EXAMPLE 6
Analytical Cation Exchange Analysis to characterize and determine proportion of charged isoforms was carried out on a MabPac SCX-10 3 μm, 4×50 mm, column (Thermofisher) at 0.5 ml min−1 with MES pH 5.6 buffer using salt gradient elution on an Ultimate 3000 HPLC (Dionex) with detection by UV at 280 nm.
Isoelectric Focusing was carried out using non-equilibrium pH gel electrophoresis using IEF 3-10 precast gels (Serva) run in a XCell Surelock Mini-Cell (Invitrogen) with BIO-RAD Power Pac HV and stained with SimplyBlue SafeStain (Invitrogen)
SDS PAGE was carried out on NuPAGE Novex Bis-Tris 4-12% gels (Invitrogen) run in a XCell Surelock™ Mini-Cell (Invitrogen) with BIO-RAD Power Pac HV, MOPs buffer, and stained with SimplyBlue™ SafeStain (Invitrogen). For analysis samples were diluted with loading buffer, NuPAGE LDS (Invitrogen) and for reducing SDS PAGE additionally reduced with DTT.
For Western Blots sample are first separated by non-reducing SDS PAGE, NuPAGE Novex Bis-Tris 4-12% gels (Invitrogen) run in a XCell Surelock Mini-Cell (Invitrogen) with BIO-RAD Power Pac HV, MOPs buffer, transferred to a PVDF membrane and detected using anti-human Kappa light chain AP; e.g. Sigma, Cat. No. K4377. Bound detection antibody is developed using a AP conjugate kit, Cat. No. 170-6432, Biorad.