Controlled Self‐Assembly of Amphiphilic Oligopeptides into Shape‐Specific Nanoarchitectures

Takagi

2010

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In this study, we describe the first demonstration of well-ordered multilayer thin films of gold nanoparticles through a layer-bylayer (LbL) technique assisted by a polypeptide template. Anionic poly(L-glutamic acid) (PLGA)-modified gold nanoparticles were prepared as building units for LbL self-assembly. Two types of synthetic polymers, poly(L-lysine) (PLL) and poly(allylamine), were used as polycations that carry the same amino groups at the side chain, although the former is a polypeptide and the latter is a vinyl polymer. The deposition process and the resultant multilayer films were characterized by means of absorption, circular dichroism, Fourier transform infrared and atomic force microscopy measurements. Experimental results revealed that LbL multilayer properties, such as thickness, conformation of the peptide component, homogeneity and periodicity of nanoparticle layers, were significantly affected by the kind of polycations present. In particular, the combination of anionic PLGA-coated gold nanoparticles and cationic PLL induced b-sheet formation, which enabled the fabrication of a homogeneously well-packed gold nanoparticle multilayer without aggregation.

“…A quartz plate was sonicated in a mixture of concentrated H 2 SO 4 and 30% H 2 O 2 aqueous (7:3 in vol.) for 30 min; thereafter, the plate was washed with pure water and dried.…”

Section: Lbl Assemblymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Layer-by-layer fabrication of well-packed gold nanoparticle assemblies guided by a β-sheet peptide network

Takagi

2010

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“…Langmuir monolayers of b-sheet peptides were, for example, reported to function as templates and serve as nuclei for the formation of inorganic nanocrystallites at the air-water interface. 12 Recently, numerous research groups have demonstrated that amphiphilic peptides self-assemble into b-sheet nanofiber architectures, [13][14][15][16][17][18][19][20] the surface of which has potential as a novel nanotemplate. [21][22][23] Several groups [24][25][26][27] have separately used b-sheet peptide nanofibers as templates to organize diacetylenes or dienes and promote their topochemical polymerization.…”

Section: Introductionmentioning

confidence: 99%

β-Sheet peptide-assisted polymerization of diacetylene at the air–water interface and thermochromic property

Taguchi

2011

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A peptide-diacetylene hybrid (PDH), in which 5,7-dodecadiynedioic acid was conjugated to the amphiphilic penta-peptide Leu-Lys-Leu-Lys-Leu, which can form b-sheets on both ends of the diacetylene moiety, was prepared through solid-phase peptide synthesis using fluorenylmethoxycarbonyl chemistry. Spreading experiments and spectroscopic observations showed that the PDH formed a stable Langmuir monolayer, primarily in the parallel b-sheet conformation at the air-water interface. When the PDH monolayer was exposed to ultraviolet radiation and a single-layer Langmuir-Blodgett (LB) film of the treated monolayer was deposited on a CaF 2 plate, the polymerization proceeded successfully and provided highly p-conjugated, blue-colored polydiacetylenes with absorption maxima at 653 and 640 nm, respectively. The polymerized PDH LB film displayed almost completely reversible thermochromism between blue and red (less conjugated) states upon heating and cooling. Polymer Journal (2012) 44, 195-199; doi:10.1038/pj.2011.105; published online 9 November 2011Keywords: b-Sheet; diacetylene; peptide; surface monolayer; thermochromism; topochemical polymerization INTRODUCTION Polydiacetylenes are conjugated polymeric materials with unique optical properties. The efficient polymerization of diacetylene yielding highly conjugated backbones requires the positioning of atoms in a crystalline lattice, and there is little displacement before and after polymerization; such a reaction is known as a topochemical reaction. 1-3 When properly aligned, diacetylene groups undergo ultraviolet (UV)-induced photopolymerization to form an ene-yne alternating polymer backbone, resulting in organized structures. In aqueous environments, these materials often appear blue or red, with the blue color indicating greater order in the conjugated p-system. 4 As the conjugated p-system becomes less ordered, the observed color shifts from blue to red. This unique chromatic property has made polydiacetylenes applicable to colorimetric biosensors. [5][6][7][8][9][10][11] We describe herein the thermoreversible color change of polydiacetylene prepared through b-sheet peptide-templated polymerization at the air-water interface. b-Sheet peptides are promising candidates for such a template or scaffold because they are often present in natural fibers as a structural element. Langmuir monolayers of b-sheet peptides were, for example, reported to function as templates and serve as nuclei for the formation of inorganic nanocrystallites at the air-water interface. 12 Recently, numerous research groups have demonstrated that amphiphilic peptides self-assemble into b-sheet nanofiber architectures, 13-20 the surface of which has potential as a novel nanotemplate. [21][22][23] Several groups 24-27 have separately used b-sheet peptide nanofibers as templates to organize diacetylenes or dienes and promote their topochemical polymerization. In this study,

“…The preparation of LKL16 and its self-assembling properties in water have been described elsewhere. 7 The azo(COO À ) 2 was synthesized by reacting the 4,4 0 -azodianiline with succinic anhydride. Photoisomerization of the azo(COO À ) 2 was first of all investigated in the presence of LKL16 at pH 9.2.…”

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confidence: 99%

“…In particular, much attention has been focused on the biological -sheet motif because of their association with neurodegenerative diseases like Alzheimer's, and as a building unit in the design of supramolecular nanofibers. [2][3][4][5][6][7] Recently, we have reported that the triblock-type amphiphilic peptide,…”

mentioning

confidence: 99%

Regulation of Self-assembling Process of a Cationic β-Sheet Peptide by Photoisomerization of an Anionic Azobenzene Derivative

Ushirogochi

2006

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Advances in molecular self-assembly are essential to establish practical guidelines to fabricate novel nanostructured materials. Our focus has been on artificial peptides as building blocks for the design of functional materials. 1 The interest in peptides is based on their ability to hierarchically self-organize into well-defined three-dimensional architectures than those which can be generated from conventional synthetic block polymers. In particular, much attention has been focused on the biological -sheet motif because of their association with neurodegenerative diseases like Alzheimer's, and as a building unit in the design of supramolecular nanofibers.2-7 Recently, we have reported that the triblock-type amphiphilic peptide, L 4 K 8 L 4 (LKL16), is an excellent -sheet foldamer and can be hierarchically self-assembled into amyloid-like nanofibers upon partial neutralization of the Lys residues at around pH 9.6,7 However, it is still difficult to control the spontaneous aggregation processes of peptides. Creating novel and facile methodology to regulate the self-assembling processes by external signals, such as light, 8 is therefore valuable to facilitate a bottom-up nanotechnology.Here we report a photo-responsive molecular system, in which self-assembling process of the cationic peptide intosheet nanofibers is regulated by photoisomerism of the exogenous anionic azobenzene derivative. Azobenzene is well known to change the overall geometry from planar to non-planar and the polarity of azo-linkage by trans-cis photoisomerization. In previous studies concerning azobenzene-conjugated peptide molecular systems, such changes in physical properties of azobenzenes have been utilized as a photosensitive switch to regulate conformation, 9 high-order structure, 10 and hydrogen-bonding pattern 11 of peptides. To our knowledge, however, it is the first report that the process of nanofiber formation is controlled by using a polarity change of photochromic additive, which causes slight change of total hydrophobicity of the target peptide.An azobenzene derivative with two carboxylate anions, azo(COO À ) 2 , was employed as a control agent for self-assembly of the cationic LKL16. The preparation of LKL16 and its self-assembling properties in water have been described elsewhere. 7 The azo(COO À ) 2 was synthesized by reacting the 4,4 0 -azodianiline with succinic anhydride. Photoisomerization of the azo(COO À ) 2 was first of all investigated in the presence of LKL16 at pH 9.2. In this condition, the azo(COO À ) 2 couples with the peptide, which is supported by FT-IR study (described later). The azo(COO À ) 2 existed in trans-form with an absorption at 370 nm upon dark adaptation. In contrast, UV irradiation of trans-azo(COO À ) 2 at 365 nm (4W UV lamp) caused a rapid conversion to the cisisomer within 1 min, as evidenced by a ca. 60% reduction in the peak intensity at 370 nm and an increase in the absorbance at 270 and 500 nm. Such photoisomerism of the azo(COO À ) 2 affected the conformational properties of LKL16. Figure...