title: Temperature-induced phase transitions in proteins and lipids. Volume and heat capacity effects.
abstract: The partial specific heat capacity and volume of globular proteins and dispersions of phosphatidylcholines in aqueous solutions have been determined over a broad temperature range using a precise scanning microcalorimeter and a vibrational densimeter. It is shown that the temperature-induced, gel-to-liquid crystalline phase transition in phosphatidylcholines proceeds without a noticeable change in heat capacity but with a significant increase in the specific volume, whereas heat denaturation in proteins takes place without a noticeable change in the volume but with a significant increase in heat capacity. This principal difference between temperature-induced conformational phase transitions in proteins and lipids demonstrates clearly that heat denaturation of proteins, in contrast to the gel-to-liquid crystalline phase transition in lipids, cannot be regarded as a process similar to melting. Consequently, the 'molten globule' does not appear to be a suitable model for a heat-denatured protein.
authors.affiliation: Central Institute of Molecular Biology, G.D.R. Academy of Sciences, Berlin-Buch.
authors.forename: P I
authors.initials: PI
authors.lastname: Bendzko
authors.forename: W A
authors.initials: WA
authors.lastname: Pfeil
authors.forename: P L
authors.initials: PL
authors.lastname: Privalov
authors.forename: E I
authors.initials: EI
authors.lastname: Tiktopulo
mesh_terms: D002152:Calorimetry, Differential Scanning; D008786:Metmyoglobin; D008968:Molecular Conformation; D009113:Muramidase; D010713:Phosphatidylcholines; D011487:Protein Conformation; D011506:Proteins; D012259:Ribonuclease, Pancreatic; D013816:Thermodynamics
chemical_list: D010713:Phosphatidylcholines; D011506:Proteins; D008786:Metmyoglobin; D012259:Ribonuclease, Pancreatic; D009113:Muramidase