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

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°C. The specific enthalpy of the transition was 50 + 5 J·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°C.