Binary Complex Research Articles

Photo‐Stimuli Smart Supramolecular Self‐Assembly of Azobenzene/β‐Cyclodextrin Inclusion Complex for Controlling Plant Bacterial Diseases

AbstractControllable and on‐demand delivery of supramolecular systems have received considerable attention in modern agricultural management, especially for managing intractable plant diseases. Here, an intelligent photoresponsive pesticide delivery system is reported based on β‐cyclodextrin (β‐CD) and azobenzene, which overcomes the resistance of phytopathogens caused by the irrational use of conventional pesticides. Antibacterial bioassays illustrated that designed azobenzene derivative 3a possesses the most efficient bioactivity with EC50 values of 0.52–25.31 µg mL−1 toward three typical phytopathogens. Moreover, the assembly of the supramolecular binary complex 3a@β‐CD is successfully elucidated and displays exceptional inhibitory activity on biofilm formation. Of note, this supramolecular binary complex significantly improves the water solubility, foliar surface wettability, and shows marked light‐responsive properties. In vivo anti‐Xoo assays reveal that 3a@β‐CD has excellent control efficiency (protective activity: 51.22%, curative activity: 48.37%) against rice bacterial blight pathogens, and their control efficiency can be elevated to values of 55.84% (protective activity) and 52.05% (curative activity) by UV–vis exposure. In addition, the 3a@β‐CD are non‐toxic toward various non‐target organisms. This study therefore offers new insights into the potential of host‐guest complexes as a feasible pesticide discovery strategy characterized by a safe, biocompatible, light‐responsive release, and antibiofilm properties for overcoming intractable plant bacterial diseases.

J-domain Proteins form Binary Complexes with Hsp90 and Ternary Complexes with Hsp90 and Hsp70

Hsp90 and Hsp70 are highly conserved molecular chaperones that help maintain proteostasis by participating in protein folding, unfolding, remodeling and activation of proteins. Both chaperones are also important for cellular recovery following environmental stresses. Hsp90 and Hsp70 function collaboratively for the remodeling and activation of some client proteins. Previous studies using E. coli and S. cerevisiae showed that residues in the Hsp90 middle domain directly interact with a region in the Hsp70 nucleotide binding domain, in the same region known to bind J-domain proteins. Importantly, J-domain proteins facilitate and stabilize the interaction between Hsp90 and Hsp70 both in E. coli and S. cerevisiae. To further explore the role of J-domain proteins in protein reactivation, we tested the hypothesis that J-domain proteins participate in the collaboration between Hsp90 and Hsp70 by simultaneously interacting with Hsp90 and Hsp70. Using E. coli Hsp90, Hsp70 (DnaK), and a J-domain protein (CbpA), we detected a ternary complex containing all three proteins. The interaction involved the J-domain of CbpA, the DnaK binding region of E. coli Hsp90, and the J-domain protein binding region of DnaK where Hsp90 also binds. Additionally, results show that E. coli Hsp90 interacts with E. coli J-domain proteins, DnaJ and CbpA, and that yeast Hsp90, Hsp82, interacts with a yeast J-domain protein, Ydj1. Together these results suggest that the complexes may be transient intermediates in the pathway of collaborative protein remodeling by Hsp90 and Hsp70.

Gene Delivery into T cells using Ternary Complexes of DNA, Lipofectamine, and Carboxy-terminal Phenylalanine-modified Dendrimers.

T-cells play critical roles in various immune reactions, and genetically engineered T-cells have attracted attention for the treatment of cancer and autoimmune diseases. Previously, we showed that a polyamidoamine dendrimer of generation 4 (G4), modified with 1,2-cyclohexanedicarboxylic anhydride (CHex) and phenylalanine (Phe) (G4-CHex-Phe), was useful for delivery into T cells and their subsets. In this study, we constructed an efficient non-viral gene delivery system using this dendrimer. Ternary complexes were prepared using different ratios of plasmid DNA, Lipofectamine, and G4-CHex-Phe. A carboxyl-terminal dendrimer lacking Phe (G3.5) was used for comparison. These complexes were characterized using agarose gel electrophoresis, dynamic light scattering, and ζpotential measurements. In Jurkat cells, the ternary complex with G4-CHex-Phe at a P/COOH ratio of 1/5 showed higher transfection activity than other complexes such as binary and ternary complexes with G3.5 and without any significant cytotoxicity. The transfection efficiency of the G4-CHex-Phe ternary complexes decreased considerably in the presence of free G4-CHex-Phe and on altering the complex preparation method. These results suggest that G4-CHex-Phe promotes the cellular internalization of the complexes, which is useful for gene delivery into T cells. This article is protected by copyright. All rights reserved.

Dynamics of Hydrogen Bond Breaking Induced by Outer-Valence Intermolecular Coulombic Decay

The photoexcitation of weakly bound complexes can lead to several decay pathways, depending on the nature of the potential energy surfaces. Upon excitation of a chromophore in a weakly bound complex, ionization of its neighbor upon energy transfer can occur due to a unique relaxation process known as intermolecular Coulombic decay (ICD), a phenomenon of renewed focus owing to its relevance in biological systems. Herein, we report the evidence for outer-valence ICD induced by multiphoton excitation by near-ultraviolet radiation of 4.4 eV photons, hitherto unknown in molecular systems. In the binary complexes of 2,6-difluorophenylacetylene with aliphatic amines, a resonant two-photon excitation localized on the 2,6-difluorophenylacetylene chromophore results in the formation of an amine cation following an outer-valence ICD process. The unique trends in experimentally observed translational energy distribution profiles of the amine cations following hydrogen bond dissociation, analyzed with the help of electronic structure and ab initio molecular dynamics calculations, revealed the presence of a delicate interplay of roaming dynamics, methyl-rotor dynamics, and binding energy.

A perception into binary and ternary copper (II) complexes: synthesis, characterization, DFT modeling, antimicrobial activity, protein binding screen, and amino acid interaction

Ensuring healthy lives and promoting well-being for all at all ages is the third goal of the sustainable development plan, so it was necessary to identify the most important problems that threaten health in our world. The World Health Organization declared that antibiotic resistance is one of the uppermost global public health threats facing humanity and searching for new antibiotics is slow. This problem can be approached by improving available drugs to combat various bacterial threats. To circumvent bacterial resistance, three copper(II) complexes based on the pefloxacin drug were prepared and characterized using analytical, spectroscopic, and thermal techniques. The resulting data suggested the formation of one octahedral binary and two distorted square pyramidal ternary complexes. Fluorescence spectra results revealed the formation of a turn-on fluorophore for amino acid detection. Computational calculations investigated quantum and reactivity parameters. Molecular electrostatic potential profiles and noncovalent bond interaction-reduced density gradient analysis indicated the active sites on the complex surface. The complexes were subjected to six microbial species, where the octahedral binary complex provoked its antimicrobial potency in comparison with ternary complexes. The enhanced antimicrobial activity against gram-negative bacterium E-coli compared to gentamicin was exhibited by the three complexes. Docking simulation was performed based on the crystal structure of E. coli and S. pneumoniae receptors using 5I2D and 6O15 codes. The binary complex exhibited a potent fitness score with 5I2D (TBE = − 107 kcal/mol) while ternary complexes displayed the highest docked score of fitness with 6O15.

Stability of binary precipitates in Cu-Ni-Si-Cr alloys investigated through active learning

Binary complexes that can be found in copper alloys are investigated in this work through a combination of computer simulations and machine learning. Copper alloys are made of a copper matrix and a combination of single alloying elements in n-ary forms. Due to the coexistence of different types of phases in this matrix, complex regions exist for which information on their precise atomistic structure is missing. In order to uncover such information, we apply active learning and generate moment tensor potentials. This development is based on quantum-mechanical calculations. This approach allows the on-the-fly relaxation of many thousands of potentially novel candidates and check their stability. The ground-state energy of these structures is used to build active learning-generated convex hulls, which are in turn being compared to those from the simulations and the AFLOW database. This procedure provides an insight to additional new stable copper alloy relevant binary complexes. Here, in view of Cu–Ni–Si–Cr alloys, the binary complexes Cu–Si, Ni–Si, Cr–Si, Cr–Ni, Cu–Ni, and Cu–Cr have been investigated. Their stability and the identification of novel stable candidates are discussed based on energetic arguments and the analysis of the respective phonon dispersion. The pipeline followed in this work is able to successfully predict binary phases in Cu–Ni–Si–Cr alloys, specifically for the Cu-Si, Ni–Si, Cr–Ni and Cu–Ni complexes, and to extend the already reported structures in the AFLOW library. In the end, we show the applicability of a predicted Cu–Si stable phase and the developed machine learned potentials at the larger scale of atomistic simulations for the calculation of their mechanical properties and melting behavior. This work provides a computationally efficient framework for material structure prediction and calculation of their properties at a quantum-mechanical accuracy.

Complexation of the Structural Isomers, Propargylimine and Acrylonitrile, with HCN, HNC AND HCP

AbstractA computational study was undertaken of the binary complexes formed by combining HZ (Z=CN, NC, CP) with the structural isomers, acrylonitrile and the Z‐isomer of propargylimine (Z‐PGIM). Two sets of complexes are predicted – hydrogen‐bonded dimers of HZ and acrylonitrile/Z‐PGIM and a set of strongly bound dimers with covalently‐bonded 3‐atom ring(s). The latter dimers were obtained by optimization, starting from an unusual initial configuration, where the atoms of each interacting monomers are in close proximity to each other, and specifically involving an unsaturated bond on, at least, one of the monomers. Seven new dimers were obtained by this procedure and their bonding features were characterized by charge partitioning analyses to rationalize their relative stabilities.

The importance of binding kinetics and drug-target residence time in pharmacology.

A dominant assumption in pharmacology throughout the 20th century has been that in vivo target occupancy-and attendant pharmacodynamics-depends on the systemic concentration of drug relative to the equilibrium dissociation constant for the drug-target complex. In turn, the duration of pharmacodynamics is temporally linked to the systemic pharmacokinetics of the drug. Yet, there are many examples of drugs for which pharmacodynamic effect endures long after the systemic concentration of a drug has waned to (equilibrium) insignificant levels. To reconcile such data, the drug-target residence time model was formulated, positing that it is the lifetime (or residence time) of the binary drug-target complex, and not its equilibrium affinity per se, that determines the extent and duration of drug pharmacodynamics. Here, we review this model, its evolution over time, and its applications to natural ligand-macromolecule biology and synthetic drug-target pharmacology.

Copper-flavonoid family of complexes involved in alkaline phosphatase activation.

The flavonoid naringenin and a family of naringenin derivative Cu(II) complexes having phenanthroline-based second ligands were selected to study alkaline phosphatase activation. This enzyme plays a critical role in tissue formation, increasing the inorganic phosphate formation, favoring mineralization, and being essential to producing bone mineralization. The effects of those compounds on the function and structure of the enzyme were evaluated by kinetic measurements, fluorescence, FTIR, and UV-Vis spectroscopies. The results showed that naringenin did not affect alkaline phosphatase activity, having a value of the Michaelis-Menten-constant close to the enzyme (Km = 3.07 × 10-6). The binary complex, Cu(II)-naringenin, and the ternary complex Cu(II)-naringenin-phenanthroline behaved as an enzyme activator in all the concentrations range used in this study. Those complexes increased in c.a. 1.9% the catalytic efficiency concerning enzyme and naringenin. The ternary complex Cu(II)-naringenin-bathophenanthroline, provokes an activator mixed effect, dependent on the substrate concentrations. The different kinetic behavior can be correlated with different conformational changes observed under the interaction with ALP. Fluorescence experiments showed a raising of the binding constant with temperature. FTIR determinations showed that the complex with bathophenanthroline modifies the ALP structure but maintains the helical structure. The other copper complexes provoked a structural unfolding, decreasing the α-helix content. None of them affect the dephosphorylation enzyme ability. Even though the interactions and structural modifications on ALP are different, it is evident that the presence of copper favors enzymatic activity. The observed electrostatic interactions probably benefit the dissociation of the bound phosphate. The results suggest potential biological applications for the studied compounds.

Potentiometric Studies on Binary and Ternary Complexes of Ni(II) and Cu(II) Ions with L-Valine and Paracetamol

The protonation constants of the free ligands and the stability constants of binary and ternary complexes of bivalent metal ions of Ni(II) and Cu(II) with a biologically important amino acid of L-valine, Val, and paracetamol, Para, were studied potentiometrically in aqueous solutions at 313.15 ± 0.1 K and a fixed ionic strength of I = 0.10 M NaCl. The complexation model for each system was established using the Irving-Rossotti equation. The formation of the 1:2 or 1:1 binary complexes and 1:1:1 ternary complexes in which the amino acid Val was used as the primary ligand and Para as the secondary ligand, as inferred from the corresponding potentiometric pH-metric titration curves, and their relative stabilities compared to the corresponding ML and ML2 binary complexes are expressed in terms of statistical parameters ∆logK, logK1 and logK2. The complex stability was found to follow the order of Cu(II) > Ni(II). Through these diagnostic studies, it was possible to give the general formula of compounds prepared from amino acids and paracetamol. Amino acid binds to the central ion through oxygen in the hydroxyl group and nitrogen atom in the amine group (-NH2), whereas paracetamol forms a unipolar bond by binding to the concentrated ion through the oxygen atom in the hydroxyl group. Most of the nickel complexes had octahedral symmetry with valine and paracetamol ligands, while the copper complexes had square or hierarchical to square base symmetry.

Multi-Scale Structural Insights into Enzymatically Hydrolyzed Lentil Starch Concentrates Prepared by In Vitro Method Using Different Types of Enzymes.

This study was undertaken to investigate the enzymatic hydrolysis of lentil starch concentrates from conventional cooked seeds (CCLSC) by the action of different types of enzymes, including pancreatin (PC-EHSC), heat-stable α-amylase (HS-EHSC), β-amylase (βA-EHSC), amyloglucosidase (AMG-EHSC), and multi-enzymes (βA-HS-AMG-EHSC); their multi-scale structural characteristics of the enzymatic hydrolysis products of lentil starch concentrates were compared. The morphological features distinguished among different samples. The Fourier-transform infrared spectroscopy and solid-state 13C CP/MAS NMR spectral features indicated the possible formation of a binary and ternary complex among amylose, protein and lipids. The X-ray diffraction results revealed that the V-type characteristic diffraction peaks were more obvious for samples including PC-EHSC and βA-EHSC, which was in line with their lowest polydispersity index (DPn). PC-EHSC and βA-EHSC also showed an increased peak intensity of the scattering maximum on the small-angle X-ray scattering spectra, whereas CCLSC exhibited an overall lower peak intensity within the studied q range of scattering. The highest XRD crystallinity and the lowest DPn value obtained for PC-EHSC indicated that the starch polymers modified by pancreatin could produce glucan chains with a comparatively homogenous Mw distribution that are readily recrystallized by hydrogen bonding through chain aggregation. Comparatively, the lowest relative crystallinity for HS-EHSC obtained from XRD suggested that thermostable α-amylolysis was unfavorable for the formation of starch structure with a higher degree of molecular order. This study could provide useful information for the needed research to obtain a deeper understanding of the impact of different amylolysis actions on the structural organization of starch hydrolysates and to provide a theoretical foundation for the development of fermentable enzymatically hydrolyzed starch with well-tailored physiological properties.

Storage stability and multi-spectroscopy analysis of the ternary complex induced by mulberry anthocyanin extract interacting with whey protein isolate and rutin under acidic conditions

In the present study, we have investigated the relevant mechanisms underlying the stabilizing effects of whey protein isolate (WPI) and rutin (Ru) on the mulberry anthocyanin extract (MAE) solution at pH 3.6 during storage. The results demonstrated that there was no pronounced difference in color between the MAE solutions when adding WPI and Ru separately and together. However, the combined use of WPI and Ru reduced the total anthocyanin degradation rate by 16.2% and 18.3% compared to WPI and Ru used individually, respectively, after 9 days of storage at 40 °C. Fluorescence, UV–visible, Fourier transform infrared, and circular dichroism spectroscopies, as well as particle size and sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis, indicated that the formation of binary and ternary complexes involving β-lactoglobulin (β-LG), cyanidin-3-O-glucoside (C3G), and Ru. The primary interaction between β-LG and C3G was electrostatic interaction, with an enthalpy change (ΔH) of −25.02 kJ mol−1 and an entropy change (ΔS) of 7.89 J mol−1 K−1 at 298 K, whereas the interactions between β-LG and Ru involved hydrogen bonding and van der Waals force, with ΔH of −124.80 kJ mol−1 and ΔS of −291.72 J mol−1 K−1 at 298 K. Furthermore, a looser, more open, and disordered structure and larger particle size were observed in protein after the addition of C3G/Ru. The presence of Ru in the ternary complex favored the development of these characteristics. Overall, to protect anthocyanins, β-LG and Ru could exert complexation and copigmentation effects on C3G, respectively. The findings of this study provide a foundation for employing ternary complexes to increase the storage stability of anthocyanins.

Synthesis, characterization, and biological evaluation of Ni, Co, and Cu Metal Complexes with Heterocyclic Compounds

Two new clinically active Schiff bases and their transition metal complexes were synthesized and studied by different spectroscopic and physicochemical methods like NMR, IR, UV-Visible, ESR, TGA, XRD, mass, elemental analysis, molar conductivity and magnetic character. Synthesized complexes and Schiff bases were assessed for invitro antituberculosis activity for Mycobacterium tuberculosis (ATCC–27294) and for antimicrobial activity against drug resistant ESBL (Extended Spectrum β-lactamase) and MBL (Metallo β-lactamase) producing microbial strains. The biological activity of Schiff base was found to improve in presence of transition metal ions. Among the studied metal complexes, copper complexes displayed superior biological activity against all of the microbial strains. Binary complexes of Cu(II), Ni(II), and Co (II) ions have been synthesized by reacting metal salts with a Schiff base, 2-((E)-(5-methylisoxazol-3-ylimino)methyl)-4-methoxyphenol (MIIMMP) in an alcoholic medium. All the metal complexes and schiff base have been characterized by using elemental analysis, IR, UV-VIS, 1H-NMR, 13C-NMR, Mass, ESR spectral data, magnetic moments, TG, and DTA studies. Based on the analytical, spectral data and molecular modeling studies, Ni (II) and Co (II) metal complexes have octahedral geometry, whereas Cu(II) complex has tetragonal geometry. The antimicrobial and cytotoxic activities of the Schiff base and its metal complexes were studied on bacteria, fungi, and human cervical carcinoma cells (HeLa).

Binary complexes of whey protein fibers/isolates and fish gelatins for emulsion stabilization

In this work, fish gelatins (FG) were mixed with whey protein fibers (WPF) and native whey protein isolates (WPI) under acidic and neutral pH conditions, respectively. The objective of this study was to explore how binary protein FG and WPI/WPF cooperated to stabilize oil-in-water emulsion systems. The emulsion, stabilized solely by WPI, flocculated and coalesced easily at both pH values. Fibrillation could increase surface hydrophobicity and interfacial activity at pH 7, resulting in improved creaming stability of emulsions compared to natural WPI. However, the improvement in creaming stability was limited. When FG cooperated with WPI and WPF, FG could contribute to the formation of a 3D network to enhance the physical stability of emulsions. In addition, WPI and WPF could contribute to surface activity in binary proteins. FG-WPF exhibited better compatibility than FG-WPI and a faster gelation rate, superior viscoelastic properties, and greater deformation resistance. In addition, WPF may help to improve the gelation behavior of FG-WPF at pH 3. This research introduced a new binary protein system consisting of whey protein fibers and fish gelatins that might be used as promising emulsifiers and stabilizers in emulsion systems.

General Metadynamics Protocol To Simulate Activation/Deactivation of Class A GPCRs: Proof of Principle for the Serotonin Receptor.

We present a generally applicable metadynamics protocol for characterizing the activation free-energy profiles of class A G-protein coupled receptors and a proof-of-principle study for the 5HT1A-receptor. The almost universal A100 activation index, which depends on five inter-helix distances, is used as the single collective variable in well-tempered multiple-walker metadynamics simulations. Here, we show free-energy profiles for the serotonin receptor as binary (apo-receptor + G-protein-α-subunit and receptor + ligand) and ternary complexes with two prototypical orthosteric ligands: the full agonist serotonin and the partial agonist aripiprazole. Our results are not only compatible with previously reported experimental and computational data, but they also allow differences between active and inactive conformations to be determined in unprecedented atomic detail, and with respect to the so-called microswitches that have been suggested as determinants of activation, giving insight into their role in the activation mechanism.

Rapid and versatile colorimetric sensor based on luminescent bacterium for water comprehensive toxicity detection

In this study, a high-efficiency colorimetric sensor for water toxicity assessment was successfully constructed by the visual analysis with naked eyes and the high-throughput measurement with a microplate reader. The bioluminescent Photobacterium phoshoreum T3 spp. (T3) and Prussian blue (PB) were used as model bacterium and indicator of the colorimetric sensor, respectively. In order to accurately detect acute toxicities of wastewater, the experimental conditions, concentrations of cells, K3[Fe(CN)6] and NaCl, reaction temperature and time, were optimized to be OD600 = 2, 8 mM, 1.2%, 26.5 °C and 25 min, respectively. Then several samples of simulated wastewater containing Hg2+, Cd2+, Zn2+, 3,5-dichlorophenol (DCP) and formaldehyde (HCHO) were tested. The composite biotoxicity of dry battery leachate and real water sample was also evaluated. The IC50 values of Hg2+, Cd2+, Zn2+ and DCP obtained were 3.60, 1.56, 0.96 and 11.77 mg L−1, respectively. Moreover, a toxic unit (TU) model was applied to evaluate the binary complex toxicity of Hg2+ + Cd2+, Hg2+ + Zn2+ and DCP + Zn2+, which showed antagonistic effects. The work demonstrates that the promising high-efficiency sensor can detect quickly and sensitively the single and joint toxicities of multi-pollutants in water, which possesses extensive potentials in field of toxicity detection.

Enhanced Solubility and Stability of Aripiprazole in Binary and Ternary Inclusion Complexes Using Hydroxy Propyl Beta Cyclodextrin (HPβCD) and L-Arginine.

The low water solubility of an active pharmaceutical ingredient (aripiprazole) is one of the most critical challenges in pharmaceutical research and development. This antipsychotic drug has an inadequate therapeutic impact because of its minimal and idiosyncratic oral bioavailability to treat schizophrenia. The main objective of this study was to improve the solubility and stability of the antipsychotic drug aripiprazole (ARP) via forming binary as well as ternary inclusion complexes with hydroxypropyl-β-cyclodextrin (HPβCD) and L-Arginine (LA) as solubility enhancers. Physical mixing and lyophilization were used in different molar ratios. The developed formulations were analyzed by saturation solubility analysis, and dissolution studies were performed using the pedal method. The formulations were characterized by FTIR, XRD, DSC, SEM, and TGA. The results showcased that the addition of HPβCD and LA inclusion complexes enhanced the stability, in contrast to the binary formulations and ternary formulations prepared by physical mixing and solvent evaporation. Ternary formulation HLY47 improved dissolution rates by six times in simulated gastric fluid (SGF). However, the effect of LA on the solubility enhancement was concentration-dependent and showed optimal enhancement at the ratio of 1:1:0.27. FTIR spectra showed the bond shifting, which confirmed the formation of new complexes. The surface morphology of complexes in SEM studies showed the rough surface of lyophilization and solvent evaporation products, while physical mixing revealed a comparatively crystalline surface. The exothermic peaks in DSC diffractograms showed diminished peaks previously observed in the diffractogram of pure drug and LA. Lyophilized ternary complexes displayed significantly enhanced thermal stability, as observed from the thermograms of TGA. In conclusion, it was observed that the preparation method and a specific drug-to-polymer and amino acid ratio are critical for achieving high drug solubility and stability. These complexes seem to be promising candidates for novel drug delivery systems development.

Effect of Halogen at the Divalent Sulfur Atom on the Properties of Complexes with a Chalcogen and Hydrogen Bond

Binary complexes with a chalcogen (A complexes) and hydrogen (B complexes) bond formed by SHX molecules (X = F, Cl, Br, OH) of divalent sulfur and a water molecule have been calculated by the MP2/aug-cc-pVTZ quantum chemical method. An NBO analysis was performed for complexes of both types along with the topological analysis of electron density and decomposition of the binding energy into components. The quantum chemical calculations showed that the binding energies, interorbital interaction energies of monomers, and electron densities at the critical point (3, –1) of intermolecular contact are close in the A and B complexes. The main contribution to stabilization of the complexes is made by the electrostatic interaction; in the B complexes, however, the contribution of the charge transfer component is also significant. The dispersion energy plays a significant role in the binding of monomers in complexes of both types. According to the calculations, the interconversion of A and B complexes occurs with a very low activation barrier.

Design and Characterization of Bivalent Molecules Against SARS-CoV2

Abstract The pandemic of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has compelled extraordinary attention to the development of therapeutic reagents. The favorable physical properties of nanobodies make them attractive candidates for investigations of their ability to block viral entry. By X-ray crystallography we determined the structural basis of the interaction of a panel of synthetic nanobodies (Sb14, Sb16, Sb45 and Sb68) with the SARS-CoV-2 receptor binding domain (RBD): binary complexes of Sb16–RBD and Sb45–RBD; a ternary complex of Sb14–RBD–Sb68, and Sb45–RBD–Sb68. Sb16 and Sb45 bind the RBD with identical footprints with ACE2, but their complementarity determining regions (CDR)2 and CDR3 are oriented diametrically oppositely. The ternary structure of the Sb45-RBD-Sb68 complex indicates that Sb45 binds squarely at the ACE2 interface, whereas Sb68 attaches toward the ACE2 interface's perimeter. The ternary configuration suggests that several sybodies may capture a sizable portion of the RBD's surface. These sybody structures provided structural insights that were used to create novel, highly potent biparatopic nanobodies and bivalent molecules with ACE2 and ACE2 binding scaffold mimicking miniproteins that bind the RBD with high affinity and neutralize SARS-CoV-2 and variants. Supported by the Intramural research program of the NIAID/NIH

Soy protein isolate-citrus pectin-gallic acid ternary composite high internal phase Pickering emulsion for delivery of β-carotene: Physicochemical, structural and digestive properties

The structure properties, stability and β-carotene slow-release mechanism of soybean protein isolate-citrus pectin-gallic acid complex (SPI-CP-GA) stabilized high-internal phase Pickering emulsion (HIPPE) were investigated. The results showed that compared with the SPI-CP binary complex, the turbidity of the SPI-CP-GA ternary complex increased from 2.174 ± 0.001 to 3.027 ± 0.001, the surface wettability was increased, the infrared peaks was blue-shifted, changed from hydrophilic to hydrophobic, and the equilibrium interfacial tension of particles increased from 10.77 ± 0.02 mN/m to 13.46 ± 0.03 mN/m, the complex was more stable. When the GA was 2.0 mg/mL, the encapsulation efficiency of β-carotene was higher. With increased GA concentration and oil phase volume fraction (φ), the apparent viscosity and viscoelastic behavior of HIPPE performed well, forming a stable gel network structure. After 30 days of storage, there was no oil separation in the sample group with GA concentration of 2.0 mg/mL and φ = 0.7, and the stability was strong. After gastrointestinal digestion, the particle size of the HIPPE decreased from 13.51 ± 0.86 μm to 7.70 ± 0.68 μm, the free fatty acid (FFA) release rate was 22.03%, and the bioaccessibility of β-carotene was 6.67 ± 0.19%, and the sustained-release effect was obvious. These results indicated that the SPI-CP-GA ternary complex is a potential stabilizer for HIPPE, and providing theoretical guidance for the design of protein-polysaccharide-polyphenol stabilized HIPPE.