Dual absorbance/fluorescence spectrometer

Stopped-flow systems have now reached dead time specifications well below one millisecond. There is, therefore, a need for detectors able to measure the signal on a microsecond time scale and with the highest signal to noise possible in order to save precious samples. Fluorescence and absorbance changes have been the most popular detection modes in rapid kinetics because these techniques are usually easy to set-up and are also highly sensitive.

Modern spectrometers now use a single detector for absorbance and fluorescence measurements. The detection is made using a high-sensitivity photomultiplier tube (PMT) optimized for the full wavelength range of the spectrometer. The switch from absorbance to fluorescence is made in a few seconds. A second detector is available as an option for simultaneous absorbance/fluorescence measurements, or to extend the detection range to FRET fluorescence, dual fluorescence or T-format anisotropy.

Speed and sensitivity

The MOS-200 is a simple, fast and sensitive rapid kinetics spectrometer. With its minimum 10µs time resolution and nM sensitivity, it is the ideal instrument for stopped-flow studies. Multi-time base acquisition modes are available so complex reactions with different steps can be followed easily. A motorized monochromator version (MOS-200/M) also exists for excitation scanning and multi-wavelength experiments, and its double light source allows the user to switch from steady-state to rapid kinetics almost instantaneously.

Bio-Kine is user-friendly software that controls the stopped-flow, the detection device, follows the acquisition, and analyzes data.

Single mixing applications

Two levels of operation are provided for mixer control. The first level is designed for rapid and easy experiment design. The user sets the mixing ratio, the size of the cuvette and the volume of samples. Color coded windows display calculated values and alert the user to out of range conditions. The estimated dead time is automatically displayed, and a pre-trigger is also available to be sure the stationary state is reached accurately. This interface is ideal for routine mixing designs, occasional users, or students.

Specifications

• 200-820 nm, and 0 nm (white light)
• Single or Dual light source (XeHg or XeHg/Xe)
• Manual or motorised monochromator
• Fast and sensitive
• 10µs to 1000 s sampling rate