Coil-helix transition of polypeptide at water-lipid interface

Abstract

Abstract. We present the exact solution of a microscopic statistical mechanical model for the transformation of a long polypeptide between an unstructured coil conformation and an α-helix conformation. The polypeptide is assumed to be adsorbed to the interface between a polar and a non-polar environment such as realized by water and the lipid bilayer of a membrane. The interfacial coilhelix transformation is the first stage in the folding process of helical membrane proteins. Depending on the values of model parameters, the conformation changes as a crossover, a discontinuous transition, or a continuous transition with helicity in the role of order parameter. Our model is constructed as a system of statistically interacting quasiparticles that are activated from the helix pseudo-vacuum. The particles represent links between adjacent residues in coil conformation that form a self-avoiding random walk in two dimensions. Explicit results are presented for helicity, entropy, heat capacity, and the average numbers and sizes of both coil and helix segments. arXiv:1405.2886v2 [cond-mat.soft] 8 Jan 2015Coil-helix transition of polypeptide at water-lipid interface 2

Kinetics of pHLIP peptide insertion into and exit from a membrane

“…We believe that our kinetics study, together with recent kinetics experiments on liposomes of different thickness of bilayer (5), theoretical (29), and computational (4) work, frames an improved understanding of the mechanism of pHLIP peptide insertion and exit from a bilayer in response to pH jumps. Fig.…”

Peptides of pHLIP family for targeted intracellular and extracellular delivery of cargo molecules to tumors

“…In general, highly cooperative transitions are hard to measure in biological systems with noise, especially when examining relatively short peptides like the class of pHLIP peptides (28). Only if the biological system is approximated to be infinite can a phase transition occur (37). Moreover, transition parameters for different peptides can only be truly compared when both peptides have precisely the same starting and ending states; although this condition is met for the membrane-inserted state (state III) of the peptides, which appears very similar among pHLIP variants, the condition that the initial state (state II) of the peptides be identical is not met.…”

Molecular chains under tension: Thermal and mechanical activation of statistically interacting extension and contraction particles

“…The segments of modified conformation are best represented by a self-avoiding walk of controllable randomness in two dimensions as described in Ref. [14]. The specifications for the multiplicity expression (2) are M = 2µ with µ = 1, 2, .…”

“…In the context of the coil-helix transition worked out in Ref. [14], we have named µ range parameter, t growth parameter, and τ nucleation parameter. The value of what is now the fourth parameter was kept fixed at ϑ = 1.…”

“…Further types will be introduced as needed in particular applications. We have already tested and used this methodology in a wide range of applications including collective modes with fractional statistics in magnetic chains [9], effects of condensation in D-dimensional quantum gases [10], lattice gases with short-range and long-range couplings [11], granular matter jammed by contact, gravity, or centrifuge [12,13], and polypeptides adsorbed to a water-lipid interface [14].…”