- Characterization of a novel, stage-specific, invariant surface protein in Trypanosoma brucei containing an internal, serine-rich, repetitive motif. Nolan, D.P., Jackson, D.G., Windle, H.J., Pays, A., Geuskens, M., Michel, A., Voorheis, H.P., Pays, E. J. Biol. Chem. (1997)