Kinetic phase behavior of distearoylphosphatidylethanolamine dispersed in glycerol

Phase behavior of distearoylphosphatidylethanolamine dispersed in excess gl ycerol has been examined by differential scanning calorimetry. Transformati on from lamellar-gel to lamellar crystalline phase was found to take place at temperatures near 74.9 degreesC upon cooling and near 76.3 degreesC duri ng heating scans. The transition can also be observed under isothermal cond itions at temperature in this range. The kinetics of the transformation fro m lamellar-gel to lamellar-crystal phase was analyzed by the well-known Avr ami equation. The apparent Avrami exponents were found to be approximately 1.6. The effective dimensionality of the growth pattern can then be set as 1, after taking into account the contribution of nucleation at the examinat ion temperatures. The activation energy of the phase transition was estimat ed as approximately 255 kJ mol(-1). The data are discussed in terms of deve lopment of successful cryoprotective strategies using glycerol. (C) 2001 El sevier Science B.V. All rights reserved.