An observation chamber for a high-pressure stopped-flow apparatus.

A new design of the observation window to observation chamber seal is described for the Berger rapid stopped-flow apparatus. This design permits reliable operation of the apparatus and retains the features of a square non-deviating observation path with flush windows. Incorporation of fiber optic light guides for the observation path has made the apparatus insensitive to vibration artifacts. A demonstration reaction of calcium binding to EGTA is presented; the reaction, which is 90% complete within 2 ms, illustrates the capability of this apparatus for examining fast reactions.

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 microliters to 100 microliters. A 10 microcalorie reaction heat can be measured 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 degrees C while being run at any temperature from -20 degrees C to 40 degrees C. The kinetics and enthalpy of reaction of NAD-NADase have been measured. delta H is about 21 kcal/mol endothermic.