A particular rigid left- or right-handed arrangement of a polymeric chain, characterised by the number of strands,the number (n) of units per turn and its pitch (p), the distance the helix rises along its axis per full turn. Examples of single-stranded helices are the protein helices: 
-helix:n = 3.6, p = 540 pm; 310-helix: n = 3.0, p = 600 pm; 
-helix: n = 4.4, p = 520 pm. See also double helix.
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