Physico-chemical characterisation and molecular organisation of the collagen from the skin of an air-breathing fish (Ophiocephalus striatus)

Collagen has been prepared from the skin of an air-breathing Indian fish(Ophiocephalus striatus) by extraction with cold 0.5M acetic acid and purification by alternate precipitation with NaCl and dialysis against 0.02M Na₂HPO₄. The purified collagen was characterised with respect to physico-chemical properties, amino acid composition and chromatography of the denatured collagen. The fish collagen has a higher shrinkage temperature and denaturation temperature compared to that of the allied teleosts living in exclusively aquatic medium. These differences could possibly be reflections of the response to the rigours of the environment. As found for other vertebrate collagens, the fish collagen contains two kinds of single chains the α₁ and α₂ chains as revealed by sodium dodecyl sulphate-polyacrylamidegel electrophoresis and carboxymethylcellulose chromatography.     

The possible relevance of autoxidative glycosylation in glucose mediated alterations of proteins: An in vitro study on myofibrillar proteins

The present work was carried out to examine the role of glycation and transition metal catalysed autoxidation of sugars in glucose-mediated alterations of myofibrillar proteins. Myofibrils were prepared from rat skeletal muscle and incubated with 1) sugar alone 2) sugar and micromolar concentrations of transition metals (Cu²⁺ or Fe³⁺) 3) transition metals alone and the control remained without sugar or transition metals. A significant increase in extent of glycation and decrease in ATPase activity of myofibrils incubated under autoxidative conditions were observed over the other three incubations. Reducing agent 2-mercaptoethanol was highly effective in preventing the alterations induced by glucoxidation, compared to EDTA and aminoguanidine, suggesting the involvement of thiol group oxidation in the reduced function of the protein. Free radical scavengers like catalase, benzoic acid and mannitol were also effective in preventing glucose mediated alterations. Although a high concentration of glucose alone has an insignificant effect on myofibrils in vitro, the results from the present work suggest that glucose in combination with transition metals could lead to functional alterations of myofibrils, and this process by generating free radicals may contribute to the overall complications of diabetes and aging.