Birefringence measurement of rapid structural changes during collagen denaturation

Linear birefringence, an optical property that results from a material's st ructure and composition, can be used to study dynamic changes in tissue str ucture, Single, 200 ps-long pulses from a Ho:YAG laser emitting 2.1 pm radi ation were used to induce changes in the linear birefringence of rat tail t endon. Such changes were measured on a millisecond timescale, The measured rate coefficients describing the denaturation are not predicted by previous studies of collagen denaturation induced by slower, lower-temperature heat ing. Two types of laser-induced collagen denaturation can be differentiated : thermal denaturation, which appears rate-limited, and thermomechanical de naturation, which is observed at higher laser radiant exposures, Neither pr ocess is described by standard Arrhenius-type kinetic models.