The Reaction of Singlet Oxygen With Proteins, With Special Reference to Crystallins

Abstract

Photosensitized oxidation of the eye lens proteins, the crystallins, is thought to lead to protein crosslinks and high molecular weight aggregates. Such protein modifications may be important factors in the formation of lens opacities or cataracts. We focus attention here on type 2 photo-oxidation involving the reaction of singlet oxygen (1O2) with crystallins and some "control" proteins. We find that: (1) trp residues are oxidized to N-formyl kynurenine and related products, but this in itself does not lead to the production of high molecular weight protein aggregates of the protein; (2) tyr residues react with 1O2 but we do not detect dihydroxyphenylalanine or bityrosine nor are protein crosslinks formed as a result; (3) oxidation of his residues appears necessary for high molecular weight protein covalent aggregates to form. Proteins devoid of his, e.g. melittin or bovine pancreatic trypsin inhibitor, do not form high molecular weight products upon reaction with 1O2. Prior reaction and blocking of his inhibits the crosslinking reactions. (4) The oxidized protein is seen to be more acidic than the parent and has an altered tertiary structure. (5) Among the crystallins, reactivity towards 1O2 varies in the order gamma greater than beta greater than alpha and also gamma A/E greater than gamma D greater than gamma B crystallin.

Photoinduced modifications by fluoroquinolone drugs in bovine serum albumin (BSA) and ribonuclease A (RNAse) as model proteins

“…Solutions of Bovine serum albumin (BSA) (0.5 mg/ml) in phosphate buffer 10 mM were irradiated in the presence of the test compounds for various times in a quartz cuvette. At each time the Tryptophan (Trp) content was followed by monitoring the characteristic Trp fluorescence as described by Balasubramanian et al, 20 . Solutions of Ribonuclease A (RNAseA), 0.5 mg/ml in phosphate buffer 10 mM were irradiated in the presence of the test compounds for various times in a quartz cuvette.…”

“…The Trp content was directly analyzed by monitoring the characteristic fluorescence of Trp residues in BSA 20 . As depicted in Figure 9, a rapid decrease of the fluorescence was observed under aerobic condition for CPX and NOR.…”

Photochemical crosslinking of collagen and Poly (vinyl pyrrolidone) hydrogel system for biomedical applications by using novel photo initiators

“…Collagen and PVP are completely miscible and interacts with each other by formation of inter and intra molecular hydrogen bonding [12]. This can be best achieved by photo polymerization which mainly involves exposure to light in presence of photo reactive species to generate free radicals which in turn helps in the formation of bonding in the hydrogels [13] [14].…”

Review: In vivo and postmortem effects of feed antioxidants in livestock: a review of the implications on authorization of antioxidant feed additives

“…These include HPLC and ELISA procedures (Griffiths, 2000;Han et al, 2000). However, many of these methods have been criticized for being unreliable and non-specific, coupled with the controversial debate of whether or not carbonyls represent good markers of protein oxidation in vivo (Balasubramanian et al, 1990;Stadtman and Oliver, 1991;Stadtman and Berlett, 1997). …”