CHEMICAL AND PHYSICAL BEHAVIOUR OF COLLAGEN FIBRE IN ALKALINE SOLUTIONS

The chemical and physical behaviour of skin collagen fibre was studied in alkali solutions. After treatment with sodium hydroxide and calcium hydroxide solutions, the characteristic D-period of collagen fibril could not be seen by TEM. The fibril diameter increased by swelling in alkali solutions. The swelling occurred both inter and intra fibrils. The hydrolysate of collagen in alkali solution was seen as a flat structure which illustrated that the hydrolysate was denatured in alkaline solutions. When collagen fibre was treated in alkali solutions for long periods, the isoelectric points of collagen hydrolysate were between 4.5 and 5.0. The higher the concentration of alkali solution, the lower the isoeletric point of the hydrolysate. During alkali treatments, the isoelectric point shifted to lower pH and, after 48 hour treatment, the isoelectric point reached equilibrium and did not change further. The triple helix conformation of collagen was destroyed when collagen was hydrolyzed in solutions of alkali according to the CD spectrum. SDS-PAGE electrophoresis results showed that hydrolysate of collagen in alkali solutions presented as a continuous band, no characteristic band of collagen appeared. The hydrolysis of collagen fibre in alkali solutions not only happened at inter-molecular points, but also happened at peptide bonds of collagen molecule which was randomly hydrolysed.