SANTA BARBARA, Calif., Sept. 8, 2011 — Wyatt Technology Corp. has released the Calypso, a composition-gradient multiangle light-scattering (CG-MALS) system that achieves accurate measurements of biomolecular interactions. It can determine both the affinity and binding stoichiometry for macromolecules in solution, with no need for sample tagging or immobilization that could influence the interaction. Antibody-antigen binding, hormone-receptor interactions and many other common biomolecular interactions occur at stoichiometries other than 1:1. Conventional separation techniques, such as size exclusion chromatography MALS and field flow fractionation MALS, have been used to study interactions, but they have limitations. As the molecules become separated in the course of dilution and fractionation, they no longer interact. And, upon reaching the detectors, the molecules often are not in equilibrium, nor in a well-defined kinetic state. Calypso complements traditional MALS separation techniques, keeping the molecules in proximity to probe their interactions. The analyzer was used in conjunction with an online ultraviolet/visible concentration detector and the proprietary Dawn Heleos MALS instrument to provide rapid and precise measurements of the interaction between an antithrombin antibody and human thrombin α. The equilibrium dissociation constant determined by the system agreed well with the manufacturer’s data as measured by ELISA. Both thrombin and the antibody exhibited no propensity for self-association, a finding that could not be evaluated by conventional ELISA. Calypso employs a series of unfractionated samples of various composition or concentration to characterize macromolecular interactions, including reversible self- and heteroassociation of proteins, reaction rates and affinities of irreversible aggregation, and virial coefficients. No special modifications are required. Instead, samples are unlabeled and entirely in solution. Calypso’s automation capabilities enhance productivity by improving repeatability and reliability, while minimizing time and effort.