659 nm laser beam

SEC-MALS measurements were performed on a miniDAWN TREOS multi-angle light scattering equipment with detectors at three angles (43.6°, 90° and 136.4°) and a 659 nm laser beam (Wyatt Technology, CA). A Wyatt QELS dynamic light scattering module for determination of hydrodynamic radius and an Optilab® rEX refractometer (Wyatt Technology)
were used in-line with a size exclusion chromatography analytical column (Superdex 75 HR10/300, GE Healthcare). BSA was used as a control. The protein solutions (~2 mg/mL) were eluted in a 50 mM Tris HCl, 500 mM NaCl buffer, pH 8.0 with a flow rate of 0.5 mL/min. The data were processed using ASTRA7 software (Wyatt Technology) with the following parameters:
refractive index of 1.331, 0.890 cP for the viscosity of the solvent and a refractive index increment of 0.1850 mL/g. Protein solutions were centrifuged for 10 minutes at 10,000xg at 4°C prior to use.

Size exclusion chromatography coupled with multi-angle light scattering (SEC-MALS) studies of GRASP55 were performed on a miniDAWN TREOS multi-angle light scattering equipment with detectors at three angles (43.6°, 90° and 136.4°) and a 659 nm laser beam (Wyatt Technology, CA). A Wyatt QELS dynamic light scattering module for determination of hydrodynamic radius and an Optilab T-rEX refractometer (Wyatt Technology) were used in-line with a size exclusion chromatography analytical column (Superdex 200 HR10/300, GE Healthcare) [35] . Prior to any measurement, the samples were centrifuged at 11,000×g for 10 min at 4 o C. GRASP55 was eluted through the Superdex 200 column using 50 mM Tris HCl, 300 mM NaCl buffer, pH 8.0 with a flow rate of 0.5 ml/min.
Data collection and SEC-MALS analyses were carried out with ASTRA 6.1 software (Wyatt Technology). The refractive index and viscosity of the solvent were defined as 1.331 and 0.890 cP, respectively. dn/dc (refractive index increment) value for all samples was defined as 0.1850 mL/g (a standard value for proteins) [35] .