<i>Recent Progress in Microcalorimetry</i>

Calvet, E.; Prat, Henri; Skinner, H. A.; Hoffman, Joseph G.

doi:10.1063/1.3051541

Cited by 100 publications

(49 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…To determine the effect of any thermal lag on the DSC measurements, the DSC scans should be performed at different scan rates with a change in scan rate of at least an order of magnitude. Any dependence of the DSC thermodynamic quantities on scan rate due to the slow response time of the DSC can be corrected by the Tian equation which relates the observed power difference ∆P o (t) to the instantaneous power change, ∆P as follows [39],…”

Section: Correction For the Time Response Of The Dscmentioning

confidence: 99%

Measurement and analysis of results obtained on biological substances with differential scanning calorimetry (IUPAC Technical Report)

Hinz

Schwarz

2001

Pure and Applied Chemistry

View full text Add to dashboard Cite

Republication or reproduction of this report or its storage and/or dissemination by electronic means is permitted without the need for formal IUPAC permission on condition that an acknowledgmentAbstract: Differential scanning calorimeters (DSCs) have been widely used to determine the thermodynamics of phase transitions and conformational changes in biological systems including proteins, nucleic acid sequences, and lipid assemblies. DSCs monitor the temperature difference between two vessels, one containing the biological solution and the other containing a reference solution, as a function of temperature at a given scan rate. Recommendations for DSC measurement procedures, calibration procedures, and procedures for testing the performance of the DSC are described. Analysis of the measurements should include a correction for the time response of the instrument and conversion of the power vs. time curve to a heat capacity vs. temperature plot. Thermodynamic transition models should only be applied to the analysis of the heat capacity curves if the model-derived transition temperatures and enthalpies are independent of the DSC scan rate. Otherwise, kinetic models should be applied to the analysis of the data. Application of thermodynamic transition models involving two states, two states and dissociation, and three states to the heat capacity vs. temperature data are described. To check the operating performance with standard DSCs, samples of 1 to 10 mg mL -1 solutions of hen egg white lysozyme in 0.1 M HCl-glycine buffer at pH = 2.4 ± 0.1 were sent to six different DSC laboratories worldwide. The values obtained from proper measurements and application of a two-state transition model yielded an average unfolding transition temperature for lysozyme of 331.2 K with values ranging from 329.4 to 331.9 K, and an average transition enthalpy of 405 kJ mol -1 with values ranging from 377 to 439 kJ mol -1 . It is recommended that the reporting of DSC results be specific with regard to the composition of the solution, the operating conditions and calibrations of the DSC, determination of base lines that may be model-dependent, and the model used in the analysis of the data.

show abstract

Section: Correction For the Time Response Of The Dscmentioning

confidence: 99%

Measurement and analysis of results obtained on biological substances with differential scanning calorimetry (IUPAC Technical Report)

Hinz

Schwarz

2001

Pure and Applied Chemistry

View full text Add to dashboard Cite

show abstract

“…Because glass bead-water interaction is presumed to be negligible, (OQ/OP)/rn~ should be constant regardless of the proportion of glass beads, Therefore, ~ in equation (3) must have changed slightly as the proportion of glass beads increases. The peak height of a ballistic-type thermogram is affected somewhat by the heat capacity of the cell contents 1956, 1963 and the change in ~ is attrubuted to the loss in heat capacity accompanying the addition of glass beads to the cell. …”

Section: Resultsmentioning

confidence: 99%

“…Both theory and experiment (Calvet and Prat, 1956;1963) indicate that, for a thermogram of this kind,…”

Section: Methodsmentioning

confidence: 99%

Heats of Compression of Clay-Water Mixtures

Kay,

Low

1975

Clays and clay miner.

View full text Add to dashboard Cite

Abstract--Heats of compression of glass bead-water and clay-water mixtures were determined from the peak heights of the thermograms produced when these mixtures were subjected to pressure in a Calvet differential microcalorimeter. It is known that the heat of compression is directly proportional to the peak height. When the latter quantity was plotted against the pressure applied to any mixture, two intersecting straight lines were obtained. The change in slope at the point of intersection was interpreted as being the result of a pressure-induced higher-order phase transition in the water.The differential peak height, e, was defined as the rate of change of peak height with pressure/g of water present in the mixture. Hence, it is directly proportional to the rate of change of the heat of compression with pressure/g of water. Values of E were determined for both glass bead-water and clay-water mixtures containing different proportions of solids. It was found that E remained nearly constant with increasing proportions of glass beads, whereas, it varied in a non-uniform way with increasing proportions of clay, Also, its values in the clay-water mixtures were relatively high. Calculations showed that the difference in E values for the two mixtures could not be ascribed to the exchangeable cations associated with the clay particles. Consequently, it was ascribed to the effect of the particle surfaces on the structure of the vicinal water.The nature of water in clay-water systems has been discussed in several reviews (Low, 1961;Martin, 1962;Graham, 1964;Low and White, 1970). From these reviews it is evident that a controversy exists. The available evidence has been interpreted as being in favor of long-range order in the interlayer water, as being opposed to such order, or as being inconclusive. To help resolve the controversy, the authors conducted experiments on the heat of compression of water in aqueous systems of Na montmorillonite. Our hypothesis was that the structure of this water is different from that of bulk water. Therefore, it should respond differently to the application of pressure and yield a different heat of compression.Some of our results have already been published (Kay and Low, 1972). They show that the heat of compression of the water-montmorillonite system, its electrical resistance and the e.m.f, between reversible electrodes inserted in it, undergo an abrupt change at 20-30 psi. This abrupt change occurs only if the concentration of montmorillonite is above ~ 3.0% by vol and if a small amount of adsorbed hydrous aluminum oxide is present. It was interpreted as being the result of a pressure-induced, higher-order structural transition in the water.Additional tests of our hypothesis are reported in the present paper. In particular, it is our intention to show how the heat of compression of an aqueous Na-montmorillonite system changes with the concentration of Na-montmorillonite and with the * Journal paper no. 5531, Purdue University, Agricultural Experiment Station.t Present address: Department...

show abstract

“…We should like to note that such effect was reported by some authors studying plant tissues (15) and probably mixed microbial cultures (16). However, it was either not commented upon at all, or considered to be due to some kind of experimental error.…”

mentioning

confidence: 91%