Physics and engineering of peptide supramolecular nanostructures

Abstract

The emerging "bottom-up" nanotechnology reveals a new field of bioinspired nanomaterials composed of chemically synthesized biomolecules. They are formed from elementary constituents in supramolecular structures by the use of a developed nature self-assembly mechanism. The focus of this perspective paper is on intrinsic fundamental physical properties of bioinspired peptide nanostructures and their small building units linked by weak noncovalent bonds. The observed exceptional optical properties indicate a phenomenon of quantum confinement in these supramolecular structures, which originates from nanoscale size of their elementary building blocks. The dimensionality of the confinement gives insight into intrinsic packing of peptide supramolecular nanomaterials. QC regions, revealed in bioinspired nanostructures, were found by us in amyloid fibrils formed from insulin protein. We describe ferroelectric and related properties found at the nanoscale based on original crystalline asymmetry of the nanoscale building blocks, packing these structures. In this context, we reveal a classic solid state physics phenomenon such as reconstructive phase transition observed in bioorganic peptide nanotubes. This irreversible phase transformation leads to drastic reshaping of their quantum structure from quantum dots to quantum wells, which is followed by variation of their space group symmetry from asymmetric to symmetric. We show that the supramolecular origin of these bioinspired nanomaterials provides them a unique chance to be disassembled into elementary building block peptide nanodots of 1-2 nm size possessing unique electronic, optical and ferroelectric properties. These multifunctional nanounits could lead to a new future step in nanotechnology and nanoscale advanced devices in the fields of nanophotonics, nanobiomedicine, nanobiopiezotronics, etc.

Symmetry of Bioinspired Short Peptide Nanostructures and Their Basic Physical Properties

“…As mentioned earlier, the asymmetric nanoscale structure found in FF PNT and LL PNT in the native phase [15] allowed the observation of ferroelectric and related phenomena, described by tensors of the odd rank. [12,15,16] One basic optical effect, which is described by the 3 rd rank tensor, is second harmonic generation.…”

“…The asymmetric nanoscale structure found in FF PNT [15] allowed the observation of the FF PNT nonlinear optical second-order response. Recently, the SHG method was applied to FF PNT, using a femtosecond laser, at a wavelength of 800 nm, with high pulse power density.…”

“…[12,15,16] One basic optical effect, which is described by the 3 rd rank tensor, is second harmonic generation. The origin of SHG is electron-photon interaction, wherein due to the original nonlinearity of a material having a structure with no center of symmetry, the fundamental optical wave generates a nonlinear polarization, which oscillates with twice the fundamental frequency.…”

“…This means that after heating, the FF PNT lose their piezoelectric and SHG properties, and also change their conformational packing. [15] Abstract: Supramolecular bioinspired peptide nanostructures are considered as a new frontier in materials science and engineering. The nano-crystalline packing of various peptide nanostructures, and especially those lacking a center of symmetry at the nanoscale, give rise to exceptional physical properties.…”

“…[10][11][12][13][14][15][16] It was shown that heat treatment at T > 150 8C induces irreversible phase transition in FF and LL PNT, wherein all the physical properties and the structure at all levels (molecular, space symmetry, wettability, and morphology) change. [12,15,17] This phase transition also leads to a transition in the crystal symmetry of the FF PNT, from the non-centrosymmetric hexagonal C 6 point group to a centrosymmetric orthorhombic D 2h point group. This means that after heating, the FF PNT lose their piezoelectric and SHG properties, and also change their conformational packing.…”