The antigenicity of sequential polypeptides. I. The synthesis of some sequential collagen models.

Preparations of poly-(glycyl-L-prolylglycine), poly-(glycyl-L-prolyl-L-proline), and poly-(β-alanyl-L-prolylglycine) via the corresponding tripeptide 4-nitrophenyl ester hydrobromides are described. A series of polypeptide antigens of structure H-(L-Ala-Gly-L-Pro)-OH with graded molecular weights were also prepared. The four low molecular weight members ( = 1, 2, 3 and 4) were obtained by stepwise classical condensation of tripeptide derivatives. Fractionation by gel filtration on Bio-Gel P-150 eluted with 50 per cent acetic acid was used to obtain five narrow fractions from a polydisperse preparation: these had single chain weight average molecular weights of approximately 2000, 3000, 6000, 11000 and 15000 respectively. The high molecular weight fractions possessed an ordered associated structure presumed to be a collagen-like triple helix, which was stable in 50 per cent acetic acid at room temperature.