High Precision Microcalorimetry: Apparatus, Procedures, and Biochemical Applications

Abstract

Apparatus and procedures used for high-precision microcalorimetric measurements are described. The calorimeter is of the heat-conduction type and utilizes semi-conductor thermoelectric modules. The bicompartrnental reaction vessel is made of high-density polyethylene and holds about O.S mL of solution in each compartment. Imprecision of heat measurement is 0.2 percent when measuring 300 mJ of heat produced by a rapid chemical reaction. Three microcalorimeters are operated simultaneously using a microcomputer and a data acquisition system. Thermochemical and kinetic applications are described. The acquisition of data from an isoperibol solution calorimeter is also described.

A thermodynamic study of the hydrolysis of L-glutamine to (L-glutamate + ammonia) and of L-asparagine to (L -aspartate + ammonia)

“…They were calibrated electrically with a high stability d.c. power supply, calibrated digital voltmeter, standard resistor, and time-interval counter. Descriptions of the microcalorimeters and their performance characteristics, the data acquisition system, and the computer programs used to treat the results have been given by Steckler et al (9,10) The data acquisition system has recently undergone significant modernization. The voltages of the thermopiles of the microcalorimeters are now measured with HP model 34420A nanovolt meters.…”

A thermodynamic investigation of some reactions involving prephenic acid

“…They were calibrated electrically with a high stability d.c. power supply, calibrated digital voltmeter, standard resistor, and time-interval counter. Descriptions of the microcalorimeters and their performance characteristics, the data-acquisition system, and the computer programs used to treat the results have been given by Steckler et al (13,14) The data-acquisition system has recently undergone significant modernization. The voltages of the thermopiles of the microcalorimeters are now measured with Hewlett-Packard model 34420A Nanovolt Meters.…”

Thermodynamics of reactions catalysed by branched-chain-amino-acid transaminase

“…They were calibrated electrically with a high stability d.c. power supply, calibrated digital voltmeter, standard resistor, and time-interval counter. Descriptions of the microcalorimeters and their performance characteristics, the data-acquisition system, and the computer programs used to treat the results have been given by Steckler et al (11,12) At present, the voltages of the thermopiles of the microcalorimeters are measured with Hewlett-Packard 34420A Nanovolt Meters. These voltages are then recorded on a micro-computer and the areas of the thermograms are calculated by means of a numerical integration.…”