ISSN:
1089-7623
Quelle:
AIP Digital Archive
Thema:
Physik
,
Elektrotechnik, Elektronik, Nachrichtentechnik
Notizen:
A gas-solution reaction microcalorimeter has been developed for measuring the heat produced from a macromolecule in solution when the partial pressure of a reacting ligand is changed. The accumulated result of such stepwise heat processes enables the construction of a heat binding curve: namely the enthalpy per mole of reaction site versus the logarithm of the ligand activity [Gill, Richey, Bishop, and Wyman, Biophys. Chem. 21, 1 (1985)]. The high sensitivity (1 μcal) of the calorimeter is achieved by careful twinning and closed-loop proportional control achieved through continuous computer monitoring. A 15-μl liquid sample, for example 5-mM heme hemoglobin, is held in the form of a thin layer by means of a filter paper membrane. This configuration facilitates rapid equilibrium with exposed gases and allows for the completion of a given heat process within the range of 10 min. Gas partial pressures are accurately produced by means of a precision dilution valve incorporated into the calorimeter. The automatic determination of the heat binding curve is controlled by a small microcomputer programmed to change the gas partial pressure and to measure the heat that results from the change in the gas activity. An entire binding curve can be obtained on a sample of hemoglobin with as little as 20 nmol of oxygen binding sites.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1063/1.1139229
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