An Amylose Antiparallel Double Helix at Atomic Resolution

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Science  09 Oct 1987:
Vol. 238, Issue 4824, pp. 205-208
DOI: 10.1126/science.238.4824.205


In the crystal structure of the polyiodide complex (p-nitrophenyl-α-maltohexaose2) · Ba(I3)2 · 22H2O, the maltohexaose units form an antiparallel, left-handed double helix with O-2 ... O-3 and O-6 ... O-6 hydrogen bonding and a central cavity that encloses two triiodide units. This structure contrasts with the parallel, left-handed double helix with no central cavity proposed for the A-and B-starch helix and the left-handed single helix in V-amylose and may be relevant for the stabilization of glycogen Structure.