rotation per helix residue

symbol: $t$; unit: $\pu{rad}$
synonym: unit twist
https://doi.org/10.1351/goldbook.14215
Angle of rotation about the chain axis per helix residue.
Note: The value of \(t\) is obtained from the equation \[t = \frac{2\pi N}{M}\] where \(N\) is the number of helix turns in a chain identity period \(c\) and \(M\) is the number of helix residues in \(c\). In cases where the equivalence postulate does not apply, \(t\) is an average value.
Source:
PAC, 2011, 83, 1831. (Definitions of terms relating to crystalline polymers (IUPAC Recommendations 2011)) on page 1843 [Terms] [Paper]
Citation: 'rotation per helix residue' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.14215 RIS BibTex EndNote
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