Sequential Mixing
The sequential (or double) mixing accessory is specifically designed
to study the reactivity of intermediate and transient species.
Asymmetric, double mixing experiments are also fully supported.
This accessory equips the sample handling unit with two drive rams
(and 4 syringes). The first drive mixes two reagents (A and B) into
an aging loop and, after a user defined aging period, a second drive
mixes the aged solution with a third reagent (C) in the stopped-flow
cell.
Why use sequential mixing?
The standard SX20 or SX20-LED is equipped with two drive syringes, such that two reagents may be rapidly mixed together immediately prior to reaching the instrument’s observation cell. This works well for experiments of the type
A + B → AB, where AB is a supramolecular or coordination complex or a ligand bound to a biomolecule
or
A + B → C, where C is a new product of the reaction.
What about experiments with multiple steps?
The sequential mixing configuration equips the instrument with four syringes and two drive rams. The first drive ram mixes two reagents into an aging loop, and following a user-defined period (within the range of 14 ms to 1000 s, reproducible to within 1 ms), a third reagent is mixed with the first two immediately prior to the solution reaching the observation cell. The fourth syringe is for a buffer rinse. Thus, reactions of the type
A + B → AB + C → D or A + B → C + D → E are now supported.
Sequential mixing is also required for quench-flow operation. The quench-flow accessory replaces the standard stopped-flow cell and includes a millisecond dead time mixer connected to a detachable flow line, enabling rapid mixing of reagents, incubation for a selected period, quenching of the reaction, and sample recovery.
Features:
- Compatibility with all signal detection modes
- Built-in drive ram transducers providing full information with each experiment including: drive profiles, calculated
age time, drive volume per syringe, and a measurement of the dead-time - Aging times are reproducible to within 1ms
- No hardware reconfiguration is required when switching between short and long aging times
- The required aging time is set up in the software in the range 15ms to 1000s