Effect of Visible Light on Amino Acids—i. Tryptophan

Abstract

Abstract— Seven chromatographically separable products were shown to be formed when an aqueous solution of tryptophan was exposed to the light of a 100‐W bulb at pH 9 in the presence of methylene blue and oxygen. Some of these products were detected, though in much smaller quantities, even when tryptophan was irradiated in the absence of methylene blue and/or oxygen. Contrary to reports in the literature, none of the common derivatives of tryptophan, such as tryptamine, indole acetic acid, indole aldehyde, anthranilic acid or kynurenine, were detected on irradiation of the amino acid by visible light. Such irradiation of tryptamine and indole acetic acid gave 1–2 components which were chromatographically identical with those obtained from tryptophan; irradiation of indole aldehyde gave no detectable breakdown products. Exposure of tryptophan to ultraviolet light or when treated with hydrogen peroxide did not result in the formation of any of the products obtained with visible light. The results presented here suggest that during exposure of tryptophan to visible light, the indole ring is first oxygenated resulting in the formation of dioxindole derivatives. One of the products of irradiation of tryptophan with visible light was tentatively identified as dioxin‐dolylalanine.

Crosslink formation in porcine valves stabilized by dye-mediated photooxidation

“…Work is planned to determine the number and kinds of unique crosslinks formed as a result of photooxidation, the chemical structure of these species, and whether these crosslinks are intermolecular. Data have been previously presented supporting crosslinking by the photooxidation process,14, 23 and specifically, formation of intermolecular, zero‐length crosslinks as a result of photooxidation have been described 24, 25. Crosslinking by this mechanism may have advantages over typical glutaraldehyde crosslinking, which introduces polyfunctional structures linking the free amine groups of the collagen molecule.…”

Calcification resistance, biostability, and low immunogenic potential of porcine heart valves modified by dye-mediated photooxidation

“…[37][38][39][40][41][42][43][44][45] Previously, photooxidation was used to study protein function through amino acid alterations. [46][47][48][49][50][51][52][53][54][55][56] The discovery that photooxidation could stabilize a protein solution 56 led to the development of this technology for biomedical purposes. The process was found to yield a biomaterial possessing many favorable properties for long-term implantable medical devices.…”

Visible Light Degradation of a Monoclonal Antibody in a High-Concentration Formulation: Characterization of a Tryptophan-Derived Chromophoric Photo-product by Comparison to Photo-degradation of N-Acetyl-l-tryptophan Amide

“…Hence, there is a finite possibility for Trp photochemistry around 400 nm. Importantly, Gurnani et al 48 observed photo-degradation of Trp by visible light in the absence of photosensitizers. In addition, the photo-degradation of pharmaceutical proteins by visible light was reported in various publications.…”