Hydroxyproline and the Shrinkage Temperature of Collagen

Abstract

IT is well known that collagens from various sources have characteristic shrinkage temperatures (T _s), at which samples will contract abruptly in water or in 0.9 per cent saline solution. The T _s values of fish-skin collagens range from about 35° C. to 57° C., according to the mean temperature of the environment¹, while mammalian collagen has a T _s value of about 62° C., apparently irrespective of source. By an examination of the complete amino-acid analyses, these shrinkage temperatures have been correlated with the hydroxyproline content of the collagen; the lower the amount of hydroxyproline the lower the value of T _s (ref. 1). Hydroxyproline is considered to consolidate the collagen structure by forming hydrogen bonds between molecular chains. The data of ref. 1 have been plotted by us in Fig. 1 using the mean values of the shrinkage temperature quoted. These data are represented by circles and include the additional values, hydroxyproline = 12.0 per cent and 13.0 per cent for cattle hide and rat tail tendon respectively. The continuous straight line in Fig. 1 has been fitted by the method of least squares to these data on the assumption that the relation between hydroxyproline and T _s is linear.