RX.2000 Rapid Kinetics Accessory for Stopped Flow
The RX.2000 Rapid Kinetics Accessory coupled to a FluoroMax® or FluoroLog® greatly enhances the accessibility of fast kinetic reactions. The capability of the fluorometer to sample individual data points every millisecond makes it an ideal tool for reactions initiated by rapid mixing with the RX.2000. This combination allows high quality measurement of rapid reactions which are completed in less than 100 ms.
Straightforward coupling of the RX.2000 accessory to a spectrofluorometer is achieved using the RX.2000 dual pathlength micro-volume cell fitted to the fluorometer's cell housing and a trigger accessory for externally initiating data acquisition from the stop syringe of the RX.2000.
The spectrofluorometer’s software has abundant features for acquiring and processing kinetic data including fitting facilities.
The experiment described below demonstrates the instruments sensitivity and ability to follow fast kinetics.
10 µM N-acetyltryptophanamide (NATA) was reacted under pseudo first-order conditions with 100-400 µM N-bromo-succinimide (NBS) to quench fluorescence[1]. The samples were excited at 281 nm, emission was ecorded at 358 nm. The 2 mm path of the dual pathlength cell was used.
Figure 1 shows overlaid excitation and emission spectra of NATA. Figures 2-4 show examples of fluorescence quenching with different concentrations of NBS. Whether driven pneumatically (with an optional accessory) or manually the short deadtime of the RX.2000 (6 ms) combined with the fast data acquisition of the FluoroMax® enables the reaction to be followed comfortably.
A total reagent volume of 160 ml was used per stopped-flow drive. Reaction rates in excess of 60 s-1 (Figure 4) were monitored for this reaction.
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The RX.2000 Rapid Kinetics Accessory in combination with the fast sampling FluoroMax® or FluoroLog® provides an efficient, straightforward and cost effective means of measuring fast kinetic reactions.
