Investigating the permanent electric dipole moment of β‐lactoglobulin fibrils, using transient electric birefringence

Abstract

Amyloid fibrils, which are polymeric assemblies of protein molecules, have been intensively studied on a structural level, yet due to complications such as the disorder within the molecules, several aspects of their structure remain mysterious. Similarly, the kinetics of assembly are not well understood. Here we investigate the electric dipole moment of beta-lactoglobulin fibrils, a model amyloid fibril system, by applying the technique of transient electric birefringence. This moment appears to be large, and comparable to the total moment of the constituent protein monomers if they were joined in a chain, head-to-tail, without changing conformation, suggesting an ordered joining of monomers in the fibril. Such an ordered assembly may have implications for the assembly mechanism of beta-lactoglobulin fibrils in particular, and amyloid fibrils in general.

Amyloid Fibrils as Building Blocks for Natural and Artificial Functional Materials

“…They thus exhibit features associated with conventional charged polymers, with, however, a persistence length remarkably independent of the environmental conditions to which they are exposed; this observation can be rationalised in the light of the fact that the origin of the persistence length of amyloid fibrils is primarily the hydrogen‐bonding network at their core which is less affected by solution conditions than electrostatic repulsion responsible for the persistence length of conventional charged polymers. Furthermore, in contrast to other polymeric systems, they exhibit a combined chirality and polarity along their fibrillar main axis, a characteristic which allows for manipulations through electric fields of very weak intensities, or by adsorption at interfaces as symmetry breaking tool . Thus, a distinctive feature of amyloids at the mesoscale is their intrinsic rigidity, which together with their chiral, polar and charged nature, provides these systems with a rich physical behavior in one, two and three dimensions.…”

Adsorption at Liquid Interfaces Induces Amyloid Fibril Bending and Ring Formation

“…A polar twisted fibril has an anisotropy that distinguishes 'head' from 'tail' directions along the fibril axis; in F-actin this 'polarization' arises from the orientations required of G-actin monomers to effect self-assembly; 26 in an α-helix the N-C polymerisation breaks the polar symmetry and in cross-β amyloid fibrils such as those studied here the polarity is due to the molecular packing of β-sheets. [27][28][29] The polarity is reflected in variations in molecular structure along the exposed surface of the twisted ribbon. When this structure is placed in a heterogenous environment, as occurs near a solid surface or when immersed within a meniscus between two fluids (or fluid and gas), the inhomogeneity of the environment generally leads to unbalanced torques on the body (see Supplementary Note 2, Fig.…”

The initial stage of high-pressure induced β-lactoglobulin aggregation: the long-run simulation

“…In the case of the 1 + 1 scheme k rot = 1, because equal spherical particles rotate/orientate themselves with equal velocity. For the 1 + 2 scheme applies: with the rotational diffusion coefficients for monomer particles: where at η is the dynamic viscosity of the solvent, R 1 is the radius of the monomer particle and with l as length of the oligomer, d = 2 R 1 as diameter of the monomer particle and for dimers, trimers and higher chain‐like (‘rod‐like’) oligomers (Rogers et al. , 2006).…”

“…for dimers, trimers and higher chain-like ('rod-like') oligomers (Rogers et al, 2006). The interdependence (9) does not apply until l ⁄ d = 5 (Rogers et al, 2006).…”

“…for dimers, trimers and higher chain-like ('rod-like') oligomers (Rogers et al, 2006). The interdependence (9) does not apply until l ⁄ d = 5 (Rogers et al, 2006). In order to obtain D r for l ⁄ d = 2 we interpolate c in the interval 1 £ l ⁄ d £ 5 and substitute c by l ⁄ d = 2 into eqn (8) (Fig.…”