Extendability of Tendons undergoing Contraction-Relaxation

Abstract

EQUILIBRIUM melting of tendons¹ and collagenous tissues² follows the theoretical behaviour expected for a first-order phase transition. Thus, the ordered crystalline regions of polypeptide chains disintegrate into randomly oriented coils of the amorphous phase. Rat-tail tendons subjected to melting by lyotropic agents undergo rapid contraction followed by relaxation to rupture, and these physical events are easily measured characteristics of the melting process. Stress-strain curves of thermally shrunk tendons have been shown to obey equilibrium elastic theory for amorphous polymers³; for example, stress is proportional to (a–a⁻²), where a is the strain. This communication deals, however, with a kinetic analysis of melting of rat-tail tendons in concentrated aqueous urea at pH 7.0 and 37° C.