An optical, real-time measurement of collagen denaturation

Linear birefringence is a property of collagenous tissue that results from both its composition and structure. Previous investigations have shown that birefringence provides an indication of structural changes in collagen during slow heating. We now report the birefringent response of both mature and young rat tail tendon (RTT) to laser-heating. The results indicate that denaturation of collagen from mature rats induced by a 200-mu s-long Ho:YAG laser pulse may not be described accurately by kinetic parameters. Several second-long pulses of CO2 laser radiation of collagen from young rats fit an Arrhenius model with E-a = 12.1 kcal/mol and A = e(18.03) s(-1). Typically, for slow-heating of collagen, E-a = 83 kcal/mol and A = e(120) s(-1).(1) Thus, it seems likely that the temperature and energy needed to initiate collagen denaturation is lower in young collagen, possibly due to its decreased hydroxyproline content and consequent decreased thermal stability.