Binding Reaction Research Articles

CO‐induzierte Dimer‐Dissoziation verursacht Gem‐Dicarbonyl‐Bildung auf einem Einzelatom‐Katalysator‐Modell

AbstractDie Fähigkeit, mehrere Reaktanten an derselben aktiven Stelle zu koordinieren ist eine wichtige Voraussetzung für die breite Anwendbarkeit der Einzelatom‐Katalyse. Modellkatalysatoren sind ideal, um den Zusammenhang zwischen der Geometrie der aktiven Stelle und der Bindung der Reaktanten zu untersuchen, da die Struktur der Einkristalloberflächen genau bestimmt werden kann. Die Adsorbate können mit Hilfe der Rastertunnelmikroskopie (STM) abgebildet werden; dadurch sind direkte Vergleiche mit der Dichtefunktionaltheorie möglich. In dieser Studie verfolgen wir mit Hilfe von STM‐Bildsequenzen einzelne Rh1‐Adatome und Rh2‐Dimere auf Fe3O4(001), während CO bei Raumtemperatur dosiert wird. Die CO‐Adsorption auf Rh1‐Adatomen führt ausschließlich zu stabilen Rh1CO‐Monocarbonylen, bei denen das Rh‐Atom die bevorzugte pseudo‐quadratisch planare Koordination erzielt. In geringem Maß bilden sich auch Rh1(CO)2 Gem‐Dicarbonyl‐Adsorbate; diese entstehen jedoch ausschließlich durch das Aufbrechen von Rh2 Dimeren; der Reaktionsweg führt über ein instabiles Rh2(CO)3 Zwischenprodukt. Unsere Ergebnisse veranschaulichen, wie Minderheitenspezies, die für (über die Probenfläche mittelnde) Spektroskopie‐Methoden unsichtbar sind, eine wichtige Rolle in katalytischen Systemen spielen können, und zeigen, dass die Zersetzung von Dimeren oder kleinen Clustern ein Weg sein kann, um reaktive, metastabile Konfigurationen in der Einzelatom‐Katalyse zu erzeugen.

CO-Induced Dimer Decay Responsible for Gem-Dicarbonyl Formation on a Model Single-Atom Catalyst.

The ability to coordinate multiple reactants at the same active site is important for the wide-spread applicability of single-atom catalysis. Model catalysts are ideal to investigate the link between active site geometry and reactant binding, because the structure of single-crystal surfaces can be precisely determined, the adsorbates imaged by scanning tunneling microscopy (STM), and direct comparisons made to density functional theory. In this study, we follow the evolution of Rh1 adatoms and minority Rh2 dimers on Fe3O4(001) during exposure to CO using time-lapse STM at room temperature. CO adsorption at Rh1 sites results exclusively in stable Rh1CO monocarbonyls, because the Rh atom adapts its coordination to create a stable pseudo-square planar environment. Rh1(CO)2 gem-dicarbonyl species are also observed, but these form exclusively through the breakup of Rh2 dimers via an unstable Rh2(CO)3 intermediate. Overall, our results illustrate how minority species invisible to area-averaging spectra can play an important role in catalytic systems, and show that the decomposition of dimers or small clusters can be an avenue to produce reactive, metastable configurations in single-atom catalysis.

Preparation and Application of Apatite-TiO2 Composite Opacifier: Preventing Titanium Glaze Yellowing through Pre-Combination.

In order to enhance the degree of binding reaction of TiO2 in titanium-containing ceramic glazes and prevent the reaction of its transformation into rutile to eliminate the yellowing phenomenon of the glaze surface, an apatite-TiO2 composite opacifier (ATO) was prepared through the mechanical grinding of hydroxyapatite and anatase TiO2. The properties, opacification mechanism, and yellowing inhibition of the prepared ceramic glazes were studied. The results show that the ATO is characterized by a uniform coating of TiO2 on the surface of the apatite and the formation of close chemical bonding between the apatite and TiO2. The ceramic glaze surface when using an ATO has a white appearance and excellent opacification performance. When an ATO was used, the L*, a*, and b* values of the glaze were 89.99, -0.85, and 3.37, respectively, which were comparable to those of a ZrSiO4 glaze (L*, a*, and b* were 88.24, -0.02, and 2.29, respectively). The opacification of the glaze was slightly lower than that of the TiO2 glaze (L* value was 92.13), but the appearance changed from yellow to the white of the TiO2 glaze (b* value was 9.18). The ceramic glaze layer when using an ATO mainly consists of titanite, glass phase, and a small amount of quartz, and the opacification mechanism is the crystallization of the generated titanite. ATOs can play an active role in solving the critical problem that arises when TiO2 replaces ZrSiO4 as an opacifier.

Integration of virtual screening and proteomics reveals potential targets and pathways for ginsenoside Rg1 against myocardial ischemia

BackgroundGinsenoside Rg1 (Rg1) is one of the main active components in Chinese medicines, Panax ginseng and Panax notoginseng. Research has shown that Rg1 has a protective effect on the cardiovascular system, including anti-myocardial ischemia-reperfusion injury, anti-apoptosis, and promotion of myocardial angiogenesis, suggesting it a potential cardiovascular agent. However, the protective mechanism involved is still not fully understood. MethodsBased on network pharmacology, ligand-based protein docking, proteomics, Western blot, protein recombination and spectroscopic analysis (UV–Vis and fluorescence spectra) techniques, potential targets and pathways for Rg1 against myocardial ischemia (MI) were screened and explored. ResultsAn important target set containing 19 proteins was constructed. Two target proteins with more favorable binding activity for Rg1 against MI were further identified by molecular docking, including mitogen-activated protein kinase 1 (MAPK1) and adenosine kinase (ADK). Meanwhile, Rg1 intervention on H9c2 cells injured by H2O2 showed an inhibitory oxidative phosphorylation (OXPHOS) pathway. The inhibition of Rg1 on MAPK1 and OXPHOS pathway was confirmed by Western blot assay. By protein recombination and spectroscopic analysis, the binding reaction between ADK and Rg1 was also evaluated. ConclusionRg1 can effectively alleviate cardiomyocytes oxidative stress injury via targeting MAPK1 and ADK, and inhibiting oxidative phosphorylation (OXPHOS) pathway. The present study provides scientific basis for the clinical application of the natural active ingredient, Rg1, and also gives rise to a methodological reference to the searching of action targets and pathways of other natural active ingredients.

Co(III), Ni(II), Pd(II) and Pt(II) complexes derived from new benzimidazole-based imine ligands: Preparation, structure, antibacterial, HSA binding and DNA interaction studies

We present here the synthesis of a novel imine base ligand, 2-[(1H-Benzoimidazol-2-ylmethylimino)-methyl]-5-methoxyphenol (HBIM), and its complexes with Co(III), Ni(II), Pd(II), and Pt(II). The ratios of HBIM to metal ions in the synthesis of the metal complexes (TM1-TM4) were 2:1 and 1:1, respectively. Elemental analysis, FT-IR, UV–Visible, NMR, mass spectroscopy, powder XRD, conductance, and magnetic moment measurement were used to clarify the structure of the synthesized ligand and its coordination complexes. Additionally, in vitro antibacterial activity of the compounds was evaluated against a variety of types of bacteria, including B. subtilis, S. aureus, L. monocytogenes, E. coli, V. cholera, and P. aeroginosa. It was shown that metal complexes interacted with human serum albumin (HSA). The findings clearly suggested that the platinum complex (TM4) had a notable interaction with the HSA protein among the produced complexes. Also, it showed that a static quenching process is most likely the mechanism by which complexes quench HSA fluorescence, and that hydrogen binding reactions or van der Waals forces mostly drive entropy in the spontaneous binding contact. Furthermore, the synthesized compounds' binding propensity was assessed using pBR322 DNA cleavage and the calf thymus DNA (CT-DNA) interaction.

Beam theory of cellular microfilaments based on coarse-grained molecular force field

Microfilaments are the main component of the cell cytoskeleton and have a crucial influence on the morphology of living cells. The microfilaments provide mechanical support against applied loads and overcome competing forces that arise from various mechanisms, such as the elasticity of the cell membrane, binding reactions, and surface tension. However, modeling the mechanical properties of microfilaments is an open problem. In the present paper, we proposed a new continuum deformation energy density of microfilaments using the coarse-grained molecular force field and the local differential geometry of curves. In the new theory, the deformation energy density is a function of the microfilament’s strain and the curvature. This theory also unfolded the connections between the mechanical parameters and the coarse-grained force field. We found that the stretching stiffness and the bending stiffness are independent of the section of microfilaments. Microfilaments have a nonlinear stretching-bending term different from the classical beam theory. This means the classical beam theory cannot be directly applied to microfilaments with large deformations. Our theory provides the basis that the modified classical beam theory applies to the nonlinear mechanical behavior of cellular microfilaments.

The adsorption effect on chemical kinetics at the reaction surface in a microfluidic channel of a biosensor for the SARS-Cov-2 detection

The global impact of the Severe Acute Respiratory Syndrome coronavirus has brought about significant changes in the lives of people worldwide, affecting societies and economies. Consequently, there is a growing need to explore the field of research focused on developing wearable sensors capable of continuously monitoring the presence of viruses in the environment. In this particular study, we simulated the binding reaction of the SARS-CoV-2 protein within a microchannel biosensor. One challenge encountered in this setup is the transportation of the analyte to the biosensor's reaction surface. The limited mass transport leads to the creation of a diffusion boundary layer, impeding the overall kinetic reaction. To improve the biosensor performance by enhancing transport, we thoroughly examined the impact of adsorption phenomena on the chemical kinetics. We compared the kinetic response of the biosensor in both cases, i.e. taking into account the adsorption and neglecting it in the numerical model. A parametric study concerning the trapping coefficient was carried out such as the quantity adsorbed at the saturation of a layer, the concentration at half saturation, and the relaxation time. In addition, we investigated the effect of the length of the reaction surface and the inlet velocity of the fluid. The main novelty in this work is to highlight the importance of adsorption on the kinetics of the binding reaction of the SARS-CoV-2-S protein which results in obtaining a complete simulation of the entire process of SARS-Cov-2 binding reaction. Therefore, the adsorption mechanism was described qualitatively and quantitatively using a kinetic model containing a trapping or source term. The obtained results demonstrate the successful integration of adsorption into the kinetic reaction process. The best biosensor performance is achieved in the first case. This theoretical analysis shows that the studied parameters significantly enhance the biosensor performance, especially the sensitivity as well as the response time.

Tuning the Selectivity of Nitrate Reduction via Fine Composition Control of RuPdNP Catalysts.

Herein, aqueous nitrate (NO3 -) reduction is used to explore composition-selectivity relationships of randomly alloyed ruthenium-palladium nanoparticle catalysts to provide insights into the factors affecting selectivity during this and other industrially relevant catalytic reactions. NO3 - reduction proceeds through nitrite (NO2 -) and then nitric oxide (NO), before diverging to form either dinitrogen (N2) or ammonium (NH4 +) as final products, with N2 preferred in potable water treatment but NH4 + preferred for nitrogen recovery. It is shown that the NO3 - and NO starting feedstocks favor NH4 + formation using Ru-rich catalysts, while Pd-rich catalysts favor N2 formation. Conversely, a NO2 - starting feedstock favors NH4 + at ≈50 atomic-% Ru and selectivity decreases with higher Ru content. Mechanistic differences have been probed using density functional theory (DFT). Results show that, for NO3 - and NO feedstocks, the thermodynamics of the competing pathways for N-H and N-N formation lead to preferential NH4 +or N2 production, respectively, while Ru-rich surfaces are susceptible to poisoning by NO2 - feedstock, which displaces H atoms. This leads to a decrease in overall reduction activity and an increase in selectivity toward N2 production. Together, these results demonstrate the importance of tailoring both the reaction pathway thermodynamics and initial reactant binding energies to control overall reaction selectivity.

Biosensor-based serological assay for diagnosing Helicobacter pylori infection

Helicobacter pylori causes the most common bacterial infection involving 50% of the global population. According to the World Health Organization H. pylori infection contributes to approximately 75% of the stomach cancer cases and 5.5% of all types of cancer. Therefore, timely diagnosis of the infection is highly desirable. Serological assays are widely performed for diagnosing H. pylori infection, the most frequently used one being ELISA. In the present study we showed that a serological assay can also be carried out using a biosensor based on Surface Plasmon Resonance (SPR). Unlike our previous studies where we used amplitude detection of the binding reactions, here we applied phase-sensitive detection. It was performed with a the channeled spectroscopic ellipsometer, which allowed fast measurement with high sensitivity. Thus, the detection limit achieved was more than two times lower than that of the amplitude detection. In terms of CFU, phase detection was sensitive even at 200 CFU, while amplitude detection was applicable at 3000 CFU.

Mobility and transport of pharmaceuticals nalidixic acid and niflumic acid in saturated soil columns

Pharmaceutical compounds often coexist in mixtures rather than as individual entities. However, little is known about their co-adsorption and co-mobility in soil and groundwater. In this study, we investigated the adsorption of a quinolone antibiotic (nalidixic acid, NA) and an anti-inflammatory agent (niflumic acid, NFA) onto two soils from France and Sweden in water-saturated soil columns. Despite its lower hydrophobicity, adsorption of NA is much greater than NFA, which can be ascribed to the presence of both carbonyl and carboxylic groups in NA molecule. The data suggest that chemical adsorption to soil components can mainly take place through hydrogen bonding and surface complexation mechanisms, prevailing over hydrophobic interactions. Accordingly, more sorption of NA and NFA was observed in the Swedish soil because it contains more clay content, and much greater Al and Fe contents than the French soil. Injection of NA/NFA mixture in the column did not modify the breakthrough behavior compared to single systems, although cooperative adsorption was observed under static batch conditions. Ca2+ inhibited NA adsorption by forming a soluble NA-Ca2+ complex but promoted NFA adsorption both in single and binary systems. Their mobility in soil columns was well predicted using a new transport model that accounts for both kinetics and binding reactions of NA and NFA to soil constituents. This work will help in accurately predicting the mobility of coexisting pharmaceutical compounds in soils.

Single-Atom Site SERS Chip for Rapid, Ultrasensitive, and Reproducible Direct-Monitoring of RNA Binding.

Ribonucleic acids (RNA) play active roles within cells or viruses by catalyzing biological reactions, controlling gene expression, and communicating responses to cellular signals. Rapid monitoring RNA variation has become extremely important for appropriate clinical decisions and frontier biological research. However, the most widely used method for RNA detection, nucleic acid amplification, is restricted by a mandatory temperature cycling period of ≈1 h required to reach target detection criteria. Herein, a direct detection approach via single-atom site integrated surface-enhanced Raman scattering (SERS) monitoring nucleic acid pairing reaction, can be completed within 3 min and reaches high sensitivity and extreme reproducibility for COVID-19 and two other influenza viruses' detection. The mechanism is that a single-atom site on SERS chip, enabled by positioning a single-atom oxide coordinated with a specific complementary RNA probe on chip nanostructure hotspots, can effectively bind target RNA analytes to enrich them at designed sites so that the binding reaction can be detected through Raman signal variation. This ultrafast, sensitive, and reproducible single-atom site SERS chip approach paves the route for an alternative technique of immediate RNA detection. Moreover, single-atom site SERS is a novel surface enrichment strategy for SERS active sites for other analytes at ultralow concentrations.

Exploration of the intermolecular isoproturon–bovine serum albumin combination: Biophysical and computational prospects

Isoproturon (IPU), a selective systemic herbicide that is frequently applied to eradicate large-leaved weeds and annual grasses in agricultural fields. However, the accumulation of IPU residues during food production might negatively affect on human and animal health. To comprehend the impact of IPU on the mankind and environment, the interaction analysis of IPU with plasma protein is crucial. This work used a variety of techniques, including fluorescence, UV–vis absorption, computational docking and dynamics simulation to extensively examine the combination of IPU with bovine serum albumin (BSA) under typical physiological settings. IPU quenched the BSA fluorescence and form the IPU–BSA complex through a static process. A weak binding affinity was anticipated (binding constant = 4.68–2.48 × 103 M−1) for IPU–BSA interaction. Thermodynamic results revealed that the IPU–BSA binding reaction was a spontaneous process, predominantly governed by hydrogen bonds, van der Waals and hydrophobic forces, which was well supported by molecular docking analysis. Synchronous and three-dimensional fluorescence spectral results exhibited microenvironmental fluctuations near the protein’s Trp and Tyr residues with added IPU, but inclusion of IPU to BSA was observed to enhance the protein’s thermal constancy. Site marker displacement results demonstrated that IPU desirably binds to BSA at site II. An in silico findings also unveiled the primary binding arrangement of IPU was placed at site II of BSA and surrounded by hydrophobic and polar residues. Molecular dynamics simulation results suggested the IPU–BSA complex persisted compact and stable.

Optimizing the Activation Energy of Reactive Intermediates on Single-Atom Electrocatalysts: Challenges and Opportunities.

Single-atom catalysts (SACs) have made great progress in recent years as potential catalysts for energy conversion and storage due to their unique properties, including maximum metal atoms utilization, high-quality activity, unique defined active sites, and sustained stability. Such advantages of single-atom catalysts significantly broaden their applications in various energy-conversion reactions. Given the extensive utilization of single-atom catalysts, methods and specific examples for improving the performance of single-atom catalysts in different reaction systems based on the Sabatier principle are highlighted and reactant binding energy volcano relationship curves are derived in non-homogeneous catalytic systems. The challenges and opportunities for single-atom catalysts in different reaction systems to improve their performance are also focused upon, including metal selection, coordination environments, and interaction with carriers. Finally, it is expected that this work may provide guidance for the design of high-performance single-atom catalysts in different reaction systems and thereby accelerate the rapid development of the targeted reaction.

Engineered DNA bonsai system for ultrasensitive wide-field determination and intracellular dynamic imaging of protein with tunable dynamic range and sensitivity

Herein, an engineered DNA bonsai system was assembled using DNA nanocube (DNC) as pot and a group of DNA recognition hairpins (RHpn, n = 1–5) as plants for ultrasensitive wide-field detection and dynamic intracellular imaging of matrix metalloproteinase-2 (MMP-2) with tunable dynamic range and sensitivity. Impressively, by changing the stem length of the RHpn (n = 1–5), the thermodynamic parameter free energy (△G) of RHpn was regulated to control the binding reaction between RHpn and output target (OT) (like changing the plants species of bonsai, Bonsai 4-RHpn, n = 1–5). When the △G of RHpn was low, the target detection in high concentration range could be achieved. Conversely, the target detection within the low concentration range also could be realized with the high △G of RHpn. Therefore, the developed biosensing platform based on the engineered DNA bonsai system could achieve the ultrasensitive wide-field determination of MMP-2 with 150000-fold tuned detection sensitivity. Meanwhile, by virtue of the spatial restriction effect of DNC to vary the loaded number and the local concentration of RHp1 (like changing the plants density of bonsai, Bonsai n-RHp1, n = 1–4), the kinetic property of the binding process between RHp1 and OT could be manipulated, in which a low substrate concentration leaded to a low reaction efficiency and a high local concentration resulted in a quick reaction rate with high collision probability. Moreover, the designed DNA bonsai system with the highest local concentration (Bonsai 4-RHp1) could achieve rapid detection of the target MMP-2, which easily conquered the main predicaments of dynamic detection methods: limited dynamic range and low detection efficiency. Most importantly, the programmable DNA bonsai system had been successfully applied in ultrasensitive and high-efficient dynamic visualization of protein MMP-2 in living cells, which could not only make it possible to quickly and precisely monitor disease related proteins with tiny changes at different concentration ranges, but also possess tremendous potential to provide high-precision disease information at different stages in disease diagnosis and prognosis monitoring.

Isothermal titration calorimetry analysis of the binding between the maltodextrin binding protein malE of Staphylococcus aureus with maltodextrins of various lengths

Staphylococcus aureus (S. aureus), a Gram-positive bacterium, causes a wide range of infections, and diagnosis at an early stage is challenging. Targeting the maltodextrin transporter has emerged as a promising strategy for imaging bacteria and has been able to image a wide range of bacteria including S. aureus. However, little is known about the maltodextrin transporter in S. aureus, and this prevents new S. aureus specific ligands for the maltodextrin transporter from being developed. In Gram-positive bacteria, including S. aureus, the first step of maltodextrin transport is the binding of the maltodextrin-binding protein malE to maltodextrins. Thus, understanding the binding affinity and characteristics of malE from S. aureus is important to developing efficient maltodextrin-based imaging probes. We evaluated the affinity of malE of S. aureus to maltodextrins of various lengths. MalE of S. aureus (SAmalE) was expressed in E. coli BL21(DE3) and purified by Ni-NTA resin. The affinities of SAmalE to maltodextrins were evaluated with isothermal titration calorimetry. SAmalE has low affinity to maltose but binds to maltotriose and longer maltodextrins up to maltoheptaose with affinities up to Ka = 9.02 ± 0.49 × 105 M−1. SAmalE binding to maltotriose-maltoheptaose was exothermic and fit a single-binding site model. The van't Hoff enthalpy in the binding reaction of SAmalE with maltotriose was 9.9 ± 1.3 kcal/mol, and the highest affinity of SAmalE was observed with maltotetraose with Ka = 9.02 ± 0.49 × 105 M−1. In the plot of ΔH-T*ΔS, the of Enthalpy−Entropy Compensation effect was observed in binding reaction of SAmalE to maltodextrins. Acarbose and maltotetraiol bind with SAmalE indicating that SAmalE is tolerant of modifications on both the reducing and non-reducing ends of maltodextrins. Our results show that unlike ECmalE and similar to the maltodextrin binding protein of Streptococci, SAmalE primarily binds to maltodextrins via hydrogen bonds. This is distinct from the maltodextrin binding protein of Streptococci, SAmalE that binds to maltotetraiol with high affinity. Understanding the binding characteristics and tolerance to maltodextrins modifications by maltodextrin binding proteins will hopefully provide the basis for developing bacterial species-specific maltodextrin-based imaging probes.

Convection-Diffusion-Adsorption Model for the Description of the Analyte-Binding Reactions on a Membrane

The performance of many biomedical assays strongly depends on the transport of analyte molecules to the surface where the binding reactions occur. In some experimental systems, liquid flow can drastically improve the detection limit and decrease the analysis time. This is true for many membrane-based analyses, such as dot-blotting and immunofiltration, in which the sample flows through a porous membrane and adsorbs onto the polymer surface in the pores. Here, we use the convection-diffusion-adsorption equation to calculate the amount of the adsorbed analyte as a function of time. The analyte-binding efficiency is compared for the two sample loading procedures—pressure-driven flow and incubation. Computation shows that when the liquid flow rate reaches a certain threshold, the pressure-driven flow setup ensures higher analyte adsorption than incubation. The convection can drastically decrease the time necessary to capture a small detectable amount of the analyte. However, the infinite increase of the flow rate seems useless because it cannot overcome the kinetic limitation of the adsorption. The model proposed here is in good agreement with the experimental data and can be valuable for the development of membrane-based biosensors.

In silico identification and molecular mechanism of novel egg white-derived tyrosinase inhibitory peptides

This study aimed to identify novel tyrosinase inhibitory peptides from egg white proteins including ovalbumin, ovotransferrin and ovomucoid. Peptides GDVA and DEK were identified using computer-aided virtual screening and in vitro tyrosinase inhibition experiments. Especially, peptide DEK exhibited the strongest tyrosinase inhibitory capacity with IC50 value of 0.205 ± 0.07 mmol L−1. Molecular docking and isothermal titration calorimetry analysis (ITC) were performed to explore the molecular mechanism. The results revealed that two peptides interacted with key residues of tyrosinase mainly by hydrogen bonding and hydrophobic interaction. The binding reactions of these peptides with tyrosinase were spontaneous, endothermic and entropy driven. Furthermore, the structure of two peptide-tyrosinase complexes was compact and stable during the molecular dynamic simulation. These findings indicated that egg white-derived peptide DEK had potential as tyrosinase inhibitory peptide.

Revealing the ACE receptor binding properties and interaction mechanisms of salty oligopeptides from Stropharia rugosoannulata mushroom by molecular simulation and antihypertensive evaluation.

The salty oligopeptides from Stropharia rugosoannulata have been proven to be potential ACE inhibitors. To investigate the ACE receptor binding properties and interaction mechanisms of salty oligopeptides, the molecular interaction, dynamics simulation, and antihypertensive evaluation cross-validation strategy were employed to reveal the oligopeptides' binding reactions and modes with the ACE receptor. Single oligopeptide (ESPERPFL, KSWDDFFTR) had exothermic and specific binding reactions with the ACE receptor, driven by hydrogen bonds and van der Waals forces. The coexistence of the multiple oligopeptide molecules did not produce the apparent ACE receptor competition binding reactions. The molecular dynamics simulation verified that the two oligopeptides disturbed the ACE receptor's different residue regions. Both oligopeptides could form stable complexes with the ACE receptor. Based on the classification of 50 oligopeptides' binding modes, ESPERPFL and KSWDDFFTR belonged to different classes, and their receptor binding modes and sites complemented, resulting in a potential synergistic effect on ACE inhibition. The antihypertensive effect of KSWDDFFTR and its distribution in the body were evaluated using SHR rats orally and ICR mice by tail vein injection, and KSWDDFFTR had antihypertensive effects within 8 h. The study provides a theoretical basis for understanding salty oligopeptides' ACE receptor binding mechanism and their antihypertensive effects.

Exploring cheese and red wine pairing by an in vitro simulation of tasting

The cheese wine pairing is a beloved combination subject to a certain subjectivity due to sensorial, psychological, chemical, and cultural factors. This work represents a first attempt to explore the in vitro interactions between cheese, wine, and saliva to objectively measure the pairing. Two experimental red wines obtained from the same grape cultivar and four different cheeses were studied for their composition. Binding reactions between wine and cheese were carried out in three simulated tasting trials and, after precipitation, the wine phenolic content, Saliva Precipitation Index (SPI), and total proteins were evaluated. The optimal pairing (OP) was calculated considering the decrease in salivary and cheese proteins by wine, defined as the cleansing effect; the decrease in astringency due to the cheese, measured by the SPI, and the coating fat which would remain in mouth after eating a piece of cheese. Based on obtained results, the semi-hard cheese was identified as the best pairing option for the two experimental red wines. The differences in the phenolic content between the two wines were instead not enough to show a significant influence on the OP. The in vitro cheese wine pairing can contribute to understanding of wine tasting but it is only a part of the puzzle. However, this first contribution paves the way for additional studies on the molecular and chemical interactions involved in aroma and textural perception in simulated trials.

Performance and characterization of snail adhesive mucus as a bioflocculant against toxic Microcystis

Toxic Microcystis blooms are widespread in aquatic bodies, posing major threats to aquatic and human life. Recently, bioflocculants have attracted considerable attention as a promising biomaterial for Microcystis management. In search of a novel organism that can produce an efficient bioflocculant for controlling harmful algae sustainably, the native gastropod Cipangopaludina chinensis was co-cultured continuously with toxic Microcystis under different initial algal cell densities. The bioflocculation effect of snail mucus on toxic Microcystis, microcystin removal, and toxin accumulation in snails was investigated. In addition, the properties of the adhesive mucus were characterized using microscopic, X-ray diffraction, infrared spectroscopy, and polysaccharide and proteome analyses. Microcystis cells were captured and flocculated by the snail mucus; removal efficiencies of up to 89.9% and 84.8% were achieved for microalgae and microcystin-leucine arginine (MC-LR), respectively, when co-cultured with C. chinensis for only one day. After nine-day exposure, less than 5.49 µg/kg DW microcystins accumulated in the snails, indicating safety for human consumption. The snail mucus contained 104.3 µg/mg protein and 72.7 µg/mg carbohydrate, which provide several functional groups beneficial for Microcystis bioflocculation. The main monosaccharide subunits of polysaccharides are galactose, galactosamine, glucosamine, fucose, glucose, and mannose. Most of them are key components of polysaccharides in many bioflocculants. Gene Ontology analysis indicated the protein enrichment in binding processes and catalytic activity, which may account for Microcystis bioflocculation via protein binding or enzymatic reactions. The findings indicate that native C. chinensis secretes adhesive mucus that can act as bioflocculant for toxic Microcystis from ambient water and can be an effective and eco-friendly tool for Microcystis suppression.