Figure 6 Charge heterogeneity of antibodies in HP CHO cell exposed to temperature downshift in bioreactors. (Black) constant temperature culture. (Gray) temperature downshift culture. All bioreactor samples were processed for protein purification. The charge heterogeneity of the antibodies was determined by isoelectric focusing electrophoresis. acidic, acidic charge variant. main, main peak. basic, basic charge variant. Experimental values represent three biological replicates ± SD. Two-tailed Student’s t-test was conducted using GraphPad Prism 8.0 ((*) p < 0.05, (**) p < 0.01, (***) p < 0.001 and (****) p < 0.0001).