Key benefits

The Mobius offers a unique suite of capabilities for mobility and size measurements of proteins, polymers and nanoparticles:

• Non-destructive analysis of fragile biomolecules
• Repeatable and accurate measurements in conductive buffers such as physiological saline
• Simultaneous measurements of size and mobility
• Automated sample handling or manual measurements
• Fluorescence blocking filter for sizing of fluorescing nanoparticles such as quantum dots

The Mobius characterizes the mobility of proteins and other biomolecules non-destructively and robustly, thanks to an innovative design enabling some unprecedented capabilities described more fully in the Advanced Technology tab.

Productivity, you say?

The Mobius features a novel, 170 µL flow cell providing advanced benefits, such as automated sample handling with a standard autosampler, to measure dozens of samples or conditions per day and maximize productivity. The high-pressure flow cell also affords connection to the Atlas^™ pressurization system for robust and reproducible analysis of biomolecular mobility, net charge and zeta potential in solvents with conductivity up to 100 mS/cm - about 6x physiological saline.

The combination of mobility + size results in a calculation of the nanoparticle's zeta potential or the protein's net charge. Thanks to simultaneous dynamic light scattering analysis of molecular/nanoparticle size alongside the mobility measurement, you can monitor changes to the sample in real time and adjust measurement parameters as necessary.

The closed, PEEK flow cell also means compatibility with a wide range of volatile organic solvents.

Massively parallel phase analysis light scattering

The Mobius characterizes the mobility of proteins and other biomolecules non-destructively, thanks to an innovative design that incorporates 32 parallel detectors denoted as 'massively parallel phase analysis light scattering', or MP-PALS.

MP-PALS is a true enabler for maximum sensitivity and short acquisition times. The combination of a powerful solid-state laser, precision optics and real parallel-plate electrodes near the optical path that do not distort electric field lines, permits application of low voltages with low current. Low voltage and current minimize perturbation of the sample, even in conductive solvents such as physiological saline, since exposure to high voltage may denature the sample and high currents produce heating and convection of the solvent, degrading the measurement.

Parallel, optimized optical channels

The combination of hydrodynamic radius and electrophoretic mobility are necessary to compute zeta potential, or net molecular charge. Most zeta potential detectors use a single avalanche photodiode for both size and mobility. This compromise means that dynamic light scattering (DLS) measurements, performed with light scattered into a high angle, may not be taken concurrently with mobility measurements that are performed with light scattered into a low angle.

The Mobius incorporates parallel optical channels that measure simultaneously - MP-PALS measurements of mobility at low angles utilize a completely separate detector than the DLS measurement of size via high angles. Both, of course, make use of the same high-quality laser beam originating in a single-longitudinal-mode solid-state laser.

Some samples are subject to degradation upon application of electric voltage and current, even at the very low values typically applied in the Mobius. Simultaneous monitoring of DLS and MP-PALS means that you can track changes to the sample, and modify measurement conditions accordingly to minimize degradation.

What about low-conductivity solvents?

Conversely, when high ionic strength is not an issue, you want to maximize mobility signals for the fastest and most accurate results. In addition to very low voltages, the Mobius can apply electric fields of hundreds of V/cm to extract robust signals in the presence of poorly conducting samples. The advanced technology incorporated into this instrument makes it the most versatile ELS detector available.

Autosampler operation

The Mobius flow cell enables automated sample handling with a standard autosampler. An Agilent autosampler and HPLC pump are controlled directly by DYNAMICS software to flush the system, inject sample, perform the measurement, and repeat with the next sample.

When measuring samples in high-ionic-strength buffers, an Atlas pressurization system should be incorporated in order to suppress bubbles formed by electrolysis in the cell, since these bubbles scatter light and corrupt the ELS signal. The Atlas is also controlled by DYNAMICS, making the entire sequence seamless.

Automating buffer conditions

Do you need to measure zeta potential or net molecular charge as a function of concentration, pH, ionic strength or excipient? The autosampler may even be programmed to automatically prepare samples at a series of buffer conditions. The Mobius measures conductivity directly in its flow cell, and pH by means of a Wyatt in-line pH detector. These data are recorded simultaneously with the size and mobility results.

Automation not for you?

If automation is not required, several convenient options are available for manual operation: samples may be injected directly into the flow cell (with or without the Atlas) or measured by means of cuvettes and dip electrodes.

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DYNAMICS^® - Software for electrophoretic and dynamic light scattering measurements in the Mobius. Calculates electrophoretic mobility, size and size distributions, and determines zeta potential, Debye-Hückel-Henry and effective charge.

DYNAMICS also controls Agilent autosamplers and pumps for hands-off analyses of dozens of samples per day.

DYNAMICS is offered with a 21 CFR Part 11 compliant Security Pack option, enabling the use of the Mobius in a GMP environment.

* Wyatt Atlas is required for conductivity above 8 mS/cm.

^† Solvent is Tris-Glycine buffer containing 25 mM Tris and 192 mM Glycine at pH 8.0. The standard deviation over ten thirty-second measurements is 10% of the mean value.

Host PC requirements may be found in Computer Requirements.

Specifications subject to change without notice.

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Other DLS & ELS instruments

DynaPro^® Plate Reader - The only commercially available instrument that measures DLS and SLS, for size and molar mass, directly in situ in standard 96, 384 or 1536 microwell plates. The non-perturbing DynaProPlate Reader offers integration with robot liquid handlers and multi-technique plate-based assay protocols. Temperature-controlled over 4 °C to 85 °C.

DynaPro^® NanoStar^® II - With sample volumes as small as 2 µL and temperature control spanning -10 °C to +120 °C, the NanoStar goes above and beyond traditional cuvette-based DLS instruments. It offers an optimized static light scattering detector in parallel to the DLS detection system in order to determine true molar mass and reliable particle concentrations.