title: Quick-freeze differential scanning calorimetry and saturation transfer electron spin resonance: novel techniques for assessing phase transitions in biological membranes.
abstract: Quick-freeze differential scanning calorimetry (QF-DSC) and saturation transfer-electron spin resonance (ST-ESR) spectroscopy were used to study lipid gel-phase transitions in mature green tomato fruit microsomal membranes. ST-ESR of 12-doxyl methyl stearate labelled membranes proved to be reproducible and provided increased sensitivity to temperature-induced structural changes, allowing the detection of several transitions in isolated membranes (6 degrees C, 21 degrees C, 28 degrees C). QF-DSC led to the assessment of lipid gel phase transitions in isolated microsomal membranes and microsomal membrane lipids by enhancing the transition. A phase transition enthalpy of 114 J/g and an onset temperature of 29.8 degrees C were obtained for whole membranes while with isolated lipids values of 370 J/g and 19.9 degrees C were found.
authors.affiliation: University of Guelph, Department of Food Science, Ontario, Canada.
authors.forename: A G
authors.initials: AG
authors.lastname: Marangoni
authors.forename: D W
authors.initials: DW
authors.lastname: Stanley
mesh_terms: D002152:Calorimetry, Differential Scanning / Q000379:methods; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods; D005615:Freezing; D007425:Intracellular Membranes / Q000502:physiology*; D008861:Microsomes / Q000648:ultrastructure; D010944:Plants / Q000648:ultrastructure*; D013816:Thermodynamics