Pressure-Modulated Differential Scanning Calorimetry: Theoretical Background

Pressure-Modulated Differential Scanning Calorimetry: Theoretical Background
Received for review September 14, 2005. Accepted December 6, 2005.
Web Release Date: January 21, 2006
J?rg R?sgen*
Hans-J?rgen Hinz*
Anal. Chem.
ACS Publications
Copyright? 2006 American Chemical Society
Department of Biochemistry and Molecular Biology, 301 University Boulevard, University of Texas Medical Branch, Galveston, Texas 77555-1052
Institut f?r Physikalische Chemie, Westf?lische Wilhelms-Universit?t, Schlossplatz 4/7, 48149 M?nster, Germany
We demonstrate in this work and in the accompanying paper that it is possible to measure simultaneously heat capacity and expansibility of biomolecules in a single DSC experiment. In this study, we provide the theoretical basis for this new method based on rigorous statistical thermodynamics. The theoretical treatment presented here demonstrates that there are two additive contributions to the heat capacity at variable pressure, viz. (1) the isobaric heat capacity and (2) an expansibility term, and that these contributions can be experimentally separated to obtain simultaneously both heat capacity and expansibility in continuous DSC temperature scans preformed under pressure modulation. Equations that describe the mixed heat capacity and expansibility signal are derived, and experimental strategies as well as data extraction procedures are discussed.
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