Reversible thermal transition of brain myelin proteolipid. A preliminary report on a high-sensitivity differential scanning calorimetry study

Abstract

Brain myelin proteolipid has been investigated using high-sensitivity differential scanning calorimetry (DSC) under various conditions. Crude proteolipid with a 40% (w/w) content of protein gave rise to a reversible transition, centered at about 60 degrees C. The specific enthalpy of the transition was 50 +/- 5 J X g-1 with a calorimetric to van't Hoff enthalpy ratio of 5.7 +/- 0.5. To our knowledge this is the first intrinsic membrane protein in which a reversible thermal transition has been detected and investigated by DSC. Similar experiments were carried out using the recombinants of delipidated proteolipid and the pool of natural membrane lipids; in this case the transition was less enthalpic and showed lower cooperativity. The recombinants with lecithins, however, did not show any transition at 60 degrees C.