Invited
Biological materials: ferroelectricity governed by biological refolding

Peptide and protein molecules are the basic biological scaffolds. To carry out their biological functions, any peptide/protein biomolecule is folded into a highly ordered architecture defined by its secondary structure, a-helix or b-sheet. These two conformational folds possess inherent structural ordering and provide highly specific biological activity. Native a-helical structures are acquired by many biological tissues such as skin, bone, tendon, and more. Biological functions of the b-sheet structures are related to neurodegenerative amyloid diseases such as Alzheimer, Parkinson, type II diabetes, and more.

In this work [1] we show that these different biological conformations exhibit two unique and dissimilar sets of fold-sensitive physical properties. It was found that in the a-helical state the peptide/protein nanostructures lack a center of symmetry. They are self-assembled into 1D-elongated arrays of peptide electrical dipoles, acquire stable electrical spontaneous polarization, and exhibit pyroelectric, piezoelectric, nonlinear optical, and electrooptical ferroelectric phenomena.

Amyloid b-sheet structure is the thermodynamically stable “final product” of a long-time refolding process in living organisms of disease-associated amyloid proteins from normally soluble metastable a-helical conformation to insoluble stable b-sheet fibrils. [2] This thermally-activated biological refolding a-helix-to-b-sheets state induces a deep structural reconstruction to centrosymmetric ordering followed by the growth of amyloid-like nanofibrils. The b-sheets fibrils lose their ferroelectric properties and acquire new effects of visible and tunable fluorescence and lossless photonic transport.

A wide range of the found fold-sensitive physical properties opens the avenue for a novel field of bioinspired peptide materials with exceptional piezoelectric, nonlinear optical, and FL properties towards their promising nanotechnological applications1 such as 3D-printed peptide piezoelectric devices, peptide visible fluorescent nanodots, for implantable peptide lab-on-chips for health monitoring.

References.

1. G. Rosenman, B.Apter, Invited Review, Appl. Phys. Rev. 9, 021303 (2022).

2. T. P. J. Knowles, M. Vendruscolo, and C.M. Dobson, Physics Today 68, 3, 36 (2015).