Variant specific surface antigens from Trypanosoma equiperdum: chemical and physical studies.

Nine variant specific surface antigens were purified from clones of Trypanosoma equiperdum and characterized by amino acid analysis, isoelectric focusing and circular dichroism. The molecules showed extensive differences in their isoelectric points, and by comparison with the corresponding amino acid compositions, this variation seemed to be due to different amide contents. Circular dichroism data allowed one to divide the molecules into 4 groups according to their respective percentages in alpha-helical and beta-sheet structure.