Structural Transition in Peptide Nanotubes

Abstract

Phase transitions in organic and inorganic materials are well-studied classical phenomena, where a change in the crystal space group symmetry induces a wide variation of physical properties, permitted by the crystalline symmetry in each phase. Here we observe a conformational induced transition in bioinspired peptide nanotubes (PNTs). We found that the PNTs change their original molecular assembly from a linear peptide conformation to a cyclic one, followed by a change of the nanocrystalline structure from a noncentrosymmetric hexagonal space group to a centrosymmetric orthorhombic space group. The observed transition is irreversible and induces a profound variation in the PNTs properties, from the microscopic to the macroscopic level. In this context, we follow the unique changes in the molecular, morphological, piezoelectric, second harmonic generation, and wettability properties of the PNTs.

Symmetry of Bioinspired Short Peptide Nanostructures and Their Basic Physical Properties

“…[12] The disadvantage of these two microscopy methods is that they require special sample preparation. For example, for better contrast in SEM images, one usually needs to coat the peptide nanostructures with gold/ palladium.…”

“…[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.…”

“…[36] In the last few years, many investigations have been conducted on phase-transition phenomena in complex three-dimensional molecular and bioorganic systems. [36,37] Different types of phase transitions, such as reversible ahelix to random coil (also known as an "(un)folding process") in polypeptides and proteins, [37] and irreversible structural transitions [12] were described. The latter type of phase transition is very common in bioorganic systems, [38,39] and it results from variations at the molecular level that change the molecular crystals symmetry.…”

“…[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.…”

Bioorganic nanodots for non-volatile memory devices

“…1 In the last decade, several unique physical properties have been assigned to the FF tubular structure, and several possible applications have been purposed for them. A partial list includes: using the FF tubes as templates for metal nanowires or coaxial wires, 1, 3 as templates for the incorporation of photo-sensitizers, 4 as channels for nano-fluidic devices, 5 as efficient carbon electrode coating of supercapacitors, 6, 7 they exhibit one of the strongest measured piezoelectric signal among biological structures, 8 demonstrate pronounced non-linear optical response, 9 and possess unique photoluminescence properties. 10,11 Though the tubular structure of the FF tubes has an advantage for the described above applications, its main disadvantage is in its relatively large size, reaching the μm scale.…”