An improved method for obtaining thermal titration curves using micromolar quantities of protein

✍ Scribed by Norman V. Beaudette; Neal Langerman

• Publisher: Elsevier Science
• Year: 1978
• Tongue: English
• Weight: 680 KB
• Volume: 90
• Category: Article
• ISSN: 0003-2697
• DOI: 10.1016/0003-2697(78)90162-8

✦ Synopsis

Two simple modifications of a commercially available microcalorimeter allow rapid and accurate equilibration of sample with titrant and result in increased sensitivity. The modifications permit the rapid equilibration of the reaction vessel vapor space with solvent vapor and unambiguous determination of the temperature difference between the thermostat and the contents of the reaction vessel. A procedure is described for performing a thermal titration under conditions in which the system is undergoing a continuous thermal drift. The procedure is used to determine the standard enthalpy and free energy changes for the binding of ADP to bovine liver glutamate dehydrogenase. Only 0.3 pmol of protein sample was required. The observed values (AH"' = -13.0 5 0.7 kcal mol-', AC"' = -7.4 kcal mol-') agree within 5%, of the values determined by S.