The screening of the Pf genome [10] using generalized sequence profiles [11] identified several hundred proteins containing putative a-helical coiled coil motifs. Through proteome and transcriptome data [12] [13] [14] we assessed which of these molecules are expressed in the Pf parasite erythrocytic stage. The combined analysis/assessment identified over 100 segments associated with this stage and displaying the putative a-helical coiled coil motifs with high probability score (Table S1) . Out of these a-helical coiled coil fragments, in general 30-40 amino acids long, present either in the same protein or in different ones, 95 were chemically synthesized and HPLC purified. Among them, longer peptides (up to 70 amino acids), which contained one or more a-helical coiled coil domains, were also synthesized (antigenS 1, 12 and 83; Table  S1 ). The selected antigens were then tested in ELISA assays for reactivity with three panels of sera obtained from adult donors from Burkina Faso, Tanzania and Colombia, respectively. To our surprise, all of the a-helical coiled coil fragments were antigenic, though the prevalence of responders varied greatly (Tables 1 and  S1 ). In this manner, 71 proteins were identified whose lengths varied from 200 to 10,000 amino acids. Twenty-one peptides with the highest prevalence of responders and ELISA mean OD value were selected for further studies. Variation in recognition among the three panels of sera may be due to differences in the genetic background of the hosts, of the parasites and, most likely, to distinct malaria transmission conditions in the three regions. The high level of recognition of the a-helical coiled coil motifs may be explained by the fact that taken separately from the whole protein these fragments readily fold into the same stable structure in aqueous solution.