The elasticity of α-helices

Abstract

The elasticity of alpha-helices is examined using equilibrium molecular-dynamics simulations. From the statistics of curvatures and twists, we compute the elastic moduli of several representative alpha-helices, both in the presence and absence of aqueous solvent. We discover that the bending modulus (persistence length) of the helices is independent of the amino-acid sequence, although helices in water are slightly softer than in vacuum. The response of the helices under the action of an external force is also computed and compared with continuum mechanics predictions. Within the time scale of our simulation, we show that the properties of alpha-helices are well reproduced by an elastic and isotropic rod. The persistence length (bending modulus) of most alpha-helices in water or vacuum is approximately 100 nm, roughly twice that of DNA.

Ribosome exit tunnel can entropically stabilize α-helices

“…The persistence length obtained from the fit is l p ϭ 230 Ϯ 72. This value agrees well with a recent calculation of the elastic properties of long ␣-helices (27), which predicted l p Ϸ 263 (ϭ100 nm), although other authors quote a somewhat smaller number (28). Thus, entropic interactions are sufficient to account for the thermodynamic stabilization of the helical state under cylindrical confinement observed in our simulations.…”

Physics of Bacterial Morphogenesis

“…Large-scale allosteric movements are often transmitted by secondary structures. Without unfolding, ␣-helices can bend and twist and in the process can transmit significant forces (33,171,178). ␤-Sheets can also bend and store elastic energy (32,143).…”

“…It turns out that common deformations in proteins can be further analyzed by considering the mechanical properties of common secondary structures such as ␣-helices and ␤-sheets (21,32,33,143,171,178). Indeed, around 70% of all protein residues are in secondary structures; the rest are in random coils connecting these secondary structures.…”

Dynamic charge interactions create surprising rigidity in the ER/K α-helical protein motif

“…Previous computational analyses of alanine ␣-helices that ignore transient breaks in the ␣-helical backbone report a bending stiffness of Ϸ1 pN/nm (scaled for a 10-nm long ␣-helix) (18,19). However, in the presence of polar solvent, with partial water exclusion, the contribution of the ␣-helical backbone to the bending stiffness is unclear.…”