Coassembly Of Peptides Research Articles

Molecular recognition characteristics of co-assembled peptides on atomically flat graphite surfaces

Molecular recognition, involving the binding of two or more molecules, is widely found in multiple disciplines. It plays a crucial role in driving specific molecular functionalization or biological activities such as antigen–antibody interactions. Recently, the molecular recognition of single peptides self-assembly at interfaces has been widely investigated since their broad applications in biosensors and bioelectronics. However, the recognition characteristics of peptide-peptide co-assembly on solids has not been investigated yet, which provides a basis for potential multi-probes biosensing or structure-intermingled functionalized bioelectronic applications. Here, we explored the molecular recognition characteristics of co-assembled peptides on two-dimensional (2D) layered nanomaterials, specifically graphite. Our findings showed distinct surface characteristics of peptide co-assembly in comparison to the independent peptides self-assembly. Peptide co-assembly exhibited the nucleation and growth heterogeneities with reduced nucleation and growth rates, dominated by a diffusion-limited step as confirmed via carrying out the sequential-assembled experiments. Moreover, molecular dynamics simulation reveals a slowdown binding process of co-assembled peptides to graphite. Furthermore, the misattachment of one peptide to arrays of another types of peptide with distinct structural ordering orientations severely postponed peptide elongation. Therefore, our work provides valuable insight into the fundamental surface characteristics of two co-assembled peptides as they specifically recognize graphite surface via undergoing continuous surface behaviors from binding to diffusion until final ordering process. The formation of co-assembled peptide patterns on 2D layered nanomaterials incorporates multiple functions enabling to provide potential applications in intermingled peptide-based biosensing or bioelectronic nanodevices.

Bioinspired coassembly of peptide, imidazolecarboxaldehyde, and copper for nanozyme with laccase-like activity for colorimetric detection of epinephrine

Epinephrine plays a vital role in the central nervous system, but its abnormal levels will result in various diseases. Therefore, facile, rapid and accurate detection of epinephrine is essential for clinical application. Due to its phenolic structure, epinephrine can be detected through colorimetric assays as it is oxidized by laccase to form a colored quinone compound. In this work, a laccase-like nanozyme, diphenylalanine peptide/4-imidazolecarboxaldehyde-Cu (FF/ICA-Cu), was designed to mimic the active center of natural laccase. The as-synthesized FF/ICA-Cu nanozyme showed high laccase-like activity because of its structural similarity to the natural laccase active center. Moreover, it exhibited excellent stability and recyclability, even under harsh conditions. Based on its laccase-like activity, a sensitive and selective sensing strategy for epinephrine was developed. This approach offers a promising avenue for accurately detecting epinephrine and designing catalysts with potential for future industrial applications.

A Matter of Charge: Electrostatically Tuned Coassembly of Amphiphilic Peptides.

Coassembly of peptide biomaterials offers a compelling avenue to broaden the spectrum of hierarchically ordered supramolecular nanoscale structures that may be relevant for biomedical and biotechnological applications. In this work coassemblies of amphiphilic and oppositely charged, anionic and cationic, β-sheet peptides are studied, which may give rise to a diverse range of coassembled forms. Mixtures of the peptides show significantly lower critical coassembly concentration (CCC) values compared to those of the individual pure peptides. Intriguingly, the highest formation of coassembled fibrils is found to require excess of the cationic peptide whereas equimolar mixtures of the peptides exhibited the maximum folding into β-sheet structures. Mixtures of the peptides coassembled sequentially from solutions at concentrations surpassing each peptide's intrinsic critical assembly concentration (CAC), are also found to require a higher portion of the cationic peptide to stabilize hydrogels. This study illuminates a systematic investigation of oppositely charged β-sheet peptides over a range of concentrations, in solutions and in hydrogels. The results may be relevant to the fundamental understanding of such intricate charge-driven assembly systems and to the formulation of peptide-based nanostructures with diverse functionalities.

Formulate Adaptive Biphasic Scaffold via Sequential Protein-Instructed Peptide Co-Assembly.

To ensure compositional consistency while mitigating potential immunogenicity for stem cell therapy, synthetic scaffolds have emerged as compelling alternatives to native extracellular matrix (ECM). Substantial progress has been made in emulating specific natural traits featuring consistent chemical compositions and physical structures. However, recapitulating the dynamic responsiveness of the native ECM involving chemical transitions and physical remodeling during differentiation, remains a challenging endeavor. Here, the creation of adaptive scaffolds is demonstrated through sequential protein-instructed molecular assembly, utilizing stage-specific proteins, and incorporating in situ assembly technique. The procedure is commenced by introducing a dual-targeting peptide at the onset of stem cell differentiation. In response to highly expressed integrins and heparan sulfate proteoglycans (HSPGs) on human mesenchymal stem cell (hMSC), the peptides assembled in situ, creating customized extracellular scaffolds that adhered to hMSCs promoting osteoblast differentiation. As the expression of alkaline phosphatase (ALP) and collagen (COL-1) increased in osteoblasts, an additional peptide is introduced that interacts with ALP, initiating peptide assembly and facilitating calcium phosphate (CaP) deposition. The growth and entanglement of peptide assemblies with collagen fibers efficiently incorporated CaP into the network resulting in an adaptive biphasic scaffold that enhanced healing of bone injuries.

Coassembled Multicomponent Protein Nanoparticles Elicit Enhanced Antibacterial Activity.

The waning pipeline of the useful antibacterial arsenal has necessitated the urgent development of more effective antibacterial strategies with distinct mechanisms to rival the continuing emergence of resistant pathogens, particularly Gram-negative bacteria, due to their explicit drug-impermeable, two-membrane-sandwiched cell wall envelope. Herein, we have developed multicomponent coassembled nanoparticles with strong bactericidal activity and simultaneous bacterial cell envelope targeting using a peptide coassembly strategy. Compared to the single-component self-assembled nanoparticle counterparts or cocktail mixtures of these at a similar concentration, coassembled multicomponent nanoparticles showed higher bacterial killing efficiency against Acinetobacter baumannii, Pseudomonas aeruginosa, and Escherichia coli by several orders of magnitude (about 100-1,000,000-fold increase). Comprehensive confocal and electron microscopy suggest that the superior antibacterial activity of the coassembled nanoparticles proceeds via multiple complementary mechanisms of action, including membrane destabilization, disruption, and cell wall hydrolysis, actions that were not observed with the single nanoparticle counterparts. To understand the fundamental working mechanisms behind the improved performance of coassembled nanoparticles, we utilized a "dilution effect" system where the antibacterial components are intermolecularly mixed and coassembled with a non-antibacterial protein in the nanoparticles. We suggest that coassembled nanoparticles mediate enhanced bacterial killing activity by attributes such as optimized local concentration, high avidity, cooperativity, and synergy. The nanoparticles showed no cytotoxic or hemolytic activity against tested eukaryotic cells and erythrocytes. Collectively, these findings reveal potential strategies for disrupting the impermeable barrier that Gram-negative pathogens leverage to restrict antibacterial access and may serve as a platform technology for potential nano-antibacterial design to strengthen the declining antibiotic arsenal.

Programming co-assembled peptide nanofiber morphology via anionic amino acid type: Insights from molecular dynamics simulations.

Co-assembling peptides can be crafted into supramolecular biomaterials for use in biotechnological applications, such as cell culture scaffolds, drug delivery, biosensors, and tissue engineering. Peptide co-assembly refers to the spontaneous organization of two different peptides into a supramolecular architecture. Here we use molecular dynamics simulations to quantify the effect of anionic amino acid type on co-assembly dynamics and nanofiber structure in binary CATCH(+/-) peptide systems. CATCH peptide sequences follow a general pattern: CQCFCFCFCQC, where all C's are either a positively charged or a negatively charged amino acid. Specifically, we investigate the effect of substituting aspartic acid residues for the glutamic acid residues in the established CATCH(6E-) molecule, while keeping CATCH(6K+) unchanged. Our results show that structures consisting of CATCH(6K+) and CATCH(6D-) form flatter β-sheets, have stronger interactions between charged residues on opposing β-sheet faces, and have slower co-assembly kinetics than structures consisting of CATCH(6K+) and CATCH(6E-). Knowledge of the effect of sidechain type on assembly dynamics and fibrillar structure can help guide the development of advanced biomaterials and grant insight into sequence-to-structure relationships.

Anti-Glioma Activity Achieved by Dual Blood-Brain Barrier/Glioma Targeting Naive Chimeric Peptides-Based Co-Assembled Nanophototheranostics.

Peptide monomers can either self-assemble with themselves enacting a solo-component assembly or they can co-assemble by interacting with other suitable partners to mediate peptide co-assembly. Peptide co-assemblies represent an innovative class of naive, multifunctional, bio-inspired supramolecular constructs that result in the production of nanostructures with widespread functional, structural, and chemical multiplicity. Herein, the co-assembly of novel chimeric peptides (conjugates of T7 (HAIYPRH)/t-Lyp-1 (CGNKRTR) peptides and aurein 1.2 (GLFDIIKKIAESF)) has been explored as a means to produce glioma theranostics exhibiting combinatorial chemo-phototherapy. Briefly, we have reported here the design and solid phase synthesis of a naive generation of twin-functional peptide drugs incorporating the blood-brain barrier (BBB) and glioma dual-targeting functionalities along with anti-glioma activity (G-Anti G and B-Anti G). Additionally, we have addressed their multicomponent co-assembly and explored their potential application as glioma drug delivery vehicles. Our naive peptide drug-based nanoparticles (NPs) successfully demonstrated a heightened glioma-specific delivery and anti-glioma activity. Multicomponent indocyanine green (ICG)-loaded peptide co-assembled NPs (PINPs: with a hydrodynamic size of 348 nm and a zeta-potential of 5 mV) showed enhanced anti-glioma responses in several cellular assays involving C6 cells. These included a mass demolition with no wound closure (i.e., a 100% cell destruction) and around 63% collaborative chemo-phototoxicity (with both a photothermal and photodynamic effect) after near infrared (NIR) 808 laser irradiation. The dual targeting ability of peptide bioconjugates towards both the BBB and glioma cells, presents new opportunities for designing tailored and better peptide-based nanostructures or nanophototheranostics for glioma.

Modular co-assembly of peptides and polyoxometalates into underwater adhesives with photoluminescence and adjustable adhesion.

Supramolecular polymerization between cationic peptides and anionic polyoxometalates has emerged as a promising strategy for the creation of peptide-based biomimetic underwater adhesives. However, the extremely rigorous requirements for peptide design are an important obstacle to the fabrication of available peptide adhesives with controlled adhesion and versatile functionality. Inspired by marine sessile organisms in nature, here we reported a modular co-assembly method to easily produce peptide/polyoxometalate underwater adhesive materials through mixing two complementary cationic peptides (Pep1 and Pep2) with a single anionic polyoxometalate K6H[SiW9V3O40] in aqueous solution, which are not possible to be obtained from an individual peptide module. We demonstrated that the relatively hydrophobic Pep1 contributes to the bulk cohesion of the resulting adhesive, while the relatively hydrophilic Pep2 not only enables the interfacial adhesion but also regulates the bulk cohesion of the Pep1/Pep2/SiW9V3 adhesive. Rheological and shear adhesion tests showed that the macroscopic adhesion performance of the resulting adhesive materials could be conveniently adjusted by simply changing the molar ratio of the complementary peptide modules without any complicated peptide design. Interestingly, the luminescence properties of K11[Eu(PW11O39)2] (labelled as EuPW11) could be maintained within the Pep1/Pep2/EuPW11 adhesive even in a water environment. The lifetime of the Pep1/Pep2/EuPW11 adhesive was 2.19 ms. The fluorescence quantum yield of the Pep1/Pep2/EuPW11 adhesive was measured to be 27.46%. This study unveils that the modular co-assembly method can effectively simplify the material design of peptide/polyoxometalate underwater adhesives, which will significantly broaden the horizon of material pools and extend their availability space.

An injectable and conductive TEMPOL/polypyrrole integrated peptide co-assembly hydrogel promotes functional maturation of cardiomyocytes for myocardial infarction repair

A cell-implantation strategy offers a promising paradigm for cardiac repair after myocardial infarction (MI). However, the hostile reactive oxygen species (ROS) microenvironment in infarcted zone hinders the survival and maturation of implanted cells and affects the ultimate therapeutic outcome. Besides, the generation of fibrosis scarring deprives the myocardium of electrical communications and induces cardiac dysfunction, eventually resulting in heart failure. Herein, an injectable ROS-scavenging/conductive composite hydrogel (R&C-Gel) was constructed via specific binding between conductive polypyrrole (PPy) and multi-component co-assembly peptides. Integrating antioxidant TEMPOL into the peptide endows it with strong ROS-eliminating ability, and the nanoengineering of polypyrrole (PPy) by wet milling facilitates PPy uniformly binding to the target T59 peptide in nanofibers . The thixotropy of co-assembly hydrogels confirmed by rheology and the macroporous structure of the R&C-Gel surface observed by SEM together suggest that the R&C-Gel could be an ideal vehicle for cell engraftment. The antioxidant ability and electroconductivity of the R&C-Gel were verified. In vitro experiments demonstrated that the R&C-Gel could efficiently remove ROS in cardiomyocytes and reduce apoptosis under oxygen-glucose deprivation (OGD) conditions. The rhythmic intracellular Ca 2+ puffs and expression of Cx-43 protein further proved the R&C-Gel could enhance the electrical and contractile performance of cardiomyocytes. Echocardiography and histological analysis convincingly revealed that the R&C-Gel-combined cardiomyocytes significantly promoted cardiac repair and rebuilt cardiac function, such as reducing apoptosis, accelerating gap junction formation , increasing ejection fraction , and decreasing the fibrosis area. This study provides new insight into the design and construction of multifunctional conductive hydrogels for cardiac tissue engineering . • An injectable composite hydrogel (R&C-Gel) is prepared via specific binding between conductive PPy and multi-component peptides. • Integrating the TEMPOL endows the R&C-Gel with strong ROS-eliminating ability to reduce the apoptosis of CMs under hypoxia. • Nanoengineering of vapor-polymerized PPy membrane to conductive NanoClusters facilitates PPy uniformly binding to nanofibers of R&C-gel. • R&C-Gel promotes rhythmic intracellular Ca 2+ puffs and the expression of Cx-43 protein in the maturation of CMs. • Injection of CMs@R&C-Gel is capable of restoring cardiac function post-MI.

Peptide Coassembly to Enhance Piezoelectricity for Energy Harvesting.

The discovery of piezoelectricity in self-assembled peptide nanostructures opens an avenue to a new regime of piezoelectric materials and enables the fundamental investigation of electromechanical coupling in biomaterials. However, strategies for fabricating peptides with desired properties are still lacking. We find that a peptide-based coassembly process effectively controls the properties of peptide nanomaterials and demonstrates their application potential in nanogenerators. The composing peptides and their concentration influence the morphology, molecular property, and physical property of coassembled crystals. Compared with self-assembled diphenylalanine peptides, the coassembled peptides of diphenylalanine and phenylalanine-tryptophan show a 38% increase in piezoelectric coefficient, and the resulting harvesting device shows nearly a 3-fold increase in open-circuit voltage outputs.

Engineering β-Sheet Peptide Coassemblies for Biomaterial Applications.

Peptide coassembly, wherein at least two different peptides interact to form multicomponent nanostructures, is an attractive approach for generating functional biomaterials. Current efforts seek to design pairs of peptides, A and B, that form nanostructures (e.g., β-sheets with ABABA-type β-strand patterning) while resisting self-assembly (e.g., AAAAA-type or BBBBB-type β-sheets). To confer coassembly behavior, most existing designs have been based on highly charged variants of known self-assembling peptides; like-charge repulsion limits self-assembly while opposite-charge attraction promotes coassembly. Recent analyses using solid-state NMR and coarse-grained simulations reveal that preconceived notions of structure and molecular organization are not always correct. This perspective highlights recent advances and key challenges to understanding and controlling peptide coassembly.

Co-assembly of Peptides and Carbon Nanodots: Sensitive Analysis of Transglutaminase 2.

The structures assembled by peptides have attracted great attention due to their unique physicochemical properties. Moreover, the co-assembly of peptides with additional components can endow the structures with extended functions. In this work, we have explored the co-assembly of peptides and carbon nanodots (CNDs) by taking advantage of their non-covalent binding; thus, the obtained structure may show both the recognition capability of peptides and the catalytic activity of CNDs. Therefore, we have further used the assembled structure for the sensitive analysis of transglutaminase 2 with a low detection limit of 0.25 pg/mL. By simply replacing the peptide sequences or the nanomaterials, the strategy proposed in this work can be developed as a universal model to build the co-assemblies of peptides and nanomaterials, thus leading to their broader applications in biological and biomedical research.

Supramolecular co-assembly of self-adjuvanting nanofibrious peptide hydrogel enhances cancer vaccination by activating MyD88-dependent NF-κB signaling pathway without inflammation

Peptide vaccine targeting tumor-specific antigens is a promising cancer treatment regimen. However, peptide vaccines are commonly low-immunogenic, leading to suboptimal antitumor T-cell responses. Current peptide vaccination approaches are challenged by the variability of peptide physicochemical characters and vaccine formulations, flexibility, and the broad feasibility. Here, the supramolecular co-assembly of antigen epitope-conjugated peptides (ECPs) targeting CD8 or CD4 T-cell receptors was used to engineer a nanofibrious hydrogel vaccine platform. This approach provided precise and tunable loading of peptide antigens in nanofibers, which notably increased the antigen uptake, cross-presentation, and activation of dendritic cells (DCs). Immunization in mice indicated that the co-assembled peptide hydrogel did not induce local inflammation responses and elicited significantly promoted T-cell immunity by activating the MyD88-dependent NF-κB signaling pathway in DCs. Vaccination of mice using co-assembled peptide vaccine stimulated both enhanced CD8 and CD4 T cells against EG.7-OVA tumors without additional immunoadjuvants or delivery systems, and resulted in a more remarkable cancer immunotherapy efficacy, compared with free peptide vaccine or aluminum-adjuvanted peptide formulation. Altogether, peptide co-assembly demonstrated by three independent pairs of ECPs is a facile, customizable, and chemically defined approach for co-delivering peptide antigens in self-adjuvanting hydrogel vaccines that could induce stronger anticancer T-cell responses.

Peptide-Peptide Co-Assembly: A Design Strategy for Functional Detection of C-peptide, A Biomarker of Diabetic Neuropathy.

Diabetes-related neuropathy is a debilitating condition that may be averted if it can be detected early. One possible way this can be achieved at low cost is to utilise peptides to detect C-peptide, a biomarker of diabetic neuropathy. This depends on peptide-peptide co-assembly, which is currently in a nascent stage of intense study. Instead, we propose a bead-based triple-overlay combinatorial strategy that can preserve inter-residue information during the screening process for a suitable complementary peptide to co-assemble with C-peptide. The screening process commenced with a pentapeptide general library, which revealed histidine to be an essential residue. Further screening with seven tetrapeptide focused libraries led to a table of self-consistent peptide sequences that included tryptophan and lysine at high frequencies. Three complementary nonapeptides (9mer com-peptides), wpkkhfwgq (Trp-D), kwkkhfwgq (Lys-D), and KWKKHFWGQ (Lys-L) (as a negative control) were picked from this table for co-assembly studies with C-peptide. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) and circular dichroism (CD) spectroscopies were utilized to study inter-peptide interactions and changes in secondary structures respectively. ATR-FTIR studies showed that there is indeed inter-peptide interaction between C-peptide and the tryptophan residues of the 9mer com-peptides. CD studies of unaggregated and colloidal C-peptide with the 9mer com-peptides suggest that the extent of co-assembly of C-peptide with Trp-D is greatest, followed by Lys-D and Lys-L. These results are promising and indicate that the presented strategy is viable for designing and evaluating longer complementary peptides, as well as complementary peptides for co-assembly with other polypeptides of interest and importance. We discuss the possibility of designing complementary peptides to inhibit toxic amyloidosis with this approach.

Self-assembled supramolecular nanostructure photosensitizers for photocatalytic hydrogen evolution

Supramolecular self-assembly as a breakthrough methodology in the nanoscience and nanotechnology fields has attracted increasing attention. Highly ordered self-assembled supramolecular nanostructures aim to emulate natural light-harvesting and energy transfer and electron transfer processes, which have been an active and rapidly developing field for visible-light-driven photocatalytic applications. This Research Update aims to present the recent progress of the self-assembly of π-conjugated molecules, including perylene diimides (PDIs), porphyrin, and co-assembly of peptide–porphyrin as well as the shape-defined functional hierarchical structures. First, the basic principles of π-conjugated molecular structure design are described. The two nitrogen positions and the bay positions of PDIs can effectively regulate their electronic properties and geometric skeleton, and the functional groups and the good solvents of porphyrin effectively determine the choice of self-assembly methods. Then, the key morphology dependent optoelectronic properties and charge-transport and energy-transport functionalities are also discussed. These self-assembled supramolecular nanostructures’ inherent optoelectronic properties correlated with applications in photocatalytic water splitting into hydrogen evolution are overviewed. By now, the self-assembled In(III) meso-tetraphenylporphine (InTPP) porphyrin nanostructures exhibited the highest photocatalytic hydrogen generation activity among the reported supramolecular nanostructures owing to the central metal of porphyrin and small size of the InTPP nanostructure. Finally, perspectives on the crucial issues and potential future research directions are addressed. This Research Update will provide a new reference for building high performance, stable, and durable photosensitizers based on the supramolecular assembly.

Charge guides pathway selection in \u03b2-sheet fibrillizing peptide co-assembly

Peptide co-assembly is attractive for creating biomaterials with new forms and functions. Emergence of these properties depends on the peptide content of the final assembled structure, which is difficult to predict in multicomponent systems. Here using experiments and simulations we show that charge governs content by affecting propensity for self- and co-association in binary CATCH(+/−) peptide systems. Equimolar mixtures of CATCH(2+/2−), CATCH(4+/4−), and CATCH(6+/6−) formed two-component β-sheets. Solid-state NMR suggested the cationic peptide predominated in the final assemblies. The cationic-to-anionic peptide ratio decreased with increasing charge. CATCH(2+) formed β-sheets when alone, whereas the other peptides remained unassembled. Fibrillization rate increased with peptide charge. The zwitterionic CATCH parent peptide, “Q11”, assembled slowly and only at decreased simulation temperature. These results demonstrate that increasing charge draws complementary peptides together faster, favoring co-assembly, while like-charged molecules repel. We foresee these insights enabling development of co-assembled peptide biomaterials with defined content and predictable properties.

Polystyrene-block-poly(ethylene oxide) Thin Films Fabricated from a Solvent Mixture for the Co-Assembly of Polymers and Proteins.

The co-assembly of peptides and proteins in poly(styrene-block-ethylene oxide) (PS-b-PEO) thin films has proven to be a promising method to fabricate polymer–biomolecule functional materials. Contrary to the covalent immobilization of biomolecules on surfaces, co-assembly presents the opportunity to arrange cargo within thin films, which can be released upon exposure to an aqueous environment. The use of a mixed solvent system ensures the solubilization of hydrophobic polymer as well as the solubilization and protection of the biomolecule cargo. However, to produce largely defect-free films of PS-b-PEO from a solvent mixture containing water is challenging due to the narrow range of solvent miscibility and polymer/protein solubility. This work explores the limits of using a benzene/methanol/water solvent mixture for the production of thin PS-b-PEO films and provides a template for the fabrication optimization of block copolymer thin films in different complex solvent systems. The film quality is analyzed using optical microscopy and atomic force microscopy and correlated to the solvent composition. By adjusting the solvent composition to 80/18.8/1.2 vol % benzene/methanol/water, it was possible to reliably fabricate thin films with less than 1% macroscopic defect surface coverage. Using the optimized solvent composition, we also demonstrate the fabrication of ordered PS-b-PEO films containing lysozyme. Furthermore, we show the release of lysozyme into aqueous media, which highlights the potential use of such films for drug delivery applications.

Nucleic acids induced peptide-based AIE nanoparticles for fast cell imaging

Herein, we utilized nucleic acids induced peptide co-assembly strategy to develop novel nucleic acids induced peptide-based AIE (NIP-AIE) nanoparticles. Strong fluorescent of AIE could be observed when a little amount of nucleic acids was added into the peptide solution, and the intensity could be regulated by the concentration of nucleic acids. This AIE nanoparticle with good biocompatibility could achieve fast cell imaging. It is also proved that the fluorescence intensity of AIE decreased with time, which indicates that the reducible cross-linkers of Wpc peptide by GSH and nanoparticles gradually disintegrate in cell. Based on the different of AIE fluorescence signals which regulated by the formation and disintegration of nanoparticles, this AIE system is expected to be used for real-time monitoring of drug release from peptide-based nano carriers in vivo or in vitro, and may provide a new platform for the construction of other organic AIE nanoparticles.

Peptides Co-Assembling into Hydrangea-Like Microstructures.

Supramolecular assembly in vitro is a simple and effective way to produce multi-level biostructures to mimic the self-assembly of biomolecules in organisms. The study on peptide assembly behaviors would benefit a lot to understand what goes on in life, as well as in the construction of plenty of functional biomaterials that have potential applications in various fields. Since cellular microenvironments are crowded and contain various biomolecules, studying protein and peptide co-assembly is of great interest. Here, we introduced the co-assembly of 5-FAM-ELVFFAE-NH₂ (EE-7) and (CY5)-KLVFFAK-NH₂ (KK-7), which are sequences derived from the core of the amyloid β (Aβ) peptide, a key protein in Alzheimer's diseases. Morphologic studies employing atomic force microscopy and scanning electron microscopy indicated that the co-assembled entities had a novel hydrangea-like microstructure, in contrast to micro-sheet structures formed from monocomponent EE-7 or KK-7, respectively. Fluorescence co-localization experiments confirmed that the hydrangealike microstructures were indeed made of both EE-7 and KK-7. We suggest that the formation of the hydrangea-like microstructures is driven by both the electrostatic and hydrophobic interactions between EE-7 and KK-7. A molecular mechanism has been provided to explain the formation of the hydrangea-like microstructures.

Protamine-induced condensation of peptide nanofilaments into twisted bundles with controlled helical geometry.

Chiral self-assembly of peptides is of fundamental interest in the field of biology and material science. Protamine, an alkaline biomacromolecule which is ubiquitous in fish and mammalian, plays crucial roles in directing the helical twisting of DNA. Inspired by this, we reported a bioinspired pathway to direct the hierarchical chiral self-assembly of a short synthetic dipeptide. The peptide could self-assemble into negatively charged chiral micelles in water that spontaneously formed a nematic liquid crystalline phase. By incorporation with protamine, the micelles condensed with the protamine into large helical bundles with precisely controlled diameter. Furthermore, to simulate the intracellular environments, we investigated macromolecular crowding on the coassembly of peptide and protamine, which leads to the formation of much thinner helical structures. The results highlight the roles of highly charged biomacromolecules and macromolecular crowding on peptide self-assembly, which are beneficial for the practical applications of self-assembling peptides in biomedicine and sensing.