Pulse rapid-mixing device

Figure 6. Schematic representation of a rapid-mixing device for pulse radiolysis. C cell CS calibrated syringes (2 mL) D drain EB electron beam FP firing piston GI gas inlet RS reservoir syringes 3wT 3-way tap.

Enzyme reaction intermediates can be characterized, in sub-second timescale, using the so-called pulsed flow method [35]. It employs a direct on-line interface between a rapid-mixing device and a ESI-MS system. It circumvents chemical quenching. By way of this strategy, it was possible to detect the intermediate of a reaction catalyzed by 5-enolpyruvoyl-shikimate-3-phosphate synthase [35]. The time-resolved ESI-MS method was also implemented in measurements of pre-steady-state kinetics of an enzymatic reaction involving Bacillus circulans xylanase [36]. The pre-steady-state kinetic parameters for the formation of the covalent intermediate in the mutant xylanase were determined. The MS results were in agreement with those obtained by stopped-flow ultraviolet-visible spectroscopy. In a later work, hydrolysis of p-nitrophenyl acetate by chymotrypsin was used as a model system [27]. The chymotrypsin-catalyzed hydrolysis follows the mechanism [27] ... 

Diaphragm, piston, and peristaltic pumps all deliver liquids in pulses. This uneven delivery can cause dosing problems when mixing is not sufflcient to ensure a rapid distribution of the chemical into the process water stream. Devices and systems are available to help smooth the delivery from these types of pumps. These devices are sometimes called pulsation dampeners (Figure 7-6). There are several designs. 

Specific rate constants for vibrational excitation of the HF product of reaction (3.3) are given in Figure 3.IB. This reaction tends to favor higher vibrational states than does reaction (3.1). The influence of reaction (3.3) is quite evident in pulsed HF(DF) lasers based on the chain reaction in this case laser action is observed from several vibrational levels accessible only to reaction (3.3). For cw devices, however, the influence of slow mixing and rapid deactivation rates prevent laser operation from the highest vibrational levels and most of the laser output comes from the 1 0 and 2 -> 1 vibrational bands of HF and the 1 0, 2 1, and 3 -> 2 bands of DF. Laser... 

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