Conformations of synthetic mode peptides for Plasmodium falciparum cirumsporozoite protein in ME sub(2)SO by super(1)H NMR and distance geometry calculations

A series of terminally blocked peptides consisting of a tetrapeptide repeat, Boc-Asn-Ala-(Asn-Pro-Asn-Ala) sub(n identical with 0,1,2,5,17)-Asn-Pro-OBzl, has been synthesized and one and two dimensional super(1)H NMR studies in dimethyl sulfoxide (Me sub(2)SO)-d sub(6) as well as distance geometry calculations have been carried out. The repeating tetrapeptide units constitute the central area of the circumsporozoite coat protein of human malaria parasite Plasmodium falciparum. The two dimensional nuclear Overhauser effect (NOE) data observed in Me sub(2)SO and the information from the temperature dependence of the amide proton chemical shifts were used as constraints in distance geometry calculations. The result suggests that each -(Asn-Pro-Asn-Ala)- tetrapeptide forms a structural unit, a considerable population of which exists as unique turnlike structures.