Stopped-Flow/Quench-Flow

Instruments on the move with your experiments

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Over 300 Bio-Logic rapid kinetics instruments have been installed worldwide. The reason for our success lies in the quality of our instruments.

We understand that investing in instrumentation is not a trivial matter. What arrives in your lab today is going to be part of your research program for years to come. Our instruments are designed to last and grow with your research program. We are dedicated to supporting our instruments, be it the initial or the most recent instrument to come from our factory. Our first instruments are still in use today !

Over the years our instruments have grown and changed, fueled by customer / manufacturer interaction.
The Bio-Logic development team is dedicated to listening to client feedback and seeing which direction research is moving. Our instruments evolve with client needs and in anticipation of them.

This tradition continues on today with our current line of rapid mixing instruments.

The Bio-Logic SFM

The Bio-Logic Stopped-Flow Modules (SFM) are a fusion of technology, design and innovative control. Each element of the fusion compliments the others making the Bio-Logic SFM most powerful and flexible rapid mixing instruments existing today.

All Bio-Logic SFM instruments are based on our innovative use of stepping-motors to drive the syringes.
With modern microprocessor techniques, stepping-motors offer control and power unmatched by any other fast driving system.

The high performance of each SFM and the high speed of the stepping-motors is achieved because of the quality of the power-supply.

Each Mixer Power-Supply (MPS) unit contains independent power-supplies for each syringe, each driven by their own microprocessor. The sequence of impulses sent to the stepping-motors is stored in the memory of each motor board. One main microprocessor board synchronizes all the power supplies, and communicates with the computer via a serial interface.

Stepping motors advantages
The use of stepping-motors and a high quality power supply, gives each SFM the following advantages.

• Completely Variable Mixing Ratios:
  Because the flow rate and volume delivered by each syringe is independent of the others, mixing ratios are not fixed by syringes sizes. Mixing ratios are defined by the user, on-line.
• Precise Flow Rate and Volume Control:
  The flow rate and volume delivered by each syringe is chosen by the user, not defined by the instrument.
• Reproducibility and Regularity:
  The reproducibility and regularity of the linear translation of the syringes and the absence of pressure artifact allow optical recording during liquid flow.
  This capability greatly facilitates the determination of the initial phase of the reaction being monitored during stopped-flow experiments and makes the equipment suitable for accurate, continuous flow experiments.
• No Overpressure Artifacts:
  Syringe movements are completely controlled by microprocessor and can be halted in a fraction of a millisecond. This abolishes the need for a stop syringe during stopped-flow experiments and eliminates the stop artifact present in most conventional stopped-flow systems.
• Mixing of viscous solutions:
  Syringe velocity is programmed and thus is independent of the solution viscosity. Very asymmetric mixing such as pure glycerol against water can therefore be achieved.

Mixer technology
The mixer is the heart of a stopped-flow instrument. Although being often referred as "T-mixer" a straight T-connection between 3 tubes is capable of mixing two solutions only in limited cases (aqueous solutions, symmetrical 1:1 mixing, limited range of flow rate). The mixer used in the Bio-Logic Stopped-Flow are all based on the "ball mixer" technology which is a proven design for creating turbulence in the most stringent conditions. Because of it the Bio-Logic Stopped-Flow can operate in a wide range of fluidic conditions such as : high dilution ratio (up to 1:100), high range of flow rate (from 1 to 20 mL/s), mixing of highly viscous solutions against water (viscosity up to 2000 centipoises or 2 pascal.second have been achieved).

Applications

The application of the Bio-Logic SFM family of instruments is large and evolving. We have made our instruments as versatile as possible so that they are not the limiting factor in your research.

Here is a sampling of how our instruments have been used:

• Protein Folding
• Conformational Changes
• Substrate Binding
• Enzyme Kinetics
• Substrate Transport in Vesicles

• UV/VIS Absorbance
• Light Scattering
• Fluorescence
• Circular Dichroism
• Fluorescence Anisotropy
• FTIR
• X-ray scattering
• Conductivity
• Mass Spectrometry

• Substrate Binding
• Enzyme Kinetics
• Protein Folding Kinetics
• Conformational Changes
• Second Messenger Studies

• Radioactive labeling
• Hydrogen/Deuterium Exchange followed by NMR or Mass Spectrometry

• Trapping of kinetic intermediates by ultra-fast freezing

• Solid-State NMR
• EPR
• X-ray scattering
• EXASF

If you have questions about your specific application and would like to know how it can be supported by a Bio-Logic rapid-kinetics instrument, contact us !. We would be happy to discuss your application with you.

Mechanical Design

Each SFM is designed to be a versatile rapid-mixing instrument. It is not confined to a single functionality, but adaptable and expandable to a variety of rapid-mixing experiments.

This is due to the "open" mechanical design of an SFM. The syringes and motors are housed in a body that accepts attachments created for different types of experiments. Every SFM can be configured for Stopped-Flow, Quench-Flow, Optical-Quench and many other experimental conditions.

Switching from one mode of operation to another is just a matter of replacing one attachment with another. This operation requires only a few minutes and no specialized tools.

Vertical mounting of the SFM syringes facilitates purging of bubbles which might interfere with experiments. Bubbles can be evacuated from the instrument with a few pushes of each drive syringe.
The syringes, valves, and observation chamber can be very uniformly thermoregulated through the use of a circulating temperature bath connected to the SFM. The coolant flows through two internal circuits: one around the injection and reservoir syringe ports and the other through the valve block and observation head. This thermoregulation prevents the occurrence of temperature artifacts on a very wide temperature range, and permits rapid-kinetics studies even at low temperatures.

Quality Construction

Every SFM is carefully constructed of high quality materials. The parts in contact with the sample and the buffers are all machined out of materials selected for their inert characteristics

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Instrument control

The MPS32 software operates under the latest version of Windows environment (Win95, Win98, WinME, WinNT, Win2000, WinXP)

The software is easily configured for any of our SFM instruments. Through the use of various menus and windows, the MPS32 software allows the user to: 

• know the volume of the solution in each syringe
• perform manual or automatic movement of the syringes
• create a driving sequence with complete control of the volume delivered and flow rate of the syringes
• save or recall driving sequences
• start or stop experiments
• program the synchronization pulse used to trigger the acquisition system
• load the spectrometer data acquisition software: Bio-Kine

Dead and ageing time estimations are updated anytime the driving sequence or configuration parameters are changed.
These estimations are only possible because the user has complete control over syringe flow rate and volume delivered.

Up to 20 phases can be included in a driving sequence, allowing experiments involving complicated steps and washings to be executed with ease.

Automation of experiments is possible through the MPS32 software.
The MPS32 software can be used in conjunction with the spectrometer Bio-Kine acquisition and analysis software to automate experiments and acquisitions. Multiple shot averages can be made with a single button push.

SFM-20

The SFM-20 has been designed to fulfill the requirements of users that need only a basic 2-syringe instrument and are not willing to compromise on priming volume and sample economy. Experiments using in total only a few hundreds of microliter of reactants are within the capability of the SFM-20.

Even though it is our “basic” mixing instrument, its performance is on par with our 3 and 4-syringe instruments.

High precision drive mechanics allows dilution ratios exceeding 1/100.

The standard optical head is associated to a large choice of flow cuvettes. Time course of the reaction is followed by optical methods, see the Spectrometer pages for description of our dedicated fast kinetics UV/Vis spectrometers.

SFM-20 detail. Click to enlarge

Animated SFM-20
click here (316 kb)

SFM-300/400

SFM-400 in SF mode. Click to enlarge

SFM-400 in QF mode. Click to enlarge

SFM-400 in titration mode. Click to enlarge

They are still the first and only multi-mixing instruments that can be used as both optical stopped-flow and quench-flow instruments.

High precision drive mechanics allows dilution ratios exceeding 1/100.

Stopped-Flow configuration is achieved by installing the optical head associated to a large choice of flow cuvettes. Time course of the reaction is followed by optical methods, see the Spectrometer pages for description of our dedicated fast kinetics UV/Vis spectrometers.

Quench-Flow mode is obtained by installing ageing loops between the mixers and the programmable Quench-Flow valve at the exit of the instrument.

 

Number of syringes	3 (SFM-300) or 4 (SFM-400)
Driving mechanism	One stepping motor per syringe
Number of mixers	2 (SFM-300) or 3 (SFM-400)
Ageing volume between two mixers	adjustable from 25 to 1000 µl
Minimal dead time	0.6 ms with FC-08 cuvette - 0.25 ms with the microcuvette
Minimum injection volume per syringe	10 – 30 µl depending on installed cuvette
Observation cuvette	from 0.8 to 10 mm light path (click here for details)
Flow-rate range per syringe	0.010 – 10 ml/s depending on installed syringe
Variable ratio range	Continuously programmable from 1/1 to  more than 1/100
Minimal ageing time in Quench-Flow mode	< 2 ms
Trigger	Programmable trigger for data acquisition and synchronization of accessories
Material	PEEK
Syringe volume	1.9 – 10 ml
Dimensions	200 x 197 x 522 cm
Weight	13 kg (SFM-300) or 14 kg (SFM-400)

SFM-400 in SF mode using an umbilical connection. Click to enlarge

SFM-300 and SFM-400 diagrams for Stopped-Flow and Quenched-Flow mode

Stopped-Flow optics

It is also a unique feature of the SFM instrument, that the observation head allows insertion of standard 1 cm x 1 cm cuvette for steady-state measurements and calibration of the optical system.

The optical ports used for detection can be equipped with lens or fiber optics to direct the transmitted or emitted light wherever it is needed.

In most standard configurations, the optical head is set directly on the top of the Stopped-Flow instrument. This ensures mechanical and optical stability and also the lowest volume between the drive syringes and the last mixers. However, for some applications it is necessary to have a physical separation between these two parts of the instrument. This is achieved by the Umbilical link.

Stopped-Flow observation cuvettes

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If our standard cuvettes do not satisfy your specific experimental requirements, we invite you to contact us about custom-made cuvettes.

FC (fluorescence cuvette)

FC type cuvettes have blackened edges to reduce light scattering in fluorescence configuration. The best dead time performance are obtained with the FC-08 cuvette while the FC-15 and FC-20 cuvettes are the best choices for CD experiments in the far UV where their large aperture facilitates low noise recording at these wavelengths.

TC (transmittance cuvette)

TC type cuvettes have been primarily designed for absorbance and transmittance experiments, however in the TC-xx/yyF models, both sides along the light path are transparent. These models of cuvettes can also be used for fluorescence experiments using dilute samples and excitation with a laser or any other low divergence light source. Cuvettes of the TC.xx/10 type have a 1x1 mm² cross section and cuvettes of the TC.xx/15 type have a 1.5x1.5 mm² cross section.

Observation cuvettes - geometry

Notes:
(1) All cuvettes are in Suprasil (transparent from 185 to 2500 nm)
(2) Volume from a last mixer to center of observation area. Dead time is proportional to this volume and to the inverse of the total flow rate. The driving software issues an estimated dead time that takes into account all these parameters
(3) Light path when the cuvette is turned by 90°

Quench-Flow mode

SFM-300/Q features a three-syringe Quench-Flow with one delay line, two mixers and a diverting valve for waste and collect. This allows mixing between two reagents (in syringe 1 & 2 respectively), followed by ageing in delay line and subsequent quenching by mixing the aged mixture with the solution contained in the third syringe.

SFM-400/Q features a four-syringe Quench-Flow with two delay lines, three mixers and a diverting valve for waste and collect. This instrument allows more sophisticated mixing sequences such as mixing of two reagents (in syringe 1 & 2), first ageing in the first delay line followed by mixing with a third reagent (in syringe 3) and a second ageing phase in the second delay line before final quenching with the contents of the fourth syringe.

Various values of ageing time in the delay lines are obtained by modifying either the solution flow rate and/or the delay line volume (continuous-flow mode) or alternatively by including pauses in the sequence timing (interrupted-flow mode). The Windows based software allows an efficient control of the operational modes and of the solution flow rates as well as of washing and collect periods.

Flash quenching with a photoreactive reagent is also a mode that can be easily implemented with the SFM. (for details click here). Many other configurations are possible, and you are invited to inquire about their feasibility.

The commercial reference SFM-x00/QS has all the components for the Stopped-Flow (apart from Spectrometer) and Quench-Flow applications. An SFM-x00/S or an SFM-x00/Q can easily be updated to an SFM-x00/QS.

Accessories

These include:

The cryo-stopped-flow assembly extends the range of operation of the Bio-Logic stopped-flow instruments to far sub-zero temperatures. It allows rapid kinetics experiments to be performed down to -90°C  - click here for more details.

New submillisecond cuvette and mixer: This microcuvette accessory is a specially designed observation head that allows observation of very fast kinetics. Its provides the record performance of 0.25 ms dead time in stopped-flow mode (for SFM-300 & SFM-400, 0.4 ms for SFM-20) - click here for more details.

High Density Mixer - Used for minimizing convection artifacts when mixing solutions of widely differing viscosities. Highly recommended for protein folding-type experiments.

Delay Lines - Delay lines can be inserted between mixers to adjust sample ageing times for all types of experiments.

Titrator and Peltier element controller: Because of its extreme precision of volume delivery, the Bio-Logic stopped-flow instruments feature the most accurate titrator of the market. By a simple software choice and an easy hardware installation, any SFM-300/400 or SFM-20 can be converted in a high precision two syringe titrator. The titrator device also comes in a version that includes a Peltier Cell temperature cycler. This Peltier/titrator system benefit from a full integration with Spectrometer control software (Bio-Kine32). As such it can easily be used in absorbance, fluorescence, fluorescence anisotropy and circular dichoism - click here for more details.

Mix & Freeze - click here

Umbilical Connection - click here

Optical Quench Accessories - click here

Adaptation for EPR experiment - contact us

Bio-Logic also specializes in building custom accessories and adapting our instruments to new experimental methods. Please do not hesitate to contact us if you need a special development.

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