Multi Angle / Dynamic Light Scattering (MALS)

Detailed biophysical characterization of biomolecules in solution

 
Lucia Banci Lucia Banci email hidden
Isabelle Billas Isabelle Billas email hidden
Christine Ebel Christine Ebel email hidden
Anastassis Perrakis Anastassis Perrakis email hidden

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Multi Angle / Dynamic Light Scattering (MALS) Details

User Guide

In a classical experiment, the proteins present in solution are separated using size exclusion chromatography and the hydrodynamic radius versus elution time for the proteins is then determined. Even for molecules with rg below the angular variation detection limit of 10 nm, the simultaneous measurements in the integrated MALS-QELS system provide complete results for rh as well as molar mass. Although molecular weights can also be determined via mass spectrometry and analytical centrifugation, only light scattering and analytical centrifugation monitor the properties of macromolecules in solution and provide information about possible oligomeric states. The comparatively short time of a DLS measurement greatly facilitates carrying out the multiple studies that may be needed to determine the impact of protein concentration, ligands, and pH. The QELS detector may be used also in a batch mode with special 10 µL cuvettes.

The combined MALS-QELS system can be used to analyze:

  • molecular mass, size distributions and oligomerization state of proteins and macromolecules.
  • protein-protein interactions.
  • copolymers, sugars, micelles, glycoproteins and protein conjugates.

Typical sample injection volume is 50-100 µL with a protein concentration that is related to the mass of the protein itself. For a 50 kD protein, 0.5 mg/mL are required. Samples must be absolutely free of particles, aggregates and bubbles. Therefore, the sample must be filtered before injection with low protein binding filters of 0.02 µm. Different buffers can be used and several components are tolerated after system equilibration.

All of the components required for MALS-QELS analysis are available at the facility:

  • Instrumentation: multi-angle light scattering (MALS), quasi-elastic light scattering (QELS) detectors, and high-performance liquid chromatographer (HPLC)
  • softwarefor analysis
  • size exclusion columns
  • filters

Technical Specifications

The MALS-QELS combined system gives the ability to size very small particles (1 to 30 nm hydrodynamic radius) on-line after they have been separated by some kind of fractionation technique or to size particles anywhere from 1 to 500 nm hydrodynamic radius if making batch measurements. Conformation results can be obtained for molecules ranging from below 1000 to millions of Daltons.