Pressure perturbation calorimetry

Kujawa and Winnik [209] reported recently that other volumetric properties of dilute PNIPAM solutions can be derived easily from pressure perturbation calorimetry (PPC), a technique that measures the heat absorbed or released by a solution owing to a sudden pressure change at constant temperature. This heat can be used to calculate the coefficient of thermal expansion of the solute and its temperature dependence. These data can be exploited to obtain the changes in the volume of the solvation layer around a polymer chain before and after a phase transition [210], as discussed in more detail in the case of PVCL in Sect. 3.2.2. 

Figure 13.12 Pressure perturbation calorimetry (PPC) experiment showing alternating pressure pulses of 5.1 and +5.1 atm as a function of time. The reaction mixture comprises 0.10 mM RNase A, 50 mM potassium acetate (pH 5.5) in the sample cell with identical buffer in the reference cell. The experiment is carried out at 10°C. (Permission to use the figure granted by MicroCal, LLC.)...

Lung-Nan, L., J.F. Brandts, MJ. Brandts, and V.V. Plotnikov. 2002. Determination of the volumetric properties of proteins and other solutes using pressure perturbation calorimetry. Anal Biochem 302 144—160. 

Abstract. Walter Kauzmann stated in a review of protein thermodynamics that volume and enthalpy changes are equally fundamental properties of the unfolding process, and no model can be considered acceptable unless it accounts for the entire thermodynamic behaviour (Nature 325 763-764, 1987). While the thermodynamic basis for pressure effects has been known for some time, the molecular mechanisms have remained rather mysterious. We, and others in the rather small field of pressure effects on protein structure and stability, have attempted since that time to clarify the molecular and physical basis for the changes in volume that accompany protein conformational transitions, and hence to explain pressure effects on proteins. The combination of many years of work on a model system, staphylococcal nuclease and its large numbers of site-specific mutants, and the rather new pressure perturbation calorimetry approach has provided for the first time a fundamental qualitative understanding of AV of unfolding, the quantitative basis of which remains the goal of current work. 

Fig. 9.5. Specific molar volumes of the folded (Vf) and unfolded (Vu) states of Snase as derived from densitometric measurements [15] (crosses, diamonds), pressure perturbation calorimetry [16] (open square), and spectroscopic high-pressure unfolding experiments [14] (filled squares). Dashed lines correspond to extrapolations...

Mention should be made here of the recently developed technique of pressure perturbation calorimetry (PPC), which measures the temperature-dependent volume change of a solute or colloidal particle in aqueous solution. PPC can also be used to detect thermotropic phase transitions in lipid model membranes and to characterize the accompanying volume changes and the kinetics of the phase transition. PPC essentially measures the heat change that results from small pressure changes at a constant temperature in a high-sensitivity isothermal calorimeter. For an excellent recent review on PPC as applied to lipid systems, the reader is referred to Heerklotz (19). 

Heerklotz PDH. Pressure perturbation calorimetry. In Methods in 39. Membrane Lipids. Dopico AM, ed. 2007. Humana Press, Totowa,... 

The thermal expansion of lysozyme in solution between 10 and 60°C was obtained from the partial molar volume. The intrinsic expansion of the protein was called anomalous since it did not behave like an ordinary solid or like a typical liquid [64]. Pressure perturbation calorimetry (PPC) is a relatively new experimental approach that allows one to obtain the thermal expansion (a) from the heat released or absorbed (Q) after short positive or negative pressure pulses (ca 5 bar) on proteins solutions from the relation [68-70]... 

Dzwolak et al. [123j have followed the aggregation of insulin under similar solution conditions and found an increase in the heat capacity and a decrease in thermal expansion from pressure perturbation calorimetry. 

A. Cooper, C. M. Johnson, J. H. Lakey, M. Nollmann, Heat does not come in different colours entropy-enthalpy compensation, free energy windows, quantum confinement, pressure perturbation calorimetry, solvation and the multiple causes of heat capacity effects in biomolecular interactions, in Biophys. Chem., 2001,93, 215-230. 

Heerklotz H, Seelig J (2002) Application of pressure perturbation calorimetry to lipid... 

This basic instrumentation can be complemented in various ways. For instance, sudden pressure changes may be applied to the system, thus obtaining additional thermodynamic information from the so-called pressure perturbation calorimetry . In this method the heat consumed or released after a pressure jump is measured, and from this volume changes associated with phase transitions may be derived. Another interesting modification is... 

ATT Atlanasio, F., Rialdi, G., Swierzewski, R., and Zielenkiewicz, W., Pressure perturbation calorimetry of poly(ethylene glycol) solutions in water, J. Therm. Anal. Calorim., 83, 637, 2006. 

KUJ Kujawa, P. and Winnik, F. M., Volumetric studies of aqueous polymer solutions using pressure perturbation calorimetry a new look at the temperature-induced phase transition of poly(Y-isopropylacrylamide) in water and D2O, Macromolecules, 34, 4130, 2001. 

Laukkanen, A., Valtola, L., Winnik, F. M., Tenhu, H. (2004). Formation of colloidally stable phase separated poly(A-vinylcaprolactam) in water a study by dynamic light scattering, microcalorimetry, and pressure perturbation calorimetry. Macrortwlecules, 37,2268-2274. 

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