WCX chromatograms of 1E10-ST (blue) and 1E10-AF (red). Gradient is represented in white (% A) and blue (% B), units are in the right axis. Inverted chromatograms were recorded after carboxypeptidase b treatment. Charged species are denoted with letters; prefix numbers indicate C-terminal lysine content for each peak. 1E10-ST gave rise to a continuous population of peaks due to the presence of terminal lysine while 1E10-AF showed almost no C-terminal lysine.