title: Role of lipids in the Neurospora crassa membrane. I. Influence of fatty acid composition on membrane lipid phase transitions.
abstract: The relationship between lipid composition and phase transition was investigated by differential scanning calorimetry for intact and membrane phospholipid extracts of wild-type (w/t) and the cel-(Tw 40) mutant of Neurospora crassa. The cel-(Tw 40) mutant (grown on minimal, sucrose medium supplemented with Tween 40 at approximately 34 degrees C) had approximately twice the saturated fatty acid content of w/t organisms grown at approximately 22 degrees C. The gel-liquid crystal phase transitions of ergosterol-free extracts derived from w/t and cel-(Tw 40) occur at -31 and -11 degrees C, respectively. The heats of transition (delta H) of these extracts were 1 and 13 cal/g, respectively. The addition of ergosterol (the predominant sterol in Neurospora) to the phospholipid extracts decreased the observed heats of transition, but did not alter the transition temperature. Intact Neurospora, whether w/t or cal-(Tw 40) did not manifest similar gel-liquid crystal phase transitions in the differential scanning calorimeter. However, an endothermic peak at approximately 30 degrees C was observed in intact cells and extracted phospholipids of both w/t and cel-(Tw 40) organisms. This peak was insensitive to the addition of ergosterol, had a low heat content (delta H congruent to 1 cal/g), and was reversible.
mesh_terms: D002152:Calorimetry, Differential Scanning; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D004875:Ergosterol; D005227:Fatty Acids / Q000032:analysis; D008563:Membrane Lipids / Q000032:analysis; D009154:Mutation; D009492:Neurospora crassa; D010743:Phospholipids / Q000032:analysis; D013329:Structure-Activity Relationship; D013696:Temperature
chemical_list: D005227:Fatty Acids; D008563:Membrane Lipids; D010743:Phospholipids; D004875:Ergosterol