Rod‐Coil Globular Structures – Simple Models for Proteins

Abstract

Summary: In this article, we discuss the phase behavior of rod‐coil copolymers with two main methods. First, a scaling theory on different conformations is presented, which shows how micelles form. The circumstances of their stability is discussed. In the second part, we have formulated the general self‐consistent field theory (SCFT) for the rod(or helix)‐coil multiblock copolymer globule. This model and both approaches provide a simple description of the interplay between the secondary and tertiary structures in a globule α‐helix proteins.Pictorial representation of a used series ratio: each bar, zigzag line and fat dot correspond to $\hat G_{{\rm rod}} ,\;\hat G_{{\rm coil}} ,$ and σ1/2, respectively.magnified imagePictorial representation of a used series ratio: each bar, zigzag line and fat dot correspond to $\hat G_{{\rm rod}} ,\;\hat G_{{\rm coil}} ,$ and σ1/2, respectively.

Globular structures of a helix-coil copolymer: Self-consistent treatment

“…Fig. (18) shows that the crossover becomes sharper with increasing cooperativity (decreasing σ) as expected. For very high cooperativity (σ = 10 −5 ) and no selective interaction (χ ≈ 0), the fraction of stiff segments (Θ R = 0.2) is much smaller than 1/2.…”

“…In this section the derivation of the field theory is outlined. For a more detailed description see 18 . Regarding all three dimensional interactions and entropic contributions the helices are modelled as stiff rods.…”

Tunable assembly of amphiphilic rod–coil block copolymers in solution

“…52 Vilgis et al proposed the connected micelle formation of multiblock rod-coil copolymer in solution, where the stretching of the connecting coil chains costs additional entropy penalty. 53 Recently, Glotzer et al simulated three-dimensional assembly structures of rod-coil BCPs in concentrated solution by a combination of a coarse-grained, particle-based model and Brownian dynamics. 38,39 The volume fraction of the rods f has a profound effect on the phase diagrams (Fig.…”

Entropically driven transition to a liquid-crystalline polymer globule

“…The interaction parameters v and w are global two-and three-body interaction constants between all segments, whilst χ controls the strength of a selective two-body interaction (due to hydrophobicity) between the helical segments only. Further technical details can be found in [7]. At this point it is important to emphasize that all interactions in this model are point contact interactions.…”

“…To describe this local helix-coil transition a grand canonical formalism was used. A formal derivation of the grand canonical SCFT free energy functional F [ϕ(r), ψ(r, u); µ, ǫ, σ] is given in [7]. We introduced a field ϕ(r) associated with a flexible segment at position r and a field ψ(r, u) associated with a helical (rod-like) segment at position r with orientation u.…”