Purification of the recombinant copolymers by ammonium sulphate precipitation. The soluble acid-treated lysates of SELP-1020-A (A), SELP-520-A (B) and SELP-59-A (C) were saturated with increasing concentrations of ammonium sulphate (indicated above each gel). Depending on the concentration used, the copolymers either precipitated or stayed in the supernatant. (D) ( Increased purity was obtained by resuspending the precipitated copolymer (with 20% ammonium sulphate) in water and letting at 4°C with agitation followed by centrifugation or filtration (lane 1 – SELP-1020-A, lane 2 – SELP-520-A, lane 3 – SELP-59-A). The abnormal gel mobility of the recombinant protein was previously observed by other authors (Teng et al. 2009; Lyons et al. 2007; McPherson et al. 1992) and attributed to the hydrophobic nature of the proteins.