Nano s dynamic light scattering system

The Nano-S Dynamic Light Scattering system (Malvern Instruments Ltd, Malvern, UK) equipped with a 633 nm laser and a fixed scattering angle (173°) was employed to analyze purity of MBP and MBP-netrin-4 delta protein as described previously [11 (link), 12 (link)]. Traditional DLS analysis provides the translational diffusion coefficient that was converted to Stokes radius or hydrodynamic radius via the Stokes−Einstein relationship using the DTS software (Malvern Instruments Ltd., Malvern, UK) supplied with the instrument. Both proteins were allowed to equilibrate for 4 min at 20°C prior to DLS measurements, after which multiple records of the DLS profile were collected for data analysis. Purity of MBP-netrin-4 delta (delta: missing the C-terminal NTR domain) was studied over the range of concentrations from 3.28 to 1.7 mg/ml whereas MBP alone was studied from 1.80 to 1.0 mg/ml in 1 x TBS buffer.

DLS data were collected on a Nano-S Dynamic Light Scattering system (Malvern Instruments Ltd., Malvern, UK) as previously reported [44 (link)]. Samples were filtered through a 0.1-μm filter (Millipore) and equilibrated for 5 minutes at 20°C before measurements. 15 measurements were made per sample, and for each condition three independent samples were tested.