title: Three easy pieces.
abstract: BACKGROUND
  Differential scanning calorimetry is a powerful method that provides a complete thermodynamic characterization of the stability of a protein as a function of temperature. There are, however, circumstances that preclude a complete analysis of DSC data. The most common ones are irreversible denaturation transitions or transitions that take place at temperatures that are beyond the temperature limit of the instrument. Even for a protein that undergoes reversible thermal denaturation, the extrapolation of the thermodynamic data to lower temperatures, usually 25°C, may become unreliable due to difficulties in the determination of ΔCp.
  
  
  METHODS
  The combination of differential scanning calorimetry and isothermal chemical denaturation allows reliable thermodynamic analysis of protein stability under less than ideal conditions.
  
  
  CONCLUSIONS
  This paper demonstrates how DSC can be used in combination with chemical denaturation to address three different scenarios: 1) estimation of an accurate ΔCp value for a reversible denaturation using as a test system the envelope HIV-1 glycoprotein gp120; 2) determination of the Gibbs energy of stability in the region in which thermal denaturation is irreversible using HEW lysozyme at different pH values; and, 3) determination of Gibbs energy of stability for a thermostable protein, thermolysin.
authors.affiliation: Department of Biology, Johns Hopkins University, Baltimore, MD 21218, United States.
authors.forename: Arne
authors.initials: A
authors.lastname: Schön
authors.affiliation: Department of Biology, Johns Hopkins University, Baltimore, MD 21218, United States. Electronic address: ef@jhu.edu.
authors.forename: Ernesto
authors.initials: E
authors.lastname: Freire
mesh_terms: D000818:Animals; D001407:Bacillus / Q000737:chemistry; D001426:Bacterial Proteins / Q000737:chemistry*; D002152:Calorimetry, Differential Scanning; D002645:Chickens; D015699:HIV Envelope Protein gp120 / Q000737:chemistry*; D015497:HIV-1 / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009113:Muramidase / Q000737:chemistry*; D011489:Protein Denaturation; D017510:Protein Folding; D013696:Temperature; D013816:Thermodynamics; D013820:Thermolysin / Q000737:chemistry*
chemical_list: D001426:Bacterial Proteins; D015699:HIV Envelope Protein gp120; C514793:gp120 protein, Human immunodeficiency virus 1; D009113:Muramidase; D013820:Thermolysin
keywords: Chemical denaturation; DSC; HEW lysozyme; HIV-1 gp120; ICD; Thermolysin