Two-dimensional Self-assembly of a Designed Amphiphilic Peptide at Air/Water Interface

Abstract

A peptide having alternate sequence of hydrophobic and hydrophilic amino acid residues, (QAQL) 4 (CH 3 CO-(Gln-Ala-GlnLeu) 4 -NH 2 ), was designed to form a -sheet monolayer at the air/water interface. According to the designing of the peptide having charge free amino acid as hydrophilic residues, the peptide showed stable monolayer at wide range pH. The peptide monolayer prepared by Langmuir-Blodgett (LB) method showed an arranged nano-fibrous object. (QAQL) 4 -PEG was also an attractive building block for construction of nano-architecture by self-assembly at the air/water interface. PEG attached on the peptide segment showed a conformational transition from a flattened state to brush one, dependent on the compressing degree of the monolayer on water subphase. The conformational transition was simultaneously induced a morphological change of the nano-architecture from disk-like structure to fibrous array.KEY WORDS: Self-assembly / Air/water Interface / PEG-attached Peptide / -Sheet Fiber / Nano-architecture / The functional surface having a regulated morphology has a number of potential applications.1-5 The ordered structure is explored to create architecture in submicro/nano-meter scale, which could be applied for electro-devices, biointerfaces and super-hydrophilic/hydrophobic materials and so on. In order to construct a well-ordered structure on the material surface, two principal methods are suggested. One is ''top-down'' approach such as lithography and etching, which can construct a well-defined architecture at sub-micron scale.6,7 The other is ''bottom-up'' approach, which would be able to construct various nano-architectures, such as nano-fibers, nano-tubes and vesicles etc. 8,9 In these decades, molecular self-assembly has been a most promising technique to create such a fine-structure in nano-meter scale.Peptides and proteins are useful building block for construction of nano-structured materials, since the character of each amino acid and its sequence promote to a favorable secondary structure such as -helix, -sheet and flexible loop. These structural units show inter/intra-molecular interaction, and thus resulting in specific higher-ordered nano-organizations.10 Many researchers are making efforts to exploit the selfassembly of peptides and proteins. The formed nano-architectures such as micelle, gel and film, have versatile application in the field of drug-delivery, tissue-engineering and surface science.11,12 On the other hand, two-dimensional self-assembled structures are also attractive by virtue of the regulated structures such as stripe, lattice and honeycomb.13,14 These nano-architectures would be applied as a template for electro device and surface modification.We have focused on the construction of self-assembled structure of peptide at the air/water interface. The LB technique is an advanced method for preparing ordered organic monolayer, and it is expected to lead a designing of novel nano-device system. 15 When the peptide has an amphiphilic sequence, the phase direction of the peptide m...

Interfacial Self-Assembly of Antimicrobial Peptide GL13K into Non-Fibril Crystalline β-Sheets

“…Peptide self-association at the air/water interface has been employed for scaffold formation for templated biomineralization, − in food processing applications, and to design supramolecular assemblies and nanostructured surfaces. ,, Moreover, the air/water interface has been proposed as a model hydrophobic interface analogous to the membrane aqueous surface . Compression of peptide and protein monolayers has been used to probe the different stages of protein folding , and to mimic the macromolecular crowding conditions of different cell compartments .…”

A peptide-PEG conjugate-directed nanoperiodic hierarchical architecture by spatial selective self-assembly at the solid/water interface

“…In general, such features are remarkably exhibited by assembly at apolar/polar interfaces such as the air/water interface to give a variety of unique structures formed by different assembly behaviors. [15][16][17][18][19][20][21] The design of supplementary fragments having properties that are different in nature from the peptide segment affords lateral behavior and often enables unique self-assembly modes. 22,23 Peptide conjugates with alkyl chains at the peptide terminus reportedly form various types of tubular and fibrillar objects controlled at nanometer and sub-micrometer scales.…”