Organic solvents mediate self-assembly of GAV-9 peptide on mica surface

Self-assembly of peptides into fibrils and other morphologies has attracted much attention inmany fields,especially in nanofabrication,pathology and biochemistry.In this paper,self-assembly of GAV-9peptide in organic solvents,ethanol and acetone,was investigated using atomic force microscopy(AFM)and attenuated total reflectance-Fourier transform infrared spectroscopy(ATR-FTIR).The results indicatedthat GAV-9 self-assembled into various nanostructures in both solvents after deposited and evaporated onmica.Fibrils with β-sheet conformation were observed in both solvents when the peptide concentrationwas higher than 280 μM.However,ordered fibrils with β-sheet conformation were formed in ethanol,butnot in acetone,with a peptide concentration ranging from 7 μM to 28 μM.We attribute the formation ofvarious nanostructures to the different physicochemical properties of the polar organic solvents on the self-assembly of GAV-9 peptide.     

Synthesis and mass spectrometric characterization of a metal-affinity decapeptide: copper-induced conformational changes

A decapeptide with high affinity toward heavy metal ions (RCHQYHHNRE) has been prepared by Fmoc strategy using TGR resin as solid support. The model peptide provides a simple system that can be used for a systematic study of the impact of different metal ions on peptide secondary structure on a molecular level; histidine residues were incorporated into the peptide in a sequence similar to beta-amyloid peptide (Abeta1-40) to generate possible complexation sites for Cu (2+) ions. The peptide secondary structure, as investigated by circular dichroism, and self-assembled nanostructures were observed to depend strongly on the presence of copper and sodium dodecyl sulfate (SDS). Atomic force microscopy (AFM) revealed also that copper and SDS affected slightly the Abeta1-40 nanostructures. An explanation for the effect of metal ions and SDS on the self-assembly of peptides was proposed. The extensive beta-sheet formation may further promote peptide self-assembly into longer fibers.     

Fabrication of nanostructures through molecular self-assembly of small amphiphilic glyco-dehydropeptides

Self-assembled peptide-based nanostructures have been the focus of research in the past decade because of their potential applications in various biological systems. Normally, small self-assembled peptide nanostructures contain hydrophobic moieties, therefore, their solubility in aqueous systems poses the important challenge in the field of molecular self-assembly in order to make effective use of these in a wide variety of applications. To improve their aqueous solubility, the self-assembled amphiphilic α,β-dehydrophenylalanine containing small glyco-dehydropeptides, Boc-Phe-ΔPhe-εAhx-GA (I) and H-Phe-ΔPhe-εAhx-GA (II) with glucosamine (GA) attached at the C-terminal through a 6-aminocaproic acid linker, were synthesized, demonstrating the formation of nanostructures in aqueous media, which were characterized by DLS, AFM and TEM. Further, nanostructure II reduced auric chloride to gold nanoparticles and formed a peptide-gold conjugate (VII). The feasibility of using the nanostructures I and II as nanovectors for drug delivery was demonstrated by loading hydrophobic molecules, eosin and N-fluoresceinyl-2-aminoethanol (FAE) dyes. Besides, these peptides displayed antimicrobial activity against Micrococcus flavus, Bacillus subtilis and Pseudomonas aeruginosa. All these results advocate the potential of these nanostructures as efficient vectors for drug delivery applications.     

Self-assembly of a peptide sequence,EKKE, composed of exclusively charged amino acids: Role of charge in morphology and lead binding

The self-assembly of peptides is influenced by their amino acid sequence and other factors including pH, charge, temperature, and solvent. Herein, we explore whether a four-residue sequence, EKKE, consisting of exclusively charged amino acids shows the propensity to form self-assembled ordered nanostructures and whether the overall charge plays any role in morphological and functional properties. From a combination of experimental data provided by Thioflavin T fluorescence, Congo red absorbance, circular dichroism spectroscopy, dynamic light scattering, field emission-scanning electron microscopy, atomic force microscopy, and confocal microscopy, it is clear that the all-polar peptide and charged EKKE sequence shows a pH-dependent tendency to form amyloid-like structures, and the self-assembled entities under acidic, basic and neutral conditions exhibit morphological variation. Additionally, the ability of the self-assembled amyloid nanostructures to bind to the toxic metal, lead (Pb²⁺), was demonstrated from the analysis of the ultraviolet absorbance and X-ray photoelectron spectroscopy data. The modulation at the sequence level for the amyloid-forming EKKE scaffold can further extend its potential role not only in the remediation of other toxic metals but also towards biomedical applications.     

Designed aromatic homo-dipeptides: formation of ordered nanostructures and potential nanotechnological applications

Molecular self-assembly offers new routes for the fabrication of novel materials at the nano-scale. Peptide-based nanostructures represent nano-objects of particular interest, as they are biocompatible, can be easily synthesized in large amounts, can be decorated with functional elements and can be used in various biological and non-biological applications. We had previously revealed the formation of highly ordered tubular structures by the diphenylalanine peptide, the core recognition motif of Alzheimer's beta-amyloid polypeptide, due to specific aromatic interactions. We further confirmed this model and demonstrated that a non-charged peptide analogue, Ac-Phe-Phe-NH2, self-assembled into similar tubular structures. We later explored other amine and carboxyl modified diphenylalanine peptide analogues and revealed that these dipeptides can form ordered tubular structures at the nanometric scale. Moreover, a very similar peptide, the diphenylglycine, self-assembled into ordered nano-spherical assemblies. Here we extend our research and explore the self-assembly of other homo-aromatic dipeptides in which their phenyl side-chains are modified with halogen atoms (di-para-fluoro-Phe, di-pentafluoro-Phe, di-para-iodo-Phe), additional phenyl groups (di-4-phenyl-Phe), or with nitro substitutions (di-para-nitro-Phe). We also probed the effect of the alteration of the phenyl groups with naphtyl groups (di-D-1-Nal and di-D-2-Nal). In all cases, well-ordered nanostructures were obtained and studied by scanning electron microscopy, transmission electron microscopy and vibrational spectroscopy. Taken together, the current work and previous ones define the homo-aromatic dipeptide as a central motif for the formation of ordered self-assembled tubular, spherical and two-dimensional structures at the nano-scale.     

超分子多肽自组装在生物医学中的应用

近年来,自组装多肽纳米技术因其可形成规则有序的结构、具有多样的功能而备受关注。研究发现自组装多肽能在特定的条件下形成具有确定结构的聚集体,这种聚集体具备生物相容性好、稳定性高等优点,表现出不同于单体多肽分子的特性和优势,因此其在药物传递、组织工程、抗菌等领域具有良好的应用前景。文中介绍了自组装多肽形成的分子机理、类型、影响因素,综述了自组装多肽形成的纤维肽基水凝胶与自组装抗菌肽的最新进展,并提出目前多肽自组装技术所存在的问题及展望。     

自组装在多肽药物中的应用

自组装是指分子、纳米级结构材料等基本单元自发地组装成一个稳定而又紧密结构的过程。多肽可在各种非共价驱动力下自组装形成纳米纤维、纳米层状结构、胶束等不同的形貌。因多肽具有氨基酸序列明确、易于合成、便于设计等优势,多肽自组装技术成为了近年来的一个研究热点。有研究表明,对某些多肽类药物进行自组装设计或者使用自组装肽材料作为药物递送的载体,可以解决药物自身存在的半衰期短、水溶性差、生理屏障穿透率低等问题。本文重点介绍了自组装多肽的形成机制、自组装形貌、影响因素、自组装设计方法及其在生物医学领域的主要应用,为多肽的高效利用提供参考。     

Mechanisms of amyloid fibril self-assembly and inhibition. Model short peptides as a key research tool

The formation of amyloid fibrils is associated with various human medical disorders of unrelated origin. Recent research indicates that self-assembled amyloid fibrils are also involved in physiological processes in several micro-organisms. Yet, the molecular basis for the recognition and self-assembly processes mediating the formation of such structures from their soluble protein precursors is not fully understood. Short peptide models have provided novel insight into the mechanistic issues of amyloid formation, revealing that very short peptides (as short as a tetrapeptide) contain all the necessary molecular information for forming typical amyloid fibrils. A careful analysis of short peptides has not only facilitated the identification of molecular recognition modules that promote the interaction and self-assembly of fibrils but also revealed that aromatic interactions are important in many cases of amyloid formation. The realization of the role of aromatic moieties in fibril formation is currently being used to develop novel inhibitors that can serve as therapeutic agents to treat amyloid-associated disorders.     

Ile-phe dipeptide self-assembly: clues to amyloid formation

Peptidic self-assembled nanostructures are said to have a wide range of applications in nanotechnology, yet the mechanistic details of hierarchical self-assembly are still poorly understood. The Phe-Phe recognition motif of the Alzheimer's Aβ peptide is the smallest peptide able to assemble into higher-order structures. Here, we show that the Ile-Phe dipeptide analog is also able to self-associate in aqueous solution as a transparent, thermoreversible gel formed by a network of fibrillar nanostructures that exhibit strong birefringence upon Congo red binding. Besides, a second dipeptide Val-Phe, differing only in a methyl group from the former, is unable to self-assemble. The detailed analysis of the differential polymeric behavior of these closely related molecules provides insight into the forces triggering the first steps in self-assembly processes such as amyloid formation.     

Probing the role of aromatic residues in the self-assembly of Aβ(16–22) in fluorinated alcohols and their aqueous mixtures

The Aβ(16–22) sequence KLVFFAE spans the hydrophobic core of the Aβ peptide and plays an important role in its self-assembly. Apart from forming amyloid fibrils, Aβ(16–22) can self-associate into highly ordered nanotubes and ribbon-like structures depending on the composition of solvent used for dissolution. The Aβ(16–22) sequence which has FF at the 19th and 20th positions would be a good model to investigate peptide self-assembly in the context of aromatic interactions. In this study, self-assembly of Aβ(16–22) and its aromatic analogs obtained by replacement of F19, F20 or both by Y or W was examined after dissolution in fluorinated alcohols and their aqueous mixtures in solvent cluster forming conditions. The results indicate that the presence of aromatic residues Y and W and their position in the sequence plays an important role in self-assembly. We observe the formation of amyloid fibrils and other self-assembled structures such as spheres, rings and beads. Our results indicate that 20% HFIP is more favourable for amyloid fibril formation as compared to 20% TFE, when F is replaced with Y or W. The dissolution of peptides in DMSO followed by evaporation of solvent and dissolution in water appears to greatly influence peptide conformation, morphology and cross-β content of self-assembled structures. Our study shows that positioning of aromatic residues F, Y and W have an important role in directing self-assembly of the peptides.     

Self-Assembly of Phenylalanine Oligopeptides: Insights from Experiments and Simulations

Studies of peptide-based nanostructures provide general insights into biomolecular self-assembly and can lead material engineering toward technological applications. The diphenylalanine peptide (FF) self-assembles into discrete, hollow, well ordered nanotubes, and its derivatives form nanoassemblies of various morphologies. Here we demonstrate for the first time, to our knowledge, the formation of planar nanostructures with β-sheet content by the triphenylalanine peptide (FFF). We characterize these structures using various microscopy and spectroscopy techniques. We also obtain insights into the interactions and structural properties of the FF and FFF nanostructures by 0.4-μs, implicit-solvent, replica-exchange, molecular-dynamics simulations of aqueous FF and FFF solutions. In the simulations the peptides form aggregates, which often contain open or ring-like peptide networks, as well as elementary and network-containing structures with β-sheet characteristics. The networks are stabilized by polar and nonpolar interactions, and by the surrounding aggregate. In particular, the charged termini of neighbor peptides are involved in hydrogen-bonding interactions and their aromatic side chains form “T-shaped” contacts, as in three-dimensional FF crystals. These interactions may assist the FF and FFF self-assembly at the early stage, and may also stabilize the mature nanostructures. The FFF peptides have higher network propensities and increased aggregate stabilities with respect to FF, which can be interpreted energetically.     

一种溶酶体靶向的原位自组装短肽设计及抗肿瘤活性研究

肿瘤已成为威胁人类生命的一大杀手,目前主要采用手术和放、化疗等手段进行治疗,但由于放、化疗的细胞选择性差、毒副作用明显且易引起肿瘤细胞产生耐受(/药)性,不利于肿瘤的持续治疗,因此亟待研发具有定向定位优势、毒副作用低的新型靶向药物.原位自组装多肽能识别肿瘤部位的特异性高表达物质,在肿瘤部位靶向性聚集形成稳定的纳米结构,实现精准和高效治疗,有望成为一种新型的抗肿瘤药物.本研究基于多肽原位自组装的设计理念,利用溶酶体内组织蛋白酶L的催化活性,设计了靶向溶酶体且能够原位自组装的多肽分子Fmoc-FFRIKFERQ-OH,研究了该分子的自组装特性及抗肿瘤活性.结果显示,在体外酸性条件下,组织蛋白酶L能精准切割Fmoc-FFRIKFERQ-OH分子,其酶切产物FmocFFR-OH自组装形成长纳米纤维结构,对肿瘤细胞A375和SH-SY5Y均具有较好的杀伤作用.该分子通过靶向溶酶体杀伤肿瘤细胞且对正常细胞的毒性较低,有望成为一种新型的抗肿瘤药物.     

Short self-assembling peptides as building blocks for modern nanodevices

Short, self-assembling peptides form a variety of stable nanostructures used for the rational design of functional devices. Peptides serve as organic templates for conjugating biorecognition elements, and assembling ordered nanoparticle arrays and hybrid supramolecular structures. We are witnessing the emergence of a new phase of bionanotechnology, particularly towards electronic, photonic and plasmonic applications. Recent advances include self-assembly of photoluminescent semiconducting nanowires and peptide-conjugated systems for sensing, catalysis and energy storage. Concurrently, methods and tools have been developed to control and manipulate the self-assembled nanostructures. Furthermore, there is growing knowledge on nanostructure properties such as piezoelectricity, dipolar electric field and stability. This review focuses on the emerging role of short, linear self-assembling peptides as simple and versatile building blocks for nanodevices.     

Covalent capture: a natural complement to self-assembly

The utility of peptide self-assembly can be extended by covalent capture of these supramolecular materials. Disulfide bond formation, native chemical ligation, olefin metathesis, radical capture and oxidative lysine cross-linking have been used recently to help stabilize and characterize a variety of self-assembled peptides. These include natural peptides, proteins and protein mimics such as alpha-helical coiled coils, amyloid-like beta-sheet fibres, portions of p53, glutathione S-transferase and elastin as well as unnatural peptide constructs such as cyclic peptide nanotubes and cylindrical micelles of peptide amphiphiles.     

Self-assembly of the octapeptide lanreotide and lanreotide-based derivatives: the role of the aromatic residues.

We investigated the spectroscopic properties of the aromatic residues in a set of octapeptides with various self-assembly properties. These octapeptides are based on lanreotide, a cyclic peptide analogue of somatostatin-14 that spontaneously self-assembles into very long and monodisperse hollow nanotubes. A previous study on these lanreotide-based derivatives has shown that the disulfide bridge, the peptide hairpin conformation and the aromatic residues are involved in the self-assembly process and that modification of these properties either decreases the self-assembly propensity or modifies the molecular packing resulting in different self-assembled architectures. In this study we probed the local environment of the aromatic residues, naphthyl-alanine, tryptophan and tyrosine, by Raman and fluorescence spectroscopy, comparing nonassembled peptides at low concentrations with the self-assembled ones at high concentrations. As expected, the spectroscopic characteristics of the aromatic residues were found to be sensitive to the peptide-peptide interactions. Among the most remarkable features we could record a very unusual Raman spectrum for the tyrosine of lanreotide in relation to its propensity to form H-bonds within the assemblies. In Lanreotide nanotubes, and also in the supramolecular architectures formed by its derivatives, the tryptophan side chain is water-exposed. Finally, the low fluorescence polarization of the peptide aggregates suggests that fluorescence energy transfer occurs within the nanotubes.     

Effects of the sequence and size of non-polar residues on self-assembly of amphiphilic peptides

Peptides with alternating hydrophobic and polar amino acids have been shown to form stable beta-sheet secondary structures and self-assemble into hydrogel-like matrices in the presence of physiological salt concentrations. We hypothesized that the sequence and steric size differences of non-polar residues can affect the balance of peptide intermolecular forces in solution that drive self-assembly. To test this hypothesis, we designed a library of artificial amphiphilic peptides based on the sequence (FEFEFKFK)2 by substituting combinations of the non-polar residues glycine, alanine, valine, leucine and isoleucine for phenylalanine. Peptide structure and self-assembly were characterized using scanning electron microscopy, the Thioflavin T assay, transmission electron microscopy, X-ray fiber diffraction and circular dichroism spectroscopy. The sequence and steric size of non-polar residues are shown to cause variations in peptide secondary structures and create significant differences in the matrix morphology of self-assembled peptides.     

Simultaneous synthesis of temperature-tunable peptide and gold nanoparticle hybrid spheres

Hybrid spheres containing peptides and gold nanoparticles have been simultaneously synthesized in water using AG4 (NPSSLFRYLPSD) peptides that acted as a reducing agent to guide the nucleation and growth of gold nanoparticles and a precursor to form sphere-like structure by self-assembly where the size of hybrid spheres is precisely controlled by adjusting the operating temperature. The self-assembled peptide spheres remain stable even after selective removal of the gold nanoparticles by iodide etching. The amino acids containing the aromatic functional group in the peptide sequence significantly affect the construction of sphere structures. The surface of gold nanoparticles containing hybrid spheres has been functionalized using the thiol group linked to biomolecules. The ability to synthesize nanoparticle and self-assembled peptide structures with controlled size and composition in an environmental benign way will allow us to fabricate a new class of multifunctional organic-inorganic hybrid superstructures for various biomedical and electronic applications.     

肽基生物可激活的活体自组装纳米材料及生物医学应用

在生理环境下原位构筑自组装纳米材料,由于其生物体内的可控性、相容性及功能性优势,在临床应用方面具有广泛前景.利用病理条件在体内触发响应,能够在多重弱键相互作用下自发形成高级有序结构.其中内源性组装触发因素,如酶、pH、活性氧和配受体相互作用等,通过生物可激活的体内自组装(bioactivated in vivo ass...     

Molecular engineering of antimicrobial peptides: microbial targets,peptide motifs and translation opportunities

The global public health threat of antimicrobial resistance has led the scientific community to highly engage into research on alternative strategies to the traditional small molecule therapeutics. Here, we review one of the most popular alternatives amongst basic and applied research scientists, synthetic antimicrobial peptides. The ease of peptide chemical synthesis combined with emerging engineering principles and potent broad-spectrum activity, including against multidrug-resistant strains, has motivated intense scientific focus on these compounds for the past decade. This global effort has resulted in significant advances in our understanding of peptide antimicrobial activity at the molecular scale. Recent evidence of molecular targets other than the microbial lipid membrane, and efforts towards consensus antimicrobial peptide motifs, have supported the rise of molecular engineering approaches and design tools, including machine learning. Beyond molecular concepts, supramolecular chemistry has been lately added to the debate; and helped unravel the impact of peptide self-assembly on activity, including on biofilms and secondary targets, while providing new directions in pharmaceutical formulation through taking advantage of peptide self-assembled nanostructures. We argue that these basic research advances constitute a solid basis for promising industry translation of rationally designed synthetic peptide antimicrobials, not only as novel drugs against multidrug-resistant strains but also as components of emerging antimicrobial biomaterials. This perspective is supported by recent developments of innovative peptide-based and peptide-carrier nanobiomaterials that we also review.     

Self-assembly of amphipathic β-sheet peptides: insights and applications

Amphipathic peptides composed of alternating polar and nonpolar residues have a strong tendency to self-assemble into one-dimensional, amyloid-like fibril structures. Fibrils derived from peptides of general (XZXZ)(n) sequence in which X is hydrophobic and Z is hydrophilic adopt a putative β-sheet bilayer. The bilayer configuration allows burial of the hydrophobic X side chain groups in the core of the fibril and leaves the polar Z side chains exposed to solvent. This architectural arrangement provides fibrils that maintain high solubility in water and has facilitated the recent exploitation of self-assembled amphipathic peptide fibrils as functional biomaterials. This article is a critical review of the development and application of self-assembling amphipathic peptides with a focus on the fundamental insight these types of peptides provide into peptide self-assembly phenomena.