Unexpected Role of Achiral Glycine in Determining the Suprastructural Handedness of Peptide Nanofibrils

Effects of reduced graphene oxide nanomaterials on transformation of 14C-triclosan in soils

Increasing use and release of graphene nanomaterials and pharmaceutical and personal care products (PPCPs) in soil environment have polluted the environment and posed high ecological risks. However, little is understood about the interactive effects and mechanism of graphene on the behaviors of PPCPs in soil. In the present study, the effects of reduced graphene oxide nanomaterials (RGO) on the fate of triclosan in two typical soils (S1: silty loam; S2: silty clay loam) were investigated with 14C-triclosan, high-resolution mass spectrometry, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), density functional theory (DFT) calculations, and microbial community structure analysis. The results showed that RGO prolonged the half-life of triclosan by 23.6-51.3 %, but delayed the formation of transformed products such as methyl triclosan and dechlorinated dimer of triclosan in the two typical soils. Mineralization of triclosan to 14CO2 was inhibited by 48.2-79.3 % in 500 mg kg-1 RGO in comparison with that in the control, whereas the bound residue was 54.2-56.4 % greater than the control. RGO also reduced the relative abundances of triclosan-degrading bacteria (Pseudomonas and Sphingomonas) in soils. Compared to silty loam, RGO more effectively inhibited triclosan degradation in silty clay loam. Furthermore, the DFT calculations suggested a strong association of the adsorption of triclosan on RGO with the van der Waals forces and π-π interactions. These results revealed that RGO inhibited the transformation of 14C-triclosan in soil through strong adsorption and triclosan-degrading bacteria inhibition in soils. Therefore, the presence of RGO may potentially enhance persistence of triclosan in soil. Overall, our study provides valuable insights into the risk assessment of triclosan in the presence of GNs in soil environment.

Molecular Dynamics Analysis of Surface-Modified Carbon Nanoparticle Reinforced Epoxy Resin

Surface-modified carbon nanoparticles (CNPs) as reinforcement materials have attracted significant attention due to their potential for substantially enhancing mechanical properties. However, the development and application of CNP-enhanced polymeric materials are constrained by an incomplete understanding of their reinforcement mechanisms, impeding sustainable progress. In this study, we employed molecular dynamics simulations to investigate the mechanical properties of surface-modified CNP-reinforced epoxy resin composites at the microscopic scale. The simulations focused on the tensile process and the nanopinning effect of CNPs within the epoxy resin matrix. Our results indicate that surface-modified CNPs form stronger interfacial connections with the epoxy resin, leading to enhanced mechanical strength of the composites. Quantitative analysis revealed that these composites exhibit higher tensile strength compared to nonmodified counterparts, with a significant improvement in stability due to the robust noncovalent interactions between CNPs and the epoxy matrix. This study elucidates the reinforcement mechanisms of surface-modified CNPs in polymers, providing valuable insights for further optimization and sustainable development of CNP-reinforced polymeric materials.

Mineralized aggregates based on native protein phase transition for non-destructive diagnosis of seborrheic skin by surface-enhanced Raman spectroscopy

The non-homeostasis of sebum secretion by the sebaceous glands in a complicated microenvironment dramatically impacts the skin health of many people in the world. However, the complexity and hydrophobicity of sebum mean a lack of diagnostic tools, which makes it challenging to determine the reason behind cortical imbalances. Herein, a biomimetic mineralized aggregates (PTL@Au and PTB@Au) strategy has been proposed, which could obtain molecular information about sebum by surface-enhanced Raman spectroscopy (SERS). The breaking of disulfide bonds leads to changes in hydrogen bonding, which transform the natural protein into amyloid-like phase transition protein with β-sheets. It provides sites for the nucleation and crystallization of gold nanocrystals to build mineralized aggregates. The mineralized aggregates show robust adhesion stability at the interfaces of different materials through hydrogen bonding and electrostatic interactions. The stabilization, hydrophobicity (contact angle: 134°), and optical transmission (75%) of the structure could result in superior SERS performance for sebum analysis. It should be noted that this enables the sebum detection of clinical samples while ensuring safety. Such generalized bionic mineralization construction and diagnosis methods also serve as an advanced paradigm for a range of biomedical applications.

Recent progress in quantitative analysis of self-assembled peptides

Self-assembled peptides have been among the important biomaterials due to its excellent biocompatibility and diverse functions. Over the past decades, substantial progress and breakthroughs have been made in designing self-assembled peptides with multifaceted biomedical applications. The techniques for quantitative analysis, including imaging-based quantitative techniques, chromatographic technique and computational approach (molecular dynamics simulation), are becoming powerful tools for exploring the structure, properties, biomedical applications, and even supramolecular assembly processes of self-assembled peptides. However, a comprehensive review concerning these quantitative techniques remains scarce. In this review, recent progress in techniques for quantitative investigation of biostability, cellular uptake, biodistribution, self-assembly behaviors of self-assembled peptide etc., are summarized. Specific applications and roles of these techniques are highlighted in detail. Finally, challenges and outlook in this field are concluded. It is believed that this review will provide technical guidance for researchers in the field of peptide-based materials and pharmaceuticals, and facilitate related research for newcomers in this field.

Chiral inversion induced by aromatic interactions in short peptide assembly

Although hydrophobic interactions provide the main driving force for initial peptide aggregation, their role in regulating suprastructure handedness of higher-order architectures remains largely unknown. We here interrogate the effects of hydrophobic amino acids on handedness at various assembly stages of peptide amphiphiles. Our studies reveal that relative to aliphatic side chains, aromatic side chains set the twisting directions of single β-strands due to their strong steric repulsion to the backbone, and upon packing into multi-stranded β-sheets, the side-chain aromatic interactions between strands form the aromatic ladders with a directional preference. This ordering not only leads to parallel β-sheet arrangements but also induces the chiral flipping over of single β-strands within a β-sheet. In contrast, the lack of orientational hydrophobic interactions in the assembly of aliphatic peptides implies no chiral inversion upon packing into β-sheets. This study opens an avenue to harness peptide aggregates with targeted handedness via aromatic side-chain interactions.

What happens when left meets right under equimolar and non-equimolar co-assembly of short peptide stereoisomers?

The co-assembly of different peptide chains usually leads to the formation of intricate architectures and sophisticated functions in biological systems. Although the co-assembly of stereoisomeric peptides represents a facile and flexible strategy for the synthesis of peptide-based nanomaterials with novel structures and potentially interesting properties, there is a lack of a general knowledge on how different isomers pack during assembly. Through the combined use of simulations and experimental observations, we report that heterochiral pairing is preferred to homochiral pairing at the molecular scale but self-sorting dictates beyond the molecular level for the mixtures of the short stereoisomeric β-sheet peptides I3K (Ile-Ile-Ile-Lys). Furthermore, we demonstrate that flat β-sheets and fibril morphology are always preferred to twisted ones during heterochiral pairing and subsequent assembly. However, the heterochiral pairing into flat morphology is not always at an equimolar ratio. Instead, a non-equimolar ratio (1:2) is observed for the mixing of homochiral LI3LK and heterochiral LI3DK, whose strand twisting degrees differ greatly. Such a study provides a paradigm for understanding the co-assembly of stereoisomeric peptides at the molecular scale and harnessing their blending for targeted nanostructures.

Photoisomerization and thermal reconstruction induced supramolecular chirality inversion in nanofiber determined by minority isomer

Here, amphiphile GCH based on glutamide-cyanostilbene is designed and synthesized, it is found that it can assembly in acetonitrile, and shows circular dichroism signals. After Z-E isomerizaition by UV irradiation, the CD signal of the assembly can be inverted. Unexpectedly, after another heating and cooling process, the circular dichroism signals can be totally inverted even though the E-isomers are in minority. Finally, the molecular dynamics (MD) simulations deeply elucidate the supramolecuar chirality inversion mechanism. This work brings some new insights into the control of chirality inversion, which may provide a perspective for the smart chiroptical materials construction.

Controlling 1D Nanostructures and Handedness by Polar Residue Chirality of Amphiphilic Peptides

Peptide assemblies are promising nanomaterials, with their properties and technological applications being highly hinged on their supramolecular architectures. Here, how changing the chirality of the terminal charged residues of an amphiphilic hexapeptide sequence Ac-I4 K2 -NH2 gives rise to distinct nanostructures and supramolecular handedness is reported. Microscopic imaging and neutron scattering measurements show thin nanofibrils, thick nanofibrils, and wide nanotubes self-assembled from four stereoisomers. Spectroscopic and solid-state nuclear magnetic resonance (NMR) analyses reveal that these isomeric peptides adopt similar anti-parallel β-sheet secondary structures. Further theoretical calculations demonstrate that the chiral alterations of the two C-terminal lysine residues cause the formation of diverse single β-strand conformations, and the final self-assembled nanostructures and handedness are determined by the twisting direction and degree of single β-strands. This work not only lays a useful foundation for the fabrication of diverse peptide nanostructures by manipulating the chirality of specific residues but also provides a framework for predicting the supramolecular structures and handedness of peptide assemblies from single molecule conformations.

Surface Engineering of Migratory Corrosion Inhibitors: Controlling the Wettability of Calcium Silicate Hydrate in the Nanoscale

Migratory corrosion inhibitors (MCIs) are regarded as effective additives to prevent harmful ion transmission and improve concrete durability, but their behavior in the porosity of concrete is still unclarified. This paper proposes a unique perspective to evaluate the effects of surfactant-like MCIs in calcium silicate hydrate (C-S-H) nanoporosity through molecular and electronic structural information. Advanced enhanced sampling methods and perturbation theory methods were applied to evaluate the role of different MCIs. The reduced density gradient of MCI molecules was obtained by using quantum chemical calculations. This calculation is instrumental in elucidating the intensity of interactions among distinct MCI molecule head groups and the C-S-H matrix. It is found that MCIs can effectively improve the interfacial tension (IFT) between C-S-H and water, which corresponds to the inhibitory ability of transmission. Free energy indicates that the MCI has the properties of strong adsorption and weak dissolution, facilitating the improvement of IFT. The relationship between the MCI functional group and the ability of adsorption and dissolution is revealed. This study suggests that MCIs work as surface controllers of C-S-H pores and that their properties can be assessed on the nanoscale.

Multi-stage adsorption of methyl orange on the nitrogen-rich biomass-derived carbon adsorbent: DFT and MD evaluation

Dyes that are released into the environment may have negative effects on living organisms. To address this issue, a biomass-derived carbon adsorbent made from Enteromorpha was tested for its ability to remove methyl orange (MO) from wastewater. The adsorbent was found to be effective in removing MO, with a 1:4 impregnation ratio producing an adsorbent that could remove 96.34% of MO from a 200 mg/L solution using only 0.1 g of adsorbent. At higher concentrations, the adsorption capacity increased up to 269.58 mg/g. Through molecular dynamics simulations, it was discovered that after mono-layer adsorption reached saturation, the remaining MO molecules in solution formed hydrogen bonds with the adsorbed MO, which led to further aggregation on the adsorbent surface and increased adsorption capacity. Additionally, theoretical investigations revealed that the adsorption energy of anionic dyes increased with Nitrogen-doped carbon materials, with the pyrrolic-N site having the highest adsorption energy for MO. The carbon material derived from Enteromorpha showed promise in treating wastewater containing anionic dyes, thanks to its high adsorption capacity and strong electrostatic interaction with the sulfonic acid groups of MO.

Green Synthesis and Bioactivity of Aliphatic N-Substituted Glycine Derivatives

Standard amino acids have an asymmetric α-carbon atom to which -COOH, -NH2, -H, and -R groups are bonded. Among them, glycine is the simplest (R = -H) with no asymmetric carbon, and other natural amino acids are C-substituted of glycine. Here, we have designed and made a green synthesis of some new N-substituted glycine derivatives with R-(NH)CH2-COOH formula, where R is flexible and hydrophobic with different chain lengths and benches of the type propyl, butyl, sec-butyl, tert-butyl, pentyl, isopentyl, tert-pentyl, hexyl, 2-aminoheptyl, and octyl. These glycine derivatives were characterized by recording their melting points and FT-IR, mass, 1H NMR, and 13C NMR spectra. DFT studies revealed that 2-aminoheptyl glycine had the highest electronegativity value and can thus act as a good bidentate ligand for the metal centers. ADME comparative results and bioavailability radars indicated that both octyl- and 2-aminoheptyl glycine had the most lipophilicity, making them good agents in cell passing. Furthermore, lipophilicity determination showed that octyl glycine was the best and propylgly was more soluble than others. Based on solubility, lipophilicity, and dipole moment values, propyl- and 2-aminoheptyl-glycine were considered for bio-macromolecular interaction studies. Thus, the interaction of these two agents with DNA and HSA was studied using absorption spectroscopy and circular dichroism techniques. Due to the presence of the R-amine group, they can interact with the DNA by H-binding and hydrophobicity, while electrostatic mode could not be ruled out. Meanwhile, molecular docking studies revealed that octyl- and 2-aminoheptyl glycine had the highest negative docking energy, which reflects their higher tendency to interact with DNA. The DNA binding affinity of two candidate AAs was determined by viscosity measurement and fluorescence emission recording, which confirms that groove binding occurs. Also, the toxicity of these synthesized amino acid derivates was tested against the human foreskin fibroblast (HFF) cell line. They showed IC50 values within the range of 127-344 μM after 48 h with the highest toxicity for 2-aminoheptyl glycine.

Effect of Achiral Glycine Residue on the Handedness of Surfactant-Like Short Peptide Self-Assembly Nanofibers

Surfactant-like short peptides are a kind of ideal model for the study of chiral self-assembly. At present, there are few studies on the chiral self-assembly of multicharged surfactant-like peptides. In this study, we adopted a series of short peptides of Ac-I₄KGK-NH₂ with different combinations of L-lysine and D-lysine residues as the model molecules. TEM, AFM and SANS results showed that Ac-I₄^LKG^LK-NH₂, Ac-I₄^LKG^DK-NH₂, and Ac-I₄^DKG^LK-NH₂ formed the morphologies of nanofibers, and Ac-I₄^DKG^DK-NH₂ formed nanoribbons. All the self-assembled nanofibers, including the intermediate nanofibers of Ac-I₄^DKG^DK-NH₂ nanoribbons, showed the chirality of left handedness. Based on the molecular simulation results, it has been demonstrated that the supramolecular chirality was directly dictated by the orientation of single β strand. The insertion of glycine residue demolished the effect of lysine residues on the single strand conformation due to its high conformational flexibility. The replacement of L-isoleucine with Da-isoleucine also confirmed that the isoleucine residues involved in the β-sheet determined the supramolecular handedness. This study provides a profound mechanism of the chiral self-assembly of short peptides. We hope that it will improve the regulation of chiral molecular self-assembly with achiral glycine, as well.

Probing Molecular Chirality on the Self-Assembly and Gelation of Naphthalimide-Conjugated Dipeptides

In this work, 1,8-naphthalimide (NMI)-conjugated three hybrid dipeptides constituted of a β-amino acid and an α-amino acid have been designed, synthesized, and purified. Here, in the design, the chirality of the α-amino acid was varied to study the effect of molecular chirality on the supramolecular assembly. Self-assembly and gelation of three NMI conjugates were studied in mixed solvent systems [water and dimethyl sulphoxide (DMSO)]. Interestingly, chiral NMI derivatives [NMI-βAla-^lVal-OMe (NLV) and NMI-βAla-^dVal-OMe (NDV)] formed self-supported gels, while the achiral NMI derivative [NMI-βAla-Aib-OMe, (NAA)] failed to form any kind of gel at 1 mM concentration and in a mixed solvent (70% water in DMSO medium). Self-assembly processes were thoroughly investigated using UV-vis spectroscopy, nuclear magnetic resonance (NMR), fluorescence, and circular dichroism (CD) spectroscopy. A J-type molecular assembly was observed in the mixed solvent system. The CD study indicated the formation of chiral assembled structures for NLV and NDV, which were mirror images of one another, and the self-assembled state by NAA was CD-silent. The nanoscale morphology of the three derivatives was studied using scanning electron microscopy (SEM). In the case of NLV and NDV, left- and right-handed fibrilar morphologies were observed, respectively. In contrast, a flake-like morphology was noticed for NAA. The DFT study indicated that the chirality of the α-amino acid influenced the orientation of π-π stacking interactions of naphthalimide units in the self-assembled structure that in turn regulated the helicity. This is a unique work where molecular chirality controls the nanoscale assembly as well as the macroscopic self-assembled state.

Kinetic Controlled Chirality Transfer and Induction in 2D Hydrogen-Bonding Assemblies of Glycylglycine on Au(111)

Chirality transfer is of vital importance that dominates the structure and functionality of biological systems and living matters. External physical stimulations, e.g. polarized light and mechanical forces, can trigger the chirality symmetry breaking, leading to the appearance of the enantiomeric entities created from a chiral self-assembly of achiral molecule. Here, several 2D assemblies with different chirality, synthesized on Au(111) surface by using achiral building blocks - glycylglycine (digly), the simplest polypeptide are reported. By delicately tuning the kinetic factors, i.e., one-step slow/rapid deposition, or stepwise slow deposition with mild annealing, achiral square hydrogen-bond organic frameworks (HOF), homochiral rhombic HOF and racemic rectangular assembly are achieved, respectively. Chirality induction and related symmetry broken in assemblies are introduced by the handedness (H-bond configurations in principle) of the assembled motifs and then amplified to the entire assemblies via the interaction between motifs. The results show that the chirality transfer and induction of biological assemblies can be tuned by altering the kinetic factors instead of applying external forces, which may offer an in-depth understanding and practical approach to peptide chiral assembly on the surfaces and can further facilitate the design of desired complex biomolecular superstructures.

Two dimensional (2D) materials and biomaterials for water desalination; structure, properties, and recent advances

BACKGROUND

An efficient solution to the global freshwater dilemma is desalination. MXene, Molybdenum Disulfide (MoS₂), Graphene Oxide, Hexagonal Boron Nitride, and Phosphorene are just a few examples of two-dimensional (2D) materials that have shown considerable promise in the development of 2D materials for water desalination. However, other promising materials for desalinating water are biomaterials. The benefits of bio-materials are their wide distribution, lack of toxicity, and superior capacity for water desalination.

METHODS

For the rational use of water and the advancement of sustainable development, it is of the utmost importance to research 2D-dimensional materials and biomaterials that are effective for water desalination. The scientific community has concentrated on wastewater remediation using bio-derived materials, such as nanocellulose, chitosan, bio-char, bark, and activated charcoal generated from plant sources, among the various endeavors to enhance access to clean water. Moreover, the 2D-materials and biomaterials may have ushered in a new age in the production of desalination materials and created a promising future.

RESULTS

The present review article focuses on and reviews the progress of 2D materials and biomaterials for water desalination. Their properties, surface, and structure, combined with water desalination applications, are highlighted. Further, the practicability and potential future directions of 2D materials and biomaterials are proposed. Thus, the current work provides information and discernments for developing novel 2D materials and biomaterials for wastewater desalination. Moreover, it aims to promote the contribution and advancement of materials for water desalination, fabrication, and industrial production.

Achiral organoiodine-functionalized helical polyisocyanides for multiple asymmetric dearomative oxidations

Immobilizing organocatalyst onto helical polymers not only facilitates the catalyst recycling from homogeneous reactions, but also boosts enantioselectivity. In this work, achiral organoiodine-functionalized single left- and right-handed helical polyisocyanides were prepared from the same monomers, which catalyzed three asymmetric oxidations gave the desired products in high yields and excellent enantioselectivity. The enantiomeric excess of the target products was up to 95%. Remarkably, the enantioselectivity can be switched by reversing the helicity of the polymer backbone. The polymer catalysts can be facilely recovered and recycled in different asymmetric oxidations with maintained excellent activity and enantioselectivity.

Tuning of the Supramolecular Helicity of Peptide-Based Gel Nanofibers

Helical supramolecular architectures play important structural and functional roles in biological systems. The helicity of synthetic molecules can be tuned mainly by the chiral manipulation of the system. However, tuning of helicity by the achiral unit of the molecules is less studied. In this work, the helicity of naphthalimide-capped peptide-based gel nanofibers is tuned by the alteration of methylene units present in the achiral amino acid. The inversion of supramolecular helicity has been extensively studied by CD spectroscopy and morphological analysis. The density functional theory (DFT) study indicates that methylene spacers influence the orientation of π-π stacking interactions of naphthalimide units in the self-assembled structure that regulates the helicity. This work illustrates a new approach to tuning the supramolecular chirality of self-assembled biomaterials.

Tuning the shell structure of peptide nanotubes with sodium tartrate: From monolayer to bilayer

Though the function of peptide based nanotubes are well correlated with its shape and size, controlling the dimensions of nanotubes still remains a great challenge in the field of peptide self-assembly. Here, we demonstrated that the shell structure of nanotubes formed by a bola peptide Ac-KI₃VK-NH₂ (KI₃VK, in which K, I, and V are abbreviations of lysine, isoleucine, and valine) can be regulated by mixing it with the salt sodium tartrate (STA). The ratio of KI₃VK and STA had a great impact on shell structure of the nanotubes. Bilayer nanotubes can be constructed when the molar ratio of KI₃VK and STA was less than 1:2. Both the two hydroxyls and the negative charges carried by STA were proved to play important roles in the bilayer nanotubes formation. Observations of different intermediates provided obvious evidence for the varied pathway of the bilayer nanotubes formation. Based on these experimental results, the possible mechanism for bilayer nanotubes formation was proposed. Such a study provides a simple and effective way for regulating the shell structure of the nanotubes and may expand their applications in different fields.

Inversion of Supramolecular Chirality by In Situ Hydrolyzation of Achiral Diethylene Glycol Motifs

Chiral inversion of supramolecular assemblies is of great research interest due to its broad practical applications. However, chiral structure transition induced by in situ regulation of building molecules has remained a challenge. Herein, left-handed fibrous assemblies were constructed by C₂-symmetic l-phenylalanine coupled with diethylene glycol (LPFEG) molecules. In situ hydrolyzing terminal diethylene glycol motifs in LPFEG successfully inverted the chirality of the nanofibers from left- to right-handedness. The transition of right-handed fibers into left-handed fibers could also be achieved via hydrolyzing DPFEG molecules. Circular dichroism (CD) spectroscopy, 1D and 2D nuclear magnetic resonance (NMR) spectroscopy, and Fourier transform infrared (FT-IR) spectroscopy revealed that the back-folded achiral diethylene glycol played a vital role in L/DPFEG molecular arrangements and removing terminal diethylene glycol could induce the opposite rotation of molecular assemblies. Thanks to this merit, the enantioselective separation of racemic phenylalanine was obtained and the enantiomeric excess (ee) values could achieve around ±20% after separation. This study not only provides a new strategy to regulate the chiral structure via dynamic modulation of terminal substituents but also presents a promising application in the field of enantioselective separation.

Molecular Insight into the β-Sheet Twist and Related Morphology of Self-Assembled Peptide Amphiphile Ribbons

Self-assembly of high-aspect-ratio filaments containing β-sheets has attracted much attention due to potential use in bioengineering and biomedicine. However, precisely predicting the assembled morphologies remains a grand challenge because of insufficient understanding of the self-assembly process. We employed an atomistic model to study the self-assembly of peptide amphiphiles (PAs) containing valine-glutamic acid (VE) dimeric repeats. By changing of the sequence length, the assembly morphology changes from flat ribbon to left-handed twisted ribbon, implying a relationship between β-sheet twist and strength of interstrand hydrogen bonds. The calculations are used to quantify this relationship including both magnitude and sign of the ribbon twist angle. Interestingly, a change in chirality is observed when we introduce the RGD epitope into the C-terminal of VE repeats, suggesting arginine and glycine's role in suppressing right-handed β-sheet formation. This study provides insight into the relationship between β-sheet twist and self-assembled nanostructures including a possible design rule for PA self-assembly.