Extracellular CHO HCPs were precipitated with methanol as described previously (Valente et al., 2014 (link)) and resolubilized in phosphate buffered saline. Concentrations of resolubilized HCPs were measured using a Bradford assay. Two sets of 30 μg CHO HCPs were reduced by sodium dodecyl sulfate (SDS) and DTT before being separated on 4-20% Mini-PROTEAN TGX precast gel (Biorad Laboratories, Hercules, CA, USA). Proteins were then transferred to a 0.45 μm polyvinylidene difluoride membrane (Life Technologies). Membranes were blocked in 3% non-fat dry milk in Tris-buffered saline with TWEEN 20 (TBST, Sigma-Aldrich Chemical Co.) for 1 hour and probed overnight at 4 °C with LPL N-terminus primary antibody (1:500 dilution in 3% milk block), which recognizes LPL residues 27-79 (Santa Cruz Biotechnology, Dallas, TX, USA). A second membrane was probed overnight at 4 °C with LPL C-terminus primary antibody (1:250 dilution in 3% milk block), which recognizes LPL residues 297-326 (Abcam, Cambridge, UK). The membranes were then probed with alkaline phosphatase-conjugated mouse anti-rabbit IgG (1:5,000 dilution, Sigma-Aldrich Chemical Co.) for 45 minutes, detected using enhanced chemifluorescence (ECF, GE Healthcare Life Sciences) substrate following the manufacturer's instructions and imaged using a Typhoon FLA-7000 scanner (GE Healthcare Life Sciences).