Composition-Gradient, Multi-Angle Static Light Scattering (CG-MALS) is a powerful technique for characterizing a wide range of biomolecular interactions.


Label-free and immobilization-free, CG-MALS is a rigorous yet versatile first-principles technique that measures interactions directly by monitoring the changes in solution molar mass that arise from the formation or dissociation of complexes. Apply CG-MALS to characterize:

  • Self- and hetero-association
  • Binding affinity from pM to mM
  • Absolute molecular stoichiometry (not just mole ratios)
  • Multi-valent or cooperative interactions; simultaneous self- and hetero-association
  • Kinetics of binding, aggregation or dissociation over time scales of seconds to hours

CG-MALS also characterizes non-specific interactions between proteins at high concentrations and between proteins and excipients, which impact colloidal stability of formulated biotherapeutics. Contact Wyatt to learn how CG-MALS can address your specific biomolecular interaction analyses, such as:

  • Drug-target binding for monoclonal antibodies or bispecific fusion proteins
  • Monovalent or multi-valent receptors
  • Self-association under a variety of buffer conditions
  • Multi-protein assemblies in structural biology
  • Colloidal stability at protein concentrations of 100 mg/mL and beyond

Instrumentation for CG-MALS

Composition-Gradient System

Calypso, CG-MALS, biomolecular interactions

Calypso® - Composition-gradient preparative system + software for carrying out and analyzing CG-MALS interaction analyses. Requires a MALS detector.

MALS Detectors

 dawn, molar mass determination, molar mass measurement, molar mass analysis, molecular weight measurement, molar mass characterization

DAWN® - The most sensitive MALS detector available, anywhere. Incorporates detectors at 18 angles to determine molar masses from 200 Da to 1 GDa and radii from 10 – 500 nm.

  • Standard option: ambient temperature
  • Heated/cooled option: -15°C to +150°C
  • High-temperature option: ambient to +210°C

The DAWN offers special options to handle fluorescent samples: fluorescence-blocking filters and an infrared, 785 nm laser.

- Second only to the DAWN in sensitivity. Incorporates detectors at 3 angles to determine molar masses from 200 Da to 10 MDa and radii from 10 – 50 nm. Ambient only.

DynaPro® NanoStar® - With sample volumes as small as 1.25 µL and temperature control spanning -15°C to +150°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) which may be used with the CALYPSO software to perform CG-MALS experiments with very little sample. Samples must be prepared manually, without benefit of the Calypso's automation.

Dynamic Light Scattering Detector

The CALYPSO® software does not analyze DLS data, but can be set to trigger DLS data acquisition by Wyatt’s ASTRA® software.

WyattQELS - A dynamic light scattering (DLS) module which integrates into a DAWN or miniDAWN MALS detector to provide simultaneous DLS measurements in the same scattering volume.

DynaPro® NanoStar® - With sample volumes as small as 1.25 µL and temperature control spanning -15°C to +150°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) which may be used with the CALYPSO software to perform CG-MALS experiments with very little sample. The NanoStar does double duty as an online DLS detector by installing its optical collection fiber into a Wyatt MALS detector.

Refractive Index Detector

Optilab, CG-MALS, dawn-heleos-II, binding affinity determination, light scattering, protein interactions

Optilab® - A unique on-line differential refractometer for measuring concentration of any macromolecule, regardless of chromophores. The high-concentration Optilab accommodates protein concentration up to 180 mg/mL.


CALYPSO™ - The CALYPSO software orchestrates CG-MALS analysis of biomolecular interactions, controlling sample preparation and delivery, data acquisition and data analysis. Provides the most extensive suite of association models available to determine the affinity and absolute molecular stoichiometry of macromolecular interactions including protein-protein binding, binding of aptamers and peptides or proteins, etc., as well as first-order analysis of reaction kinetics.

"Phenomenal service from hard working technical support staff"
"Binding studies with the Calypso are easy to set up, take only a few hours, and are easy to interpret. The technical support from Wyatt is both deeply and broadly knowledgeable. There are few places that offer the scope and quality of training Wyatt provides. I use Calypso II to measure both the stoichiometry and association constants of protein-protein interactions. Most binding methods have readouts that do not have physical meaning, such as maximum amplitude or slope of binding curve. Another major common problem is that models that describe the data contain parameters that are non-identifiable. Most experiments on the Calypso are not subject to the same issues. The determination of mass by the light scattering is not subject to the same concerns as other binding assays. 1) The mass is calculated on a calibrated instrument where all other parameters that affect light-scattering can be measured. 2) The structure that the Calypso data report has a structure that is informative on both the stoichiometry and the Kd. No more slopes or maxima! Even compared to the "Gold standard" analytical ultracentrifugation, Calypso (or composition gradient multi-angle light scattering CG-MALS) is superior. We found that non-1:1 stoichiometries of protein complexes can be very difficult to analyze with AUC data, whether using equilibrium sedimentation or velocity sedimentation. Although we get consistent results for the sedimentation rate for particles, the calculation of mass from any AUC data can run into identifiability issues. In contrast, experiments with CG-MALS can be designed to directly explore which stoichiometries can form at specific molar ratios of each particle. Furthermore, less sample and far less time is required. I strongly recommend using Wyatt instruments for particle characterization. Competitors like Malvern have not caught up and they do not provide any instrument that does anything comparable to the Calypso II. Wyatt provides unmatched service beyond the purchase of the instrument. We have used Wyatt instruments for over a decade without any drop in their excellent support." D. Brent Halling, University of Texas at Austin

Interested in other techniques or combining other techniques with CG-MALS?

SEC-MALS: Standard in protein, biopolymer and synthetic polymer characterizations labs around the world, Wyatt MALS detectors are valued for reliable and robust measurements.

FFF-MALS: Coupling an FFF system to a set of Wyatt MALS and/or DLS detectors creates a powerful system for accurate and robust characterization of molar mass and size distributions for simple or complex samples.

DLS: Measure the translational diffusion coefficients Dt of nanoparticles and colloids in solution by quantifying dynamic fluctuations in scattered light. DLS is suitable for ensemble measurements ranging from Rh values of 0.2 nm up to 5,000 nm.

MP-PALS: Wyatt Technology's breakthrough Massively Parallel Phase Analysis Light Scattering (MP-PALS) extends robust ELS measurements to proteins and other biomolecules in native buffer solutions. MP-PALS does everything conventional zeta potential instruments can do and much more.

SEC-IV: SEC-IV may be the optimal means of characterizing materials not amenable to SEC-MALS analysis. By simply adding a DAWN, transform a basic SEC-IV setup into a powerful SEC-MALS-IV polymer characterization station, to analyze absolute determination of molar mass and size regardless of conformation, branched polymers, copolymers and measure Mark-Houwink coefficients ab initio.