Each of the monomers are composed of 9 antiparallel alpha helices. Two dimers associate in a staggered antiparallel manner to form a tetramer. The antiparallel strands form a helical shape. The diffraction pattern determined the helical nature of the double helix strands (antiparallel). DNA consists of two complementary antiparallel strands consisting varying patterns of nucleotides. Native SAA1 is a hexamer with each subunit assuming an antiparallel 4-helix bundle structure. The dimerization of myosin X is thought to be antiparallel. The Greek key motif consists of four adjacent antiparallel strands and their linking loops. SMPI is composed of two beta-sheets, each consisting of four antiparallel beta-strands. This protein was chosen because the beta barrel contains both parallel and antiparallel strands. Seven of these strands are parallel and the eighth runs antiparallel. The mechanism requires that the departing atoms or groups follow antiparallel trajectories. Beta-strands in many beta-barrels are arranged in an antiparallel fashion. If "J" is negative, the interaction favors electrons with antiparallel spins, potentially causing antiferromagnetism. The overall resistance is relatively low for parallel alignment and relatively high for antiparallel alignment.