 state to the ground state, relaxation by nonradiative processes to the ground state, and triplet state formation ( 3 Tyr).…”

“…Assemblages of their degradative pathways following absorption of light that are relevant to protein photodegradation are described in Figures 1–4 and will be described in brief here. The intent of this article is not to review primary references, but rather provide descriptions of the pathways assembled from review articles and books 1–9. Primary or Type I photodegradation begins with absorption of light resulting in excitation of an electron to higher energy singlet states.…”

“… Structure of cystine and common photolytic pathways. Pathways were assembled from articles by Hoffman and Hayon,25 Creed,1 Laustriat and Hasselmann,9 Grossweiner,8 and Davies and Truscott 7…”

Recent Developments in Singlet Molecular Oxygen Chemistry

“…(A Yearly Review on photooxidation of proteins has appeared [43].) With 50 S ribosomal protein it was found that the protein B-L3 has one or more histidine residues which are essential for its peptidyl-transferase and subunit association activity [25].…”