Epitaxial Growth of Peptide Nanofilaments on Inorganic Surfaces: Effects of Interfacial Hydrophobicity/Hydrophilicity

Abstract

The self-assembly of peptides and proteins has recently attracted much attention because of its scientific importance and widespread applications in the fields of nanomaterials, [1][2][3][4][5] crystallography, [6][7][8] and pathology. [9][10][11][12][13] Particularly, onedimensional growth of peptides or proteins on inorganic substrates has been recognized as a potential approach to the fabrication of functional nanostructures. [14][15][16] In these cases the peptide (or protein) is precisely assembled with the assistance of inorganic templates. [7,8] This feature allows the arrangement of peptide molecules in a predesignated orientation on substrates by proper design of the peptide sequences.Previous studies showed that different substrates have significant effects on the formation of nanofilaments. [17][18][19][20] As it is generally accepted that the hydrophobic interaction between the side chains is a driving force in the formation of peptide nanofilaments, it is very important to explore the effects of the substrate hydrophobicity/hydrophilicity on the relevant template-assisted epitaxial growth, which has not been systematically studied so far.Herein, we compare the self-assembly behavior of the peptide GAV-9 on hydrophilic mica and hydrophobic HOPG (highly ordered pyrolytic graphite) surfaces by in situ atomic force microscopy (AFM) to investigate how interfacial hydrophobicity/hydrophilicity influences the epitaxial growth of peptide nanofilaments.GAV-9, NH 2 -VGGAVVAGV-CONH 2 (Figure 1 a), consists of hydrophobic amino acid residues and is a conserved consensus of three neurodegenerative-disease-related proteins: a-synuclein, amyloid b protein, and prion protein, which are capable of forming amyloid fibrils in vivo and in vitro. [20][21][22] Unlike a-synuclein, GAV-9 with a concentration of 1.6 mm or less cannot form amyloid fibrils even when its solution is incubated under fibrillization-accelerating conditions [21] for a long time ( % 6 days), as characterized by AFM and turbidity measurements (data not shown). Circular dichroism experiments show that GAV-9 in fresh solutions adopts a random-coil structure, but forms b-sheets when dried (Supporting Information).However, AFM studies indicate that GAV-9 forms uniform nanofilaments from random-coil monomeric solutions through template-assisted growth on surfaces, including tapelike objects [19] on HOPG and fibrillike aggregates [23] on mica (Figure 2). Both the tapes and fibrils grow epitaxially across the surface and show three preferred orientations at 1208 to each other. The Fourier transform confirms its threefold symmetry (inset of Figure 2 b and Figure 2 e). It was also found that orientations of the tapes and the fibrils are consistent with the underlying atomic lattice of the substrates (Figure 2 a and Figure 2 b, Supporting Information). These results indicate that the self-assembly of GAV-9 is a onedimensional epitaxial growth process, similar to those previously reported. [14][15][16][17] Solid-state ATR (attenuated total reflectance) IR spect...

A comparative study on the self‐assembly of an amyloid‐like peptide at water–solid interfaces and in bulk solutions

“…Previous studies showed that hydrophilic and hydrophobic substrates have quite different effects on the formation of peptide nanofilaments (Giacomelli and Norde, ; Kowalewski and Holtzman, ; Lashuel et al, ; Sherratt et al, ; Zhang et al, ). In this study we use mica and HOPG as model substrates to study the surface effects on the self‐assembly behaviors of the N‐terminal‐deacetylated DN1, termed Pep 11 (NH 2 –Gln–Gln–Arg–Phe–Gln–Trp–Gln–Phe–Glu–Gln–Gln–NH 2 ), and compared with its self‐assembly behaviors in bulk solutions.…”

Kinetic Signature of Fractal-like Filament Networks Formed by Orientational Linear Epitaxy

“…1). This process is observed in a broad range of systems, including collagens [5][6][7][8], various β-sheet forming peptides [9][10][11][12][13][14], and organic nanofibers [15][16][17][18][19][20]. Commonly used substrates include mica, graphite, and KCl, where assembly occurs either in solution (mainly biofilaments) or via vapor deposition (organic nanofibers).…”

“…In these template-directed [7,9,12] or epitaxylike [8,10,11,14] assemblies, the molecular subunits forming a filament are often much greater than the lattice unit cell [8]. In the case of physisorbed films, lattice-imposed ordering of such incommensurate structures is known as "orientational epitaxy" [18,21,30,31].…”

“…1 (color online). Four types of OLE networks that have been experimentally observed: (a) Triaxial [8][9][10][11][12][13][14][15]18,19,21,27], (b) biaxial [5,6], (c) rectangular [16,17,28], and (d) isotropic [22][23][24][25][26]. (a),(b) Triaxial and biaxial form on hexagonal lattices, notably on mica.…”

Self-assembly of a terbium(III) 1D coordination polymer on mica

“…This self-assembly of molecules into chains is likely to be triggered by the presence of water on the air-cleaved mica surface. Indeed, the strong hydrophilicity of such surfaces has been demonstrated previously [44] and allows the molecules to reproduce the H-bonded network observed in the crystal packing of [Tb(hfac) 3 ·2H 2 O] n . This provides a significant amount of molecular nanochains deposited on the mica surface and organized along the crystallographic axes of the mica substrate.…”