SUMO-2 protein, SUMO-2 core domain, and the tail peptide corresponding to the first 14 residues were produced by chemical synthesis, and their secondary structures were analyzed by circular dichroism. The CD spectra of SUMO-2 and SUMO-2 core domain show distinct features and a-helical contents. In particular, the presence of the disordered tail in SUMO-2 lowers the alpha-helical content of the protein compared with SUMO-2 core domain and also explains the shift in the position of the minimum around 208 nm.