Noncovalent Complexes Research Articles

Nanoelectrospray based synthesis of large, transportable membranes with integrated membrane proteins

Membrane proteins tend to be difficult to study since they need to be integrated into a lipid bilayer membrane to function properly. This study presents a method to synthesize a macroscopically large and freely transportable membrane with integrated membrane proteins which is useful for studying membrane proteins and protein complexes in isolation. The method could serve as a blueprint for the production of larger quantities of functionalised membranes for integration into technical devices similar to the MinION DNA sequencer. It is possible to self-assemble larger biological membranes on solid surfaces. However, they cannot be removed from their solid support without destroying them. In transportable form, self-assembled membranes are limited to sizes of about 17 nm in nanodiscs. Here we electrospray a series of molecular layers onto the liquid surface of a buffer solution which creates a flat, liquid environment on the surface that directs the self-assembly of the membrane. This method enables us to experimentally control the membrane composition and to succeed in producing large membranes with integrated OmpG, a transmembrane pore protein. The technique is compatible with the assembly of membrane based protein complexes. Listeriolysin O and pneumolysin efficiently assemble into non-covalent membrane pore complexes of approximately 30 units or more within the surface layer.

7222 Structural and Mechanistic Studies of the Bioactive Anti-Müllerian Hormone Procomplex

Abstract Disclosure: J.A. Howard: None. L. Hok: None. N.J. Sanford: None. R.L. Cate: None. K. Hart: Employee; Self; Regeneron Pharmaceuticals. E. Leach: None. D. Pepin: None. P.K. Donahoe: None. T.B. Thompson: Advisory Board Member; Self; Oviva Therapeutics, Keros Therapeutics. The Anti-Mullerian hormone (AMH), a divergent member of the TGF-beta signaling superfamily, plays crucial roles in reproductive development and maintenance. Owing to its key role as a negative feedback regulator in folliculogenesis, AMH has garnered significant interest for therapeutic applications in contraception and oncofertility. The bioactive form of AMH is a noncovalent complex, comprising the TGFβ-like signaling domain and a dimeric prodomain whose structure remains largely unexplored. The prodomain component is necessary for the dimerization and secretion of the signaling domain, shuttling the ligand to autocrine, paracrine, and endocrine targets. In contrast, the structure and biochemistry of this domain remain poorly characterized, and its role in enhancing AMH signaling remains unclear. This gap in understanding significantly limits the enhancement and wider application of AMH-based protein therapeutics. Molecular modeling unveiled an unexpected AMH prodomain structure: an N-terminal dimerizing domain (NTD) linked to a novel C-terminal binding domain (CTD). This atypical design was affirmed by both small-angle X-ray scattering and negative-stain EM. The CTD introduces a unique TGFβ superfamily fold consisting of a four-helix bundle and an unstructured binding “belt”. The more prodomain-like NTD does not interact with the signaling ligand, nor does it consistently interact with the CTD. Both domains exhibit high levels of interspecies conservation as well as disease-causing mutations, such as those found in PMDS, PCOS, and POI. Using single-particle Cryo-EM we have elucidated the molecular mechanisms of the interaction between the AMH prodomain and signaling domain bound by mAb 6E11. Our 3.2Å cryo-EM structure confirmed the predicted architecture and binding function of the CTD and demonstrated a new dimension of conformational plasticity within the signaling ligand. We observed movements up to 5Å at the fingertips and 10Å in the outer helices of the CTD. More unexpectedly, the conformation of the AMH signaling ligand in the procomplex form is far more open and extended than has been observed in any other structure of a TGF-beta superfamily ligand, including the AMH ligand bound to its receptor AMHR2. We see that transitioning from a prodomain-bound to a receptor-bound state involves significant conformational remodeling of the signaling domain. This reorganization supports a conformational shift mechanism for AMH signaling in which bivalent binding of AMHR2 at the cell surface induces a >15Å and 38° closing of the ligand fingertips, leading to prodomain displacement and subsequent recruitment of type I receptors. Our findings correct earlier structural misconceptions and build a comprehensive model for interpreting existing functional data. This structure provides a foundation for understanding AMH dysregulation and developing advanced AMH therapeutics. Presentation: 6/1/2024

Biofunctionalized dissolvable hydrogel microbeads enable efficient characterization of native protein complexes

The characterization of protein complex is vital for unraveling biological mechanisms in various life processes. Despite advancements in biophysical tools, the capture of non-covalent complexes and deciphering of their biochemical composition continue to present challenges for low-input samples. Here we introduce SNAP-MS, a Stationary-phase-dissolvable Native Affinity Purification and Mass Spectrometric characterization strategy. It allows for highly efficient purification and characterization from inputs at the pico-mole level. SNAP-MS replaces traditional elution with matrix dissolving during the recovery of captured targets, enabling the use of high-affinity bait-target pairs and eliminates interstitial voids. The purified intact protein complexes are compatible with native MS, which provides structural information including stoichiometry, topology, and distribution of proteoforms, size variants and interaction states. An algorithm utilizes the bait as a charge remover and mass corrector significantly enhances the accuracy of analyzing heterogeneously glycosylated complexes. With a sample-to-data time as brief as 2 hours, SNAP-MS demonstrates considerable versatility in characterizing native complexes from biological samples, including blood samples.

Theoretical Insight into Complexation Between Cyclocarbons and C60 Fullerene.

This work conducts a comprehensive theoretical study on the non-covalent complexation between cyclocarbons and C60 fullerene for the first time. The binding energy between cyclocarbons and C60 fullerene is significantly stronger than that between two C18 or two C60 fullerenes, indicating a particularly strong affinity. The cyclocarbons and C60 fullerene can spontaneously assemble into complexes in the gas phase at room temperature, and the hydrophobic effect caused by the solvent environment can promote this binding. The binding strength with C60 fullerene increases almost linearly with the increase of cyclocarbon size, and the C34@C60 dimer exhibits a perfect nano-Saturn structure. As the ring size increases, the angle between the two cyclocarbons of the 2 : 1 trimers formed by cyclocarbons and C60 fullerene gradually decreases. In C60@2 C34 trimer, the fullerene is symmetrically surrounded by two cyclocarbons. The results on the trimers formed by cyclocarbon and C60 fullerenes in a 1 : 2 ratio showed when the cyclocarbon sandwiched between two fullerenes is not quite large, the trimers exhibit an ideal dumbbell-like structure, and the presence of the first fullerene has a significant synergistic effect on the binding of the second one. The cyclocarbon greatly promotes the dimerization of fullerenes, which acted as a "molecular glue".

Photoinduced Nonadiabatic Dynamics of a Single-Walled Carbon Nanotube-Porphyrin Complex.

Single-walled carbon nanotubes (SWCNTs) have gained a lot of attention in the past few decades due to their promising optoelectronic properties. In addition, SWCNTs can form complexes that have good chemical stability and transport properties with other optical functional materials through noncovalent interactions. Elucidating the detailed mechanism of these complexes is of great significance for improving their optoelectronic properties. Nevertheless, simulating the photoinduced dynamics of these complexes accurately is rather challenging since they usually contain hundreds of atoms. To save computational efforts, most of the previous works have ignored the excitonic effects by employing nonadiabatic carrier (electron and hole) dynamics simulations. To properly consider the influence of excitonic effects on the photoinduced ultrafast processes of the SWCNT-tetraphenyl porphyrin (H2TPP) complex and to further improve the computational efficiency, we developed the nonadiabatic molecular dynamics (NAMD) method based on the extended tight binding-based simplified Tamm-Dancoff approximation (sTDA-xTB), which is applied to study the ultrafast photoinduced dynamics of the noncovalent SWCNT-porphyrin complex. In combination with statically electronic structure calculations, the present work successfully reveals the detailed microscopic mechanism of the ultrafast excitation energy transfer process of the complex. Upon local excitation on the H2TPP molecule, an ultrafast energy transfer process occurs from H2TPP (SWCNT-H2TPP*) to SWCNT (SWCNT*-H2TPP) within 10 fs. Then, two slower processes corresponding to the energy transfer from H2TPP to SWCNT and hole transfer from H2TPP to SWCNT take place in the 1 ps time scale. The sTDA-xTB-based electronic structure calculation and NAMD simulation results not only match the previous experimental observations from static and transient spectra but also provide more insights into the detailed information on the complex's photoinduced dynamics. Therefore, the sTDA-xTB-based NAMD method is a powerful theoretical tool for studying the ultrafast photoinduced dynamics in large extended systems with a large number of electronically excited states, which could be helpful for the subsequent design of SWCNT-based functional materials.

Concurrent processes in the time-resolved solvation and Coulomb ejection of sodium ions in helium nanodroplets

Recent pump-probe experiments [Albrechtsen et al., Nature 623, 319 (2023)] have explored the gradual solvation of sodium cations in contact with helium nanodroplets, using a fully solvated xenon atom as a probe exerting a repulsive interaction after its own ionization. In this communication, we computationally examine by means of atomistic ring-polymer molecular dynamics the mechanisms of successive ionizations, shell formation, and Coulomb ejection that all take place within tens of picoseconds and show that their interplay subtly depends on the time delay between the two ionizations but also on the droplet size. The possibility of forming solvated Na+Xe non-covalent complexes under a few tens of picoseconds in such experiments is ruled out based on fragment distributions.

Preparation and characterization of lactoferrin-polyphenol conjugate with stabilizing effects on fish oil high internal phase Pickering emulsions

The combination of protein and polyphenol is an effective approach to improve the stability of protein emulsions. The lactoferrin (LF)-(−)-epigallocatechin-3-gallate (EGCG) covalent complex (LF-EGCG) was first prepared by alkali-induced reaction, then the structure and physicochemical properties between LF-EGCG and non-covalent complex (LF + EGCG) were compared, and finally the stability of complexes to fish oil high internal Pickering emulsions (HIPPEs) was tested. Results showed that LF-EGCG had stronger antioxidant activity, higher thermal stability, and better surface wettability than LF + EGCG. Meanwhile, the complexes showed no cytotoxicity within the tested concentration range (12.5–200 μg/mL). The HIPPEs stabilized with LF-EGCG possessed smaller droplet size, higher ζ-potential, and more uniform oil/water proton distribution. Covalent treatment also enhanced the storage, thermal, freeze-thaw and physical stability of LF HIPPEs. Furthermore, due to the higher antioxidant activity and denser microstructure, LF-EGCG HIPPE can more effectively inhibit the oxidation of fish oil.

Fluorogenic in-situ Labelling of Gelatin Polymer in Aqueous Solution and Hydrogel.

Gelatin polymers made from partially degraded collagen are important biomaterials, but their in-situ analysis suffers from uncontrollable covalent labelling and poor spatial-temporal imaging resolution. Herein, three tetrazolate-tagged tetraphenylethylene fluorophores (TPE-TAs) are introduced for practical fluorogenic labelling of gelatin in aqueous phase and hydrogels. These probes with aggregation-induced emission characteristics offer negligible background and elicit turn-on fluorescence by simply mixing with the gelatin in aqueous phase, giving a detection limit of 0.15 mg/L over a linear dynamic range up to 100 mg/L. This method does not work for collagens and causes minimal interference with gelatin properties. Mechanistic studies reveal a key role for multivalent electrostatic interactions between the abundant basic residues in gelatin (e. g., lysine, hydroxylysine, arginine) and anionic tetrazolate moieties of the lipophilic fluorophore synergistically in spatially rigid macromolecular encapsulation to achieve fluorogenic labelling. The AIE strategy by forming non-covalent fluorophore-gelatin complexes was developed for novel hydrogels that exhibited reversible fluorescence in response to dynamic microstructural changes in the hydrogel scaffold upon salting-in/out treatments, and enabled high spatial-temporal imaging of the fiber network in lyophilized samples. This work may open up avenues for in-situ imaging analysis and evaluation of gelatin-based biomaterials during processes such as in vivo degradation and mineralization.

Abstract PR-01: Systemic targeting of therapeutic RNA to pancreatic ductal adenocarcinoma via a novel, cell-penetrating, and nucleic acid-binding monoclonal antibody

Abstract There is intense interest in developing nucleic acid ligands for immune stimulation of the tumor microenvironment via pattern recognition receptors (PRRs), particularly for treating “cold” tumors like pancreatic ductal adenocarcinoma (PDAC). However, selective delivery of intact and functional RNAs after intravenous administration in a tumor-specific manner to avoid systemic toxicity has been challenging. Many current efforts rely on the direct intra-tumoral injection of RNAs or other stimulatory immune ligands, which is therapeutically sub-optimal, especially for pancreatic tumors and metastases. Here, we present a groundbreaking and unique cancer treatment approach using a lupus-derived, cell-penetrating antibody to deliver nucleic acids to PDAC tumors in vivo. This antibody, a modified version of the initially reported 3E10-D31N, designated TMAB3, forms non-covalent complexes with RNAs. We tested our delivery platform in genetically engineered mouse models (Pdx-1 Cre KrasG12D) and flank and orthoptic allographs of pancreatic cancer (Pdx-1 Cre KrasG12D, p53R172H/- KPC cells) in immunocompetent models. Using 3p-hpRNA, an agonist of the pattern recognition receptor retinoic acid-inducible gene-I (RIG-I), we observed robust anti-tumor efficacy of systemically administered TMAB3/3p-hpRNA complexes in an orthotopic pancreatic cancer model. Treatment tripled animal survival and decreased tumor growth, specifically targeting the malignant cells, with a 1500-fold difference in RNA delivery into tumor cells versus non-malignant cells within the tumor mass. While an immunosuppressive microenvironment typically characterizes PDAC, we found that RIG-I stimulation via TMAB3/3p-hpRNA treatment elicited a potent anti-tumoral immune response characterized by induction of apoptosis in tumor cells and infiltration of CD8+ T cells using single-cell RNASeq and confirming using FACS and immunocompromised mice. In vitro and in vivo studies demonstrated that cancer-cell delivery was mediated by nucleoside transporter ENT2, which is highly expressed in PDAC compared to healthy and benign tissues. These results were recapitulated in orthogonal models of immunologically cold tumors, including melanoma and medulloblastoma. Together, these studies demonstrate that the TMAB3 antibody can 1) precisely localize and enter pancreatic tumor cells, 2) promote CD8+ T cell infiltrates, and 3) rapidly deliver RNA payloads specifically to tumors. Given the known stromal barrier in pancreatic ductal adenocarcinoma, TMAB3 provides a novel targeted delivery platform for a broad range of therapeutics for these difficult-to-treat tumors. Citation Format: Diana Martinez-Saucedo, Elias Quijano, Zaira Ianniello, Madison Rackear, Yanfeng Liu, Denise Hegan, Haoting Chen, Xinning Shan, Robert Tseng, Deanne Yugawa, Natasha Pinto-Medici, Sumedha Chowdhury, Ranjit S Bindra, Marie E Robert, W. Mark Saltzman, Luisa F Escobar-Hoyos, Peter M Glazer. Systemic targeting of therapeutic RNA to pancreatic ductal adenocarcinoma via a novel, cell-penetrating, and nucleic acid-binding monoclonal antibody [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Pancreatic Cancer Research; 2024 Sep 15-18; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(17 Suppl_2):Abstract nr PR-01.

Effects of Protein on Green Tea Quality in a Milk-Tea Model during Heat Treatment: Antioxidant Activity, Foaming Properties, and Unbound Small-molecule Metabolome

Tea drinks/beverage has a long history and milk is often added to enhance its taste and nutritional value, whereas the interaction between the tea bioactive compounds with proteins has not been systematically investigated. In this study, a milk-tea model was prepared by mixing green tea solution with milk and then heated at 100°C for 15 min. The milk tea was then measured using biochemical assay, antioxidant detection kit, microscopy as well as HPLC-QTOF-MS/MS after ultrafiltration. The study found that as the concentration of milk protein increased in the milk-tea system, the total phenol-protein binding rate raised from 19.63% to 51.08%, which led to a decrease in free polyphenol content. This decrease of polyphenol was also revealed in the antioxidant capacity, including 2,2-diphenyl-1-picrylhydrazyl radical scavenging ability and ferric ion reducing antioxidant power, in a dose-dependent manner. Untargeted metabolomics results revealed that the majority of small-molecule compounds/polyphenols in tea, such as epigallocatechin gallate, (-)-epicatechin gallate, and Catechin 5,7,-di-O-gallate, bound to milk proteins and were removed by ultrafiltration after addition of milk and heat treatment. The SDS-PAGE and Native-PAGE results further indicated that small molecule compounds in tea formed covalent and non-covalent complexes by binding to milk proteins. All above results partially explained that milk proteins form conjugates with tea small-molecule compounds. Consistently, the particle size of the tea-milk system increased as the tea concentration increased, but the polymer dispersity index decreased, indicating a more uniform molecular weight distribution of the particles in the system. Addition of milk protein enhanced foam ability in the milk-tea system but reduced foam stability. In summary, our findings suggest that the proportion of milk added to tea infusion needs to be considered to maintain the quality of milk-tea from multiple perspectives, including stability, nutritional quality and antioxidant activity.

Dietary polyphenols reduced the allergenicity of β-lactoglobulin via non-covalent interactions: a study on the structure-allergenicity relationship

Studies showed that complexation of polyphenols with milk allergens reduced their immunogenic potential. However, the relationship between structures of polyphenols and their hypoallergenic effects on milk allergens in association with physiological and conformational changes of the complexes remain unclear. In this study, polyphenols from eight botanical sources were extracted to prepare non-covalent complexes with β-lactoglobulin (β-LG), a major allergen in milk. The dominant phenolic compounds bound to β-LG with a diminished allergenicity were identified to investigate their respective role on the structural and allergenic properties of β-LG. Extracts from Vaccinium fruits and black soybeans were found to have great inhibitory effects on the IgE- and IgG-binding abilities of β-LG. Among the fourteen structure-related phenolic compounds, flavonoids and tannins with larger MWs and multi-hydroxyl substituents, notably rutin, EGCG, and ellagitannins were more potent to elicit changes on the conformational structures of β-LG to decrease the allergenicity of complexed β-LG. Correlation analysis further demonstrated that a destabilized secondary structure and protein depolymerization caused by polyphenol-binding were closely related to the allergenicity property of formed complexes. This study provides insights into the understanding of structure-allergenicity relationship of β-LG-polyphenol interactions and would benefit the development of polyphenol-fortified matrices with hypoallergenic potential.

Effects of a xylitol-casein complex on insulin resistance and gut microbiota composition in high-fat-diet + streptozotocin-induced type 2 diabetes mellitus mice

This study investigated the effects of a xylitol-casein non-covalent complex (XC) on parameters related to type 2 diabetes mellitus (T2DM), in addition to related changes in gut microbiome composition and functions. High-fat-diet (HFD) + streptozotocin (STZ)-induced T2DM mice were treated with xylitol (XY), casein (CN), and XC, after which fecal samples were collected for gut microbiota composition and diversity analyses based on 16S rRNA high-throughput sequencing and multivariate statistics. XC decreased body weight and improved glucose tolerance, insulin sensitivity, pancreas impairment, blood lipid levels, and liver function in T2DM mice compared to XY- and CN-treated mice. Furthermore, XC modulated the α-diversity, β-diversity and gut microbiota composition. Based on Spearman’s correlation analysis, the relative abundances of Alistipes, Bacteroides, and Faecalibaculum were positively correlated and those of Akkermansia, Lactobacillus, Bifidobacterium, and Turicibacter were negatively correlated with the phenotypes related to the improvement of T2DM. In conclusion, we found that XC alleviated insulin resistance by restoring the gut microbiota of T2DM mice. Our results provide strong evidence for the beneficial effects of XC on T2DM and motivation for further investigation in animal models and, eventually, human trials.

Noncovalent interaction between proanthocyanidins and soy protein isolate fibers: structure, functionality and interaction mechanism

This study focused on the addition of different concentrations of proanthocyanidins (OPC) to form noncovalent complexes with soy protein isolate fibers (SPIF). To investigate the effects of polyphenols on the structural and functional properties of protein fibers and to elucidate mechanism of their interaction. The addition of OPC unfolded the internal structure of the proteins, exposing the hydrophobic groups and reducing the β-sheet structure of SPIF, forming the SPIF-OPC complexes. And the binding of the two would be close to saturation, at the final concentration of added OPC was 0.5 or 1 mg/mL. Multiple spectroscopy and isothermal titration calorimetry analyses indicated that static quenching was the mechanism of fluorescence quenching of SPIF by OPC. The two spontaneously combined through hydrogen bonding and hydrophobic interactions. Transmission electron microscopy observations of the microscopic morphology also indicated that the addition of OPC altered the original long, semi-flexible fibers structure of SPIF. The fibers gradually showed a large number of branches and became short and curved. When the final concentration of added OPC was 4 mg/mL, the emulsifying activity index of SPIF increased by 78.40% and foaming capacity of SPIF increased by 37.10%. The interaction mechanism of different concentrations of OPC with SPIF will be comprehensively understood from this study, thus expanding its application in food, medicine, cosmetics and other fields.

Polyphenol co-pigments enhanced the antioxidant capacity and color stability of blue honeysuckle juice during storage

The study aimed to assess the impact of incorporating five co-pigments (gallic acid, quercetin, rutin, catechin, and epigallocatechin gallate (EGCG)) on the color stability of blue honeysuckle juice (BHJ). Additionally, it sought to determine the influence of varying proportions of anthocyanins in an accelerated test (light at 40 °C for 24 d). Results indicated that the addition of polyphenol co-pigments effectively mitigated the thermal degradation of anthocyanins, enhancing color saturation and antioxidant capacity of BHJ. Notably, quercetin, rutin, catechin, and EGCG exhibited superior efficacy compared to gallic acid. FTIR analysis revealed non-covalent complex formation between co-pigments and anthocyanins, including hydrogen bonds and van der Waals forces, thereby shielding them from degradation. HPLC-ESI-QTOF-MS2 identified 15 anthocyanins and 39 non-anthocyanin polyphenols. Addition of co-pigments effectively curbed anthocyanin degradation, thus stabilizing juice system. Consequently, judicious incorporation of co-pigments holds promise as a technology for enhancing the color quality and stability of BHJ during processing.

Spectroscopic and solution properties characterization of quaternary ammonium ion containing polycations complexed with fluorescent rhodamine sulfonic acid dyes

Based on the growing range of applications for polycations in research and commercial materials, a continuing need exists to advance the fundamental knowledge and understanding of this class of materials. Spectroscopic and solution properties characterizations of noncovalently labeled, fluorescent Alexa Fluor® dye complexes of two commercial polycations, poly(2-(trimethylamino) ethyl methacrylate) monocation and poly[bis[2-chloroethyl] ether-alt-1,3-bis[3-(dimethylamino) propyl] urea] dication are reported to help address this need. A variety of fluorescence spectroscopic methods are used with a special emphasis on fluorescence correlation spectroscopy (FCS) which is applied to characterize the Stokes radius (RS) and equilibrium dissociation constants (Kd) of dye-polycation complexes at nanomolar dye concentrations. Resulting RS values indicate dye binding to individual polycation chains. Measured Kd values in the sub-micromolar range are consistent with strong dye binding. Increasing solution ionic strength with sodium chloride addition inhibits dye binding and decreases the RS of dye-polycation complexes due to size collapse of polycation chains. The complexes differ in their solution stability to ionic strength changes suggesting that both electrostatic and hydrophobic binding interactions influence dye binding. This study establishes the viability of noncovalent dye-polycation complexation in concert with FCS characterization as a general approach for investigating the properties of quaternary ammonium ion containing polycations in aqueous solution.

Is There an Adduct of Pyridine N-Oxide and Boron Trifluoride in the Gaseous State? Gas Electron Diffraction vs Mass Spectrometry.

A study of saturated vapor over the pyridine N-oxide-boron trifluoride (PyO-BF3) adduct was carried out at T = 448(5) K by a synchronous gas electron diffraction/mass spectrometry (GED/MS) experiment. Due to the absence of ions in the mass spectrum, indicating the presence of a structure with an O-B dative bond, several models of vapor composition were tested by the GED method. It was found that the dominant molecular form (up to 100%) in vapor is the PyO-BF3 adduct. Using the DFT/M06-2X/aug-cc-pVTZ method, geometric optimization of the molecular ion [PyO-BF3]+ was carried out, which showed its intrinsic instability and dissociation into a [PyO]+ cation and a BF3 molecule. This study certainly demonstrates the significant advantage of the GED method to determine the qualitative and quantitative gas-phase composition of dative-bonded adducts and other noncovalent complexes as well, whereas the interpretation of mass spectra may be ambiguous due to the possible intrinsic instability of ions containing a dative bond. The nature of the O-B bond is discussed in terms of the natural bond orbitals (NBOs) and the quantum theory of atoms in molecules (QTAIM). A comparison of structural and energetic parameters for PyO-BF3 and the previously studied BF3 adducts allows the theoretical comprehension of the nature of the O-B bond to be extended and to explain the different thermal stabilities of these compounds.

Iridoid glycosides from noni (Morinda citrifolia L.) fruit pomace: A novel booster strategy for its extraction and will its α-glucosidase inhibitory be increased by acetylation?

Iridoid glycosides (IGs) are secondary metabolites found in plants such as the noni plant (Morinda citrifolia L.), known for their diverse biological activities and potential health benefits. Herein, we screened fifteen natural deep eutectic solvents (NADES) and two conventional solvents (CS, 70% (V/V) methanol and 70% (V/V) ethanol) for extraction of IGs from noni fruit pomace. Our findings indicate that non-acidic NADES promote IG extraction. Glycerol/glycine combined with β-cyclodextrin was selected, and a molecular simulation was performed to elucidate the interaction between NADES components and IGs. Further, the structure-activity relationship and interaction mechanisms of IGs with α-glucosidase were investigated using multispectral and molecular docking tools. The results demonstrated that deacetylation of the B-ring's C-10 improved the inhibitory potential of IGs. Deacetylation produces hydrophobic contacts, which enhance the inhibitory effect of deacetylasperulosidic acid on α-glucosides. Additionally, hydrogen bonds and van der Waals forces drive the formation of non-covalent complexes between IGs and enzymes.

Non-covalent interaction between lactoferrin and theaflavin: Focused on the structural changes, binding mechanism, and functional properties

In this study, non-covalent binding mechanism of lactoferrin (LaF)-theaflavin (TF) complex and its functional properties were investigated. Multi-spectroscopic analyses showed that the secondary structure of LaF was altered with increasing TF concentration. The non-covalent binding of TF to LaF resulted in a reduction in the content of the α-helix and β-sheet, as well as a decrease in the fluorescence intensity of LaF. DSC result showed that non-covalent binding of TF improved thermal stability of LaF. Molecular dynamics simulations confirmed that the stable binding of LaF-TF was driven by hydrogen bonding and hydrophobic interactions. Additionally, non-covalent binding of TF increased the antioxidant capacity and emulsifying properties of LaF. Dynamic interfacial tension indicated that the strong interaction between LaF and TF reduced the interfacial tension, but improved the rheological properties of LaF. The functional characteristics of the non-covalent complex was effectively enhanced, paving the way for its potential use in the food industry.

The Differential Impact of Resorcinarenes on Ferrocene Redox Couple: Towards Electroactive Host-Guest Systems

Alternative to complex labelling of resorcinarene hosts with redox-active probes, non-covalent complex formation offers a unique avenue towards the design of dynamic electro-active host-guest systems towards application in sensors and functional materials. Here, resorcinarene hosts were evaluated with a well-known redox probe, ferrocene (Fc). Specifically, hosts were designed based on tuning the resorcinarene rim with functional groups to allow for hydrogen bonding, pi-pi stacking, hydrophobic and electrostatic interactions. Cyclic voltammetry was used with glassy carbon electrode as a working electrode in organic solvent to evaluate interactions between hosts and Fc. Specifically, the electrochemical properties of Fc, hosts, and host-Fc mixtures were evaluated with respect to the ferrocene/ferrocenium redox couple (reversibility, current and potential). Depending on the host structure, all hosts induced a potential shift of ferrocene/ferrocenium redox couple. The reversibility of the redox couple was maintained with certain hosts, while others resulted in surface fouling. The electrochemical studies were further supplemented by non-electrochemical methods, such as nuclear magnetic resonance, spectroscopy, mass spectrometry as well as theoretical calculations using density functional theory. Data show that controlled and tunable redox host-guest systems with well-defined redox properties may be achieved through chemical modifications of hosts, which may be used to inform functional sensors and devices with a wide range of applications such as phosphate analogue detection.

Tannic acid/non-covalent interaction-mediated modification of hemp seed proteins: Focused on binding mechanisms, oil-water interface behavior, and rheological properties

In this study, hemp seed protein (HSP) was treated to prepare a hemp seed protein-tannic acid non-covalent complex (Nov-HSP). To obtain an emulsifier with excellent properties at the oil-water interface and to propose a potential mechanism of action. The results showed that the α-helix and β-sheet content of Nov-HSP decreased and the intensity of the UV absorption peak increased, respectively, compared with that of HSP. The positions of the maximum fluorescence emission peaks of the synchronized fluorescence spectra were red-shifted to 301.8 nm and 340.6 nm, respectively. Fluorescence quench analysis revealed that static quench occurred between tannins and HSP, with ΔH of −16.138 kJ/mol and ΔS of −0.1073 kJ/mol. The physicochemical and functional properties of HSP and Nov-HSP were analyzed, and it was found that the volume mean diameter of Nov-HSP was 449.28 nm, the absolute value of zeta potential was 20.52 mV, and the solubility was 33.42% at a tannic acid concentration of 1.0 mg/mL. Focusing on the oil-water interfacial properties of Nov-HSP as an emulsifier, it was found that having non-covalent binding effectively increased the diffusion rate of HSP at the interface, thus enhancing the rheological properties of the emulsion. And the emulsification activity index and emulsion stability index were improved to 71.67 m2/g and 32.01 min. These findings provide new perspectives for the phenolic compound-mediated structural remodeling of HSP, expanding its application in emulsion food production.