Design and testing of a new microcalorimetric vessel for use with living cellular systems and in titration experiments.

A new microcalorimetric vessel primarily intended for use with living cellular systems and in titration experiments has been designed and tested. The vessel, which forms a modular system, fits into an ampoule measuring cylinder of the LKB 'BioActivity Monitor'. It can be used with different sample cups, volume 1-3 ml, and can be equipped with different types of stirrer and sample holders for cellular materials. Experiments can be performed with or without medium perfusing through the vessel. Small quantities of reagents can be added to the sample compartment during the measurements. Stepwise calorimetric titrations can be performed by an automatic procedure. Test experiments reported include results of measurements with human T-lymphoma cells in stirred suspension and melanoma cells adhered to a polystyrene film in a stirred perfusing medium. Results from titration experiments where N-acetyl-D-alanine was bound to ristocetin A are reported, delta G degree' = -16.5 +/- 0.2 kJ mol-1 and delta H degree' = -32.1 +/- 0.4 kJ mol-1.