Correlation of proline, hydroxyproline and serine content, denaturation temperature and circular dichroism analysis of type I collagen with the physiological temperature of marine teleosts

Fish products are a promising source of collagen; however, these extracts are biochemically unstable. Acid-soluble collagen (ASC) was isolated from the skin of eleven fish species at various physiological temperatures (T-p). Structural features of these samples were analysed in detail using Circular Dichroism (CD) and compared to their biochemical characteristics. Positive correlation (r = 0.74, p < 0.01) between the T-p and ratio of positive peak intensity to negative peak intensity (R-pn) in CD analysis suggested a higher thermal stability of ASC from warm-water fish, owing to a higher content of cyclic imino acids, such as proline and hydroxyproline (Hyp). Conversely, cold-water fish ASCs contain significantly higher levels of acyclic, hydroxyl groups carrying Ser. These results indicated that CD spectrum techniques including R-pn measurement are concise and helpful for direct detection of the triple helix structure of fish collagens, and that this structure is tightly linked to thermostability of this molecule.