Step-scan differential calorimetry of protein denaturation: Modeling and experiment

• Published in: Thermochimica acta 2022-04, Vol.710, p.179181, Article 179181
• Main Authors: Mukhametzyanov, Timur A., Fatkhutdinova, Alisa A., Schick, Christoph
• Format: Article
• Language: English
• ISSN: 0040-6031; 1872-762X
• DOI: 10.1016/j.tca.2022.179181

•Step-scan calorimetry applied for reversible protein denaturation.•Theoretical step-scan curves are calculated and analyzed.•Quasi-equilibrium protein denaturation can be verified using step-scan technique.•Experimental step-scan curves of lysozyme in water and glycerol were obtained.•Negative slope of the protein excess heat capacity in water is discovered. Calorimetric step-scan curves of the reversible protein denaturation were modeled numerically. The quasi-equilibrium denaturation regime can be realized if the duration of isothermal steps is long enough so that the system is able to settle to equilibrium. We show the changes in the real and imaginary parts of the complex heat capacity during the denaturation process depending on the kinetic regime of denaturation. The practical application of the step-scan method for denaturation of lysozyme in water has revealed the negative temperature coefficient of the excess heat capacity of lysozyme. In the case of denaturation of lysozyme in glycerol studied by fast scanning calorimetry, the step-scan technique can be used to improve the quality of the baseline and reveal a heat capacity step after during denaturation. [Display omitted]