A stopped-flow mixer device for a batch microcalorimeter application to NAD-NADase reaction

A new molded polypropylene, diamond-like carbon (DLC)-coated mixing cell has been developed for use in the batch microcalorimeter. Reagent volume can be varied from 25 μ1 to 100 μ1. A 10 microcalorie reaction heat can measure to 5%. Repeat reactions can be done as often as every 10 min for a fast reaction. Reactions can be started within 1 h or less after loading. A pre-equilibrator and a temperature-controlled syringe drive unit permit solutions to be stored at 4°C while being runt at any temperature from −20°C to 40°C. The kinetics and enthalpy of reaction of NAD-NADase have been measured. ΔH is about 21 kcal/mol endothermic.