Facile purification of mono-PEGylated interleukin-1 receptor antagonist and its characterization with multi-angle laser light scattering

Recombinant human interleukin-1 receptor antagonist (rhIL-1ra) was chemically conjugated with succinimidyl carbonate monomethoxyl polyethylene glycols of 5 kDa (SC-PEG5k) and 10 kDa (SC-PEG10k) molecular weight. A facile purification of the conjugates was achieved by one-step cationic exchange chromatography. The purity of mono-PEGylated protein was greater than 95%. The purified conjugate was characterized by multi-angle laser light scattering (MALLS) for determining the apparent gyration radius (rg) and hydrodynamic radius (rh). MALLS results showed that the conjugation of PEG markedly enhanced rg and rh of parent protein (rg: from 15.7 to 48.2 nm for the PEG5k and 81.9 nm for the PEG10k; rh: from 4.2 to 58.4 nm for the PEG5k and 102.3 nm for the PEG10k). The PEGylated rhIL-1ra retained 44.6% of binding activities to the cell receptor for PEG5k and 40.2% for PEG10k, compared to the original protein.