Study of phase transition in tetragonal lysozyme crystals by AC-nanocalorimetry

Differential ac-nanocalorimetric studies of a structural phase transition in the vicinity of 306 K in tetragonal lysozyme crystals have been carried out. It was found that the anomalies in the temperature dependences of heat capacity of the crystals look like λ-type anomalies. On the other hand, a pronounced temperature hysteresis has been observed at temperature cycling. The variation of experimental conditions such as relative humidity, frequency of the AC heat flow applied to the crystal of the order of 10 Hz, and heating rate seem not to affect the temperature of the anomaly in Cp(T).