Advantages of MWA
MWA is more than replacing black and white television by color.
MWA is the most comprehensive and discriminative detector that Analytical Ultracentrifugation has ever seen.
The spectrometer collects 2048 wavelengths in a range of 700 nm with perfect reproducibility. In a classical absorbance detector, the monochromator is positioned mechanically, with a tolerance of +/- 2 nm. In contrast, the spectrometer is precise in a sub-nm-range and calibrated to yield the correct wavelength for each channel. Selecting 275 nm will yield 275 nm, eliminating the tolerance of a mechanical system.
Selecting more than one wavelength on a classical detector will cause the monochromator to be repositioned with every new scan. The tolerance of +/- 2 nm will apply for every new scan. For a scan series of one wavelength, this can mean that the extinction coefficient, governing the ratio of signal amplitude to concentration, will not be constant throughout the scan series. The MWA system will guarantee perfect reproducibility for any wavelength.
It was always risky to choose wavelengths on an absorption edge - the lack of reproducibility for wavelength positioning could cause intolerable deviations in signal intensity. However, the limitations of the Lambert-Beer-law restrict the applicable concentration range. When absorbance minima are too small and maxima too large, there is no other option than to dilute or concentrate the sample - or to take the risk of accepting the monochromator's error. As MWA does not exhibit this error, the scope of samples to be measured is increased considerably.
What is the use of monitoring the sedimentation of a protein with any other wavelength than 275 nm? AUC users would always choose the maximum of absorbance for detection, and why use any other wavelength with less absorbance, most likely producing noisier results? Because this data is redundant to a large extent, and in global fitting will produce less noise in the final result. Redundance is in fact two-dimensional: along the sedimentation axis, all wavelengths of the same species should exhibit the same distribution - along the wavelength axis, all sedimentation coefficients should exhibit the same spectrum.
MWA opens the way towards multiplex analysis of complex systems. Various components with different (or identical) spectral and sedimentation properties can be deconvoluted. No detection could be more specific. Only shortly after the first publications on MWA emerged, programmers have begun with the development of software capable of handling 3D-MWA-data. The power of multiplex analysis constitutes a new dimension of Analytical Ultracentrifugation.
Preserve runtime and sample
With MWA, the user does not need to know about the spectral properties of a sample beforehand. The typical approach of performing a wavelength scan first and then deciding on the best wavelength for detection is obsolete. Precious time in the beginning of an experiment is preserved, and the classical problem of needing to repeat the run with optimized conditions is avoided: all available data is collected; the decision on which data to use can be made afterwards.
Dynamic changes of absorbance properties
One merit of Analytical Ultracentrifugation, especially for quantum dots, has always been the combination of detecting sedimentation and spectral properties. However, shifts in absorbance during the course of sedimentation (due to aggregation, growth, transition...) need to be monitored over a larger range of wavelengths than the three a classical absorbance system can offer. MWA will monitor these processes with unmatched coverage and precision.
No other absorbance system to date exceeds Nanolytics Instruments' MWA detector. Scans are taken within seconds, calibration routines are equally fast. Sophisticated programming and controlling make this MWA faster than a classical system, even if the latter is set to acquire only one wavelength. Thus, Nanolytics Instruments' system is advantageous also if only one wavelength is needed: measuring sets of seven cells at low angular velocity, prohibitive on a classical system for rapidly sedimenting species, presents no problem.
In the classical design, the flash lamp is a vacuum seal. The rubber ring needed for leak tightness is seated on the bulb, emitting fumes when heated that deposit onto the lamp's surface. The loss of transmission is drastic, causing a need for frequent lamp cleaning. In MWA, the light source is located outside the vacuum compartment, and light is transmitted to the detector by fiber. The lamp requires no cleaning.
More information than I needed?
MWA does not boast to acquire three orders of magnitude more data without taking into account that most of this data is useless - many samples will absorb only in a small range of the spectrum.
Even for a small range of the spectrum, it is better to have a dozen datasets rather than one. All advantages given above will apply. The rest of the data can always be discarded, but they have required no additional time and effort in acquisition.