Temperature Dependence of the EPR Signal in Tendon Collagen

THE hypothesis of a solid-state control system governing connective tissue growth 1 has led us to study the electron paramagnetic resonance spectra (EPR) of non-irradiated human bone and its components 2–5 . We now report further results involving chiefly human tendon collagen. The tendon was clinically normal peroneus longus, and was studied in the air-dried state. The EPR spectrum of tendon collagen is a single line at g = 2.007 ± 0.006 having a width between peaks of the derivative of 10 ± 1 G. The line saturates homogeneously with a weak maximum at about 10 dB, and shows no angular dependence. A resonance with the same parameters is found in dog tendon. The intensity of absorption from human tendon collagen corresponds to about 4–15 × 10 15 spins/g. Magnetic field scans from 10–11,000 G at room temperature and at 114° K revealed no other consistently present resonances. At 114° K, the resonance is saturated even at the lowest incident microwave power level.