S-S Bond Research Articles

Reduced fat content of fried batter-breaded fish nuggets by adding dietary fibers: Insight into wheat starch and gluten conformations, fiber properties and anti-fat absorption capacities

Dietary fibers with excellent processing characteristics and water-holding capacity garnered significant attention in low-fat fried products manufacturing, but further research is lacking to elucidate fat reduction mechanisms. Three dietary fibers were added to the batter of fried batter-breaded fish nuggets, the increased maximum wavelength, fluorescence intensity, surface hydrophobicity value, and S-S/free-SH ratio revealed the enhanced exposure and interaction of hydrophobic groups within gluten. Conversion from both -SH into S-S bonds, and α-helix into β-turn confirmed the establishment of the gluten gel network and a substantially increased gel strength. X-ray diffraction demonstrated the inhibition of amylose-lipid complex formation due to the competitive amylose binding to dietary fiber. Finally, reduced oil effects were evident in surface and penetrated oil contents and oil distribution fluorescence diagram. The work clarified the interactions among dietary fiber, wheat starch and gluten, indicating the composite gel network formation and the crust characteristics alterations, ultimately inhibiting oil penetration.

High-intensity ultrasound-modified Jerusalem artichoke leaf protein for stabilizing corn oi-in-water emulsion and Enhacing curcumin delivery

Jerusalem artichoke leaf protein (JALP) has limited applications because of its dark color, even though Jerusalem artichoke is a cash crop. This study utilized high-intensity ultrasound (HIUS) (≤ 600 W) to modify the physicochemical characteristics and functional properties of JALP. Compared with the JALP, all the HIUS-treated JALP (UJALP) samples had a lighter brown color, higher absolute ζ-potential value, lower Z-average size, higher surface hydrophobicity, higher water solubility, lower turbidity, more -SH group, and higher water-holding, oil-holding, emulsifying and foaming capacities. The HIUS treatment disrupted certain non-covalent and SS bonds, promoted protein depolymerization, change protein secondary structures, causing partial unfolding of protein and exposure of some charged groups, hydrophobic groups and chromophores (like tryptophan and tyrosine). The UJALP-stabilized corn oil-in-water emulsions (UJALPEs) were more stable than the JALP-stabilized emulsion (JALPE). The bioaccessibility of curcumin in the JALPE (56.38 %) was significantly lower than in the UJALPE-600 W (64.59 %).

The curious case of S4N4 − A reinvestigation

This work employs quantum chemical methods to explore electronic properties and bonding of the S4N4 molecule. We utilized calculations of multidimensional off-nucleus magnetic shielding, anisotropy of the induced current density (ACID), natural bond orbitals (NBOs), and atoms in molecules (AIM). The unique S4N4 system comprises bent bonding, absence of NN, weakness in the centers of SS bonds, and polar SN bonds. Our findings uncover coexisting of both electron localization and delocalization in S4N4. The magnetic analysis discloses curved connections between the nitrogen atoms and the SS bonds, drawing possible electron delocalization pathways as two pyramid-like regions of magnetic activity. Our magnetic calculations were performed at DFT/GIAO-B3LYP using Jorge-TZP-DKH and 6-311++G(2d,2p) basis sets. No remarkable qualitative differences were noticed between the obtained magnetic features from these two basis sets. Capturing the magnetic details associated with structural features shows superiority of ZZ component of the magnetic shielding tensor (σzz(r)) over the isotropic magnetic shielding (σiso(r)).

Enhancing the cytotoxicity of immunotoxins by facilitating their dissociation from target receptors under the reducing conditions of the endocytic pathway

Immunotoxins (ITs) are recombinant chimeric proteins that combine a protein toxin with a targeting moiety to facilitate the selective delivery of the toxin to cancer cells. Here, we present a novel strategy to enhance the cytosolic access of ITs by promoting their dissociation from target receptors under the reducing conditions of the endocytic pathway. We engineered monobodySS, a human fibronectin type III domain-based monobody with disulfide bond (SS)-containing paratopes, targeting receptors such as EGFR, EpCAM, Her2, and FAP. MonobodySS exhibited SS-dependent target receptor binding with a significant reduction in binding under reducing conditions. We then created monobodySS-based ITs carrying a 25 kDa fragment of Pseudomonas exotoxin A (PE25), termed monobodySS-PE25. These ITs showed dose-dependent cytotoxicity against target receptor-expressing cancer cells and a wider therapeutic window due to higher efficacy at lower doses compared to controls with SS reduction inhibited. ERSS/28-PE25, with a KD of 28 nM for EGFR, demonstrated superior tumor-killing potency compared to ER/21-PE25, which lacks an SS bond, at equivalent and lower doses. In vivo, ERSS/28-PE25 outperformed ER/21-PE25 in suppressing tumor growth in EGFR-overexpressing xenograft mouse models. This study presents a strategy for developing solid tumor-targeting ITs using SS-containing paratopes to enhance cytosolic delivery and antitumor efficacy.

Photopolymerization initiated by p-diethylene glycol monomethyl ether cinnamyl formamide-based disulfide under 455 nm LED with minimized volume shrinkage

This study introduces a novel p-diethylene glycol monomethyl ether cinnamyl formamide-based disulfide monomer, N,N′-(disulfanediylbis(2,1-phenylene)) bis(4-(4-(2-(2-methoxyethoxy)ethoxy) phenyl)-2-oxobut-3-enamide) (Mp-BSCF), designed to reduce the volume shrinkage of photosensitive resins and initiate monomer polymerization under 455 nm LED light irradiation. The photochemical properties and photoinitiation efficiency of Mp-BSCF are systematically investigated using UV–vis absorption spectroscopy, electron paramagnetic resonance (EPR) and real-time infrared spectroscopy. Although its weak absorption around 455 nm, Mp-BSCF can generate arylthiyl radicals under 455 nm LED irradiation, and then effectively initiate the polymerization of triethylene glycol dimethacrylate (TEGDMA)/A glycerolate dimethacrylate (Bis-GMA) system. Increasing Mp-BSCF addition enhances the final double bond conversion and maximum polymerization rate of the TEGDMA/Bis-GMA system, reaching up to 82.0 % and 2.02 % s−1, respectively. Notably, Mp-BSCF significantly reduces the volume shrinkage of the photopolymerization system, with the addition of 10 % Mp-BSCF resulting in a 50 % reduction compared to the control system. This reduction is attributed to the dynamic reversible nature of the SS bond “breaking-recovery” and the intermolecular hydrogen bond interaction. Additionally, Mp-BSCF improves the thermal stability, friction resistance, and hardness of the TEGDMA/Bis-GMA photopolymerization system.

Syntheses, structures, photoelectricity and photocatalysis of Cu(I) iodide hybrids and thiolate derived from dithiodipyridine

Iodocuprate hybrids {[(4,4′-dtdpy)2Cu2I2]·DMA}n (4,4′-dtdpy = 4,4′-dithiodipyridine; DMA = N,N-dimethylacetamide) (1) and [(2,2′-dtdpy)Cu2I2]2 (2,2′-dtdpy = 2,2′-dithiodipyridine) (2) were prepared by reacting CuI and KI using 4,4′-dtdpy and 2,2′-dtdpy as SDAs, respectively, at room temperature. The Cu2I2 aggregates were joined by a μ-4,4′-dtdpy bridging ligand with N-donor atom, and by a 2,2′-dtdpy chelating ligand with N- and S-donor atoms to form a 1-D polymeric complex {[(4,4′-dtdpy)2Cu2I2]·DMA}n and a tetranuclear complex [(2,2′-dtdpy)Cu2I2]2, respectively. The reaction CuI, KI and 2,2′-dtdpy in CH3OH solvent under solvothermal conditions formed a polymeric iodocuprate hybrid [(mmtpy)(Cu2I3)]n (mmtpy+ = 1-methyl-2-(methylthio)pyridinium) (3). 2,2′-dtdpy was converted in situ to the mmtpy+ cation via cleavage of the SS bond and methylation of the N and S atoms in the solvothermal reaction. In compound 3, tetrahedral CuI4 units are connected into a 1-D [Cu2I3]nn− chain by edge- and face-sharing. In the same solvothermal reaction in DMF, the SS bond of 2,2′-dtdpy was cleaved to form a mtpy– anion. The mtpy– anion coordinated to Cu+ ions as a bidentate ligand with N and S-donor atoms to form a hexanuclear thiolate complex [Cu6(mtpy)6] (Hmtpy = 2-mercaptopyridine) (4). A pseudohexagonal prismatic Cu6S6 core is formed in 4. Compounds 1–4 showed strong photocurrent responses with steady current densities in the range of 0.33–0.79 μA·cm−2. Compounds 1–4 are catalytically active in the photodegradation of MB with degradation ratios of 80.5 %, 90.3 %, 100 %, and 84.6 %, respectively, after 120 min of light irradiation.

Dissolution patterns of gold on various structural surfaces in thiosulfate solutions: The effect of interface adsorption on thiosulfate oxidation and gold atom dissociation

Passivation caused by the adsorption and decomposition of thiosulfate on gold surfaces significantly influences the leaching rate of gold. The surface structure often determines the reactivity of an interface. Studying the effects of different surfaces on the decomposition of thiosulfate ions and gold dissolution can provide insights into the passivation formation mechanism. In this study, the oxidation of thiosulfate on different surfaces is investigated using linear voltammetry. The oxidation response of thiosulfate was weaker on granular (1 1 1) and (5 4 1) surfaces than on nanoflakes with (1 1 1) surface. Furthermore, the Tafel test results indicate that the potential for gold dissolution is higher on the granular (1 1 1) and (5 4 1) surfaces, leading to a smaller current value of gold dissolution. Raman spectroscopy indicates that the response signals of the polysulfides and polythionate were stronger on the granular (1 1 1) and (5 4 1) surfaces. The chemical bond changes of thiosulfate adsorbed on different surfaces are studied through molecular simulations based on density functional theory. These results indicate that as the saturation of surface gold atoms decreases, their reaction activity increases, and the bonding effect with thiosulfate ions becomes stronger during adsorption. The changes in the SS bonds in thiosulfate reflect the influence of the different surfaces on their stability. On the (1 1 1) surface, the SS bond changes from the initial 2.102 Å to the adsorbed 2.254 Å, while on the (5 4 1) surface, the SS bond changes to 2.274 Å Although the reaction activity of the granular (1 1 1) and (5 4 1) surfaces is high, the energy barrier for dissociating individual gold atoms from them is higher. The adsorption of sulfur-containing substances on the surface, along with the increased energy barrier for gold dissociation are both factor contributing to the greater difficulty of gold dissolution from granular (1 1 1) and (5 4 1) surfaces.

Multistimuli responsive hydrogels with shape fix/memory capability fabricated from gold nanorod‐conjugated amino acid‐based vinyl polymer networks

AbstractFabricating robust shape‐memory hydrogels that respond to multiple external stimuli is an important challenge in facilitating gel technology for versatile applications. In this study, we report a simple approach for constructing thermo‐, redox‐, and photo‐responsive hydrogels with high mechanical strength and shape fix/memory capability. Upper critical solution temperature (UCST)‐type amino acid‐based hydrogels were facilely prepared by radical copolymerization of N‐acryloyl glycinamide (NAGAm) with cystine‐derived divinyl acrylamides (ionic cystine [NAC] or nonionic cystine‐methyl ester [NACMe]) units at different monomer concentrations (1/2 M). These hydrogels were transparent and exhibited good mechanical strength (tensile strength of 0.3–0.4 MPa and breaking elongation of 400%–700%). All hydrogels showed UCST‐type swelling‐shrinking behaviors based on thermo‐driven reversible hydrogen bonds among the PNAGAm units, and thus could be fixed into variety of shapes and recovered to the original shape by temperature manipulation. The cystine‐based crosslinkers having SS bonds served as efficient redox‐sensitive and gold‐nanorod‐(AuNR)‐adsorbing moieties; thus, AuNR could be conjugated stably and evenly into the PNAGAm/NAC hydrogel. Moreover, upon light‐irradiation, the AuNR‐conjugated hybrid hydrogel exhibited shape‐memory behavior owing to the photothermal effect of the AuNRs. These multiresponsive/functional hydrogels composed of amino acid units have considerable potential for various applications in the fields of soft actuators and biomedicines.

Perilla protein isolate exhibits synergistic techno-functionality through modification via sequential dynamic high-pressure microfluidization and enzymatic hydrolysis

Modification of proteins derived from plant sources is crucial for enabling their versatile applications in the food industry. In the present study, structural and functional properties of individual treated perilla protein isolate (PPI) through dynamic high-pressure microfluidization (DHPM) and enzymatic hydrolysis (EH) was compared with their sequential (DHPM-EH) treatment. Native PPI thick, sharp-edged blocks transformed into a collapsed structure with wrinkles after sequential (DHPM-EH) treatment. The synergistic effect between DHPM and EH, during sequential (DHPM-EH) treatment caused greater reduction (91.9%) in PPI particle size as compared to DHPM (87.3%), and EH (84.5%), which enhanced PPI solubility, even at low pH. Above treatments altered the conformational structure of PPI as evident from changes in surface hydrophobicity, free –SH groups conversion into –SS bonds, ultraviolet absorption and fluorescence intensities changes, and decreased α-helix, while increased β-sheets. The sequential (DHPM-EH) treated PPI showed enhanced foaming capacity (×3.59), as well as increased thermal and colloidal stability.

An electrochemical sensor based on electrochemically activated carbon cloth and poly (o-aminothiophenol) cross-linked nanogold imprinted layer for the determination of tert-butylhydroquinone

In this study, an electrochemical sensor based on MoS2 with enhanced electrochemical signals from electrochemically activated carbon cloth (EACC) electrodes and cross-linked o-aminothiophenol functionalized AuNPs (o-ATP@AuNPs) was developed for the detection of the unsaturated vegetable oil antioxidant tert-butylhydroquinone (TBHQ). In this approach, carbon cloth is activated through the implementation of electrochemical methods, thereby effectively increasing its specific surface area. The resulting EACC, serving as an electrode substrate, enables the growth of additional nanomaterials and enhances conductivity. The incorporation of MoS2 effectively augments the sensitivity of the electrochemical sensor. Subsequently, MIP/MoS2/EMCC is formed via electropolymerization, utilizing TBHQ as the template molecule and o-ATP@AuNPs as the functional monomer. The SS bond of o-ATP ensures a strong and stable connection between MoS2 and o-ATP@AuNPs, thereby facilitating the immobilization of MIP. In addition, the high conductivity possessed by o-ATP@AuNPs could effectively improve the sensitivity of the electrochemical sensor. Under the optimal conditions, MIP/MoS2/EMCC could determine TBHQ in the range of 1 × 10−3 μM to 120 μM by differential pulse voltammetry (DPV) with a detection line of 0.72 nM. The proposed MIP/MoS2/EMCC is expected to be applied in the future for the selective and sensitive detection of TBHQ in vegetable oils.

Chromium‐Catalyzed Reductive Cross‐Coupling to Construct C−SS Bonds from Unactivated Alkyl Electrophiles

AbstractLow‐valent chromium catalysts are cheap and less toxic compared to other transition metal catalysts. Here in, we reported a ligand‐free chromium(III)‐catalyzed manganese reductive cross‐coupling of unactivated alkyl electrophiles, such as alkyl sulfonates and alkyl chlorides, with trisulfide dioxides as thiolation agents to form carbon−sulfur bonds. The powerful method featured ample substrate scope and wide functional group tolerance, constructing a large number of unsymmetrical disulfides under simple conditions.

Oxygen-containing functional groups of activated carbon fibers as efficient oxygen transfer channels for H2S catalytic oxidation at room temperature

Activated carbon fibers (ACFs) with different activation degrees were developed by KOH activation method. And then, series of Na2CO3 loaded ACF catalysts were prepared and tested for H2S catalytic oxidation at room temperature. Among them, Na/ACF-8 presented the highest saturation sulfur capacity (1.22 gH2S/g). Importantly, it was found that COOH, COC/COH and COOCO were the main active oxygen species, and acted as oxygen transfer channels during the reaction. The reaction process mainly involved the dissociation of H2S, the reaction of HS− with C-O bond containing groups to form C-S bonds and sulfur-containing products. Moreover, the oxygen-containing functional groups were just responsible for water generation and the superoxide radical (O2•−) was responsible for SS bond oxidation. The O2•− was activated by ring carbon defects for Na/ACF-6 and Na/ACF-8 catalysts. And the ring carbon defects and ultramicropores were jointly responsible for the activation of O2•− for Na/ACF-2 and Na/ACF-4 catalysts.

Nitrogen-Doped CoP with optimized d-Band center as bidirectional electrocatalyst for high areal capacity of Li-S battery

Lithium polysulfide (LiPSs) shuttle effect and difficulties with Li2S oxidation are hinder the marketization of lithium-sulfur batteries. We suggest using a bidirectional catalyst in the sulfur host to solve these problems. We produced a nitrogen-doped cobalt phosphide (N-CoP@NC) as a sulfur carrier in this work. The introduction of nitrogen into cobalt phosphide enhances the electron transmission speed and forms shorter Co-N bonds. As a result, new defect energy levels are introduced, leading to an increase in the charge number of Co central atoms, which abate the Li-S and SS bonds in Li2S and Li2S4, thereby promoting the oxidation of Li2S during charging, as well as the alteration process of LiPSs during charge and discharge. Additionally, the crystal flaws that result in increased Co-S bond formation help to boost polysulfides' adsorption ability. The Li-S batteries shows outstanding cyclability when paired with this electrocatalyst, demonstrating a minimal capacity degradation rate of only 0.07 % per cycle over 500 cycles at a rate of 0.5C. As a result, incorporating anion doping in the host emerges as a promising method for crafting materials tailored for Li-S batteries.

Heat-induced agglomeration of water-soluble cod proteins toward gelled structures

Cod proteins (CPs) have potential applications in designing desirable gel-based products, and this study aimed to unravel their heat-induced aggregation pattern and further probe the roles in protein gels. SDS-PAGE analysis indicated that high-precipitation-coefficient aggregates (HPCAs) of CPs aggregates were composed of considerable polymers of myosin heavy chains and actin, and their low-precipitation-coefficient aggregates (LPCAs) contained myosin light chains and tropomyosin. Studies from correlation analysis between the structure and aggregation kinetics revealed that the generation of β-sheet and SS bonds were responsible for their spontaneous thermal aggregation induced by heating temperature and protein concentration, respectively. Additionally, as protein denaturation ratio increased, more and larger HPCAs were formed, which was evidenced driving the network formation of protein gels and resulting in higher storage modulus (G') values. These novel findings may be applicable to other animal proteins for better tailoring the manufacturing of muscle gel-based products.

AChE activity self-breathing control mechanisms regulated by H2Sn and GSH: Persulfidation and glutathionylation on sulfhydryl after disulfide bonds cleavage

Hydrogen sulfide (H2S), or dihydrogen sulfane (H2Sn), acts as a signal molecule through the beneficial mechanism of persulfidation, known as the post-translational transformation of cysteine residues to persulfides. We previously reported that Glutathione (GSH) could regulate enzyme activity through S-desulfurization or glutathionylation of residues to generate protein-SG or protein-SSG, releasing H2S. However, little is known about the mechanisms by which H2Sn and GSH affect the disulfide bonds. In this study, we provide direct evidences that H2Sn and GSH modify the sulfhydryl group on Cys272, which forms disulfide bonds in acetylcholinesterase (AChE), to generate Cys-SSH and Cys-SSG, respectively. Glutathionylation of disulfide is a two-step reaction based on nucleophilic substitution, in which the first CS bond is broken, then the SS bond is broken to release H2S. H2Sn and GSH controlled self-breathing motion in enzyme catalysis by disconnecting specific disulfide bonds and modifying cysteine residues, thereby regulating AChE activity. Here, we elucidated H2Sn and GSH mechanisms on disulfide in the AChE system and proposed a self-breathing control theory induced by H2Sn and GSH. These theoretical findings shed light on the biological functions of H2Sn and GSH on sulfhydryl and disulfide bonds and enrich the theory of enzyme activity regulation.

Characterisation of a phosphatase-like nanozyme developed by baking cysteine and its application in reviving mung bean sprouts damaged by ash

Baked cysteine is mainly composed of cystine, a dimer with a SS bond. It acts as a nanozyme with phosphatase activity and an allosteric mechanism, repairs damage caused by ash to plant roots and germination and synergically combines with chlorophyll.

Copper-catalyzed alkynyldisulfuration of arynes: efficient access to unsymmetrical disulfides

This article investigates a copper-catalyzed alkynyl disulfuration reaction of arynes formed in situ that generates o-alkynyl aryl disulfides via the formation of one C–C bond and one C–SS bond in one pot.

Seleno-relaxin analogues: effect of internal and external diselenide bonds on the foldability and a fibrosis-related factor of endometriotic stromal cells.

Human relaxin-2 (H2 relaxin) is a peptide hormone of about 6 kDa, first identified as a reproductive hormone involved in vasoregulation during pregnancy. It has recently attracted strong interest because of its diverse functions, including anti-inflammatory, anti-fibrotic, and vasodilatory, and has been suggested as a potential peptide-based drug candidate for a variety of diseases. Mature H2 relaxin is constituted by the A- and B-chains stabilized by two interchain disulfide (SS) bridges and one intrachain SS linkage. In this study, seleno-relaxins, SeRlx-α and SeRlx-β, which are [C11UA,C11UB] and [C10UA,C15UA] variants of H2 relaxin, respectively, were synthesized via a one-pot oxidative chain assembly (folding) from the component A- and B-chains. The substitution of SS bonds in a protein with their analogue, diselenide (SeSe) bonds, has been shown to alter the physical, chemical, and physiological properties of the protein. The surface SeSe bond (U11A-U11B) enhanced the yield of chain assembly while the internal SeSe bond (U10A-U15A) improved the reaction rate of the folding, indicating that these bridges play a major role in controlling the thermodynamics and kinetics, respectively, of the folding mechanism. Furthermore, SeRlx-α and SeRlx-β effectively reduced the expression of a tissue fibrosis-related factor in human endometriotic stromal cells. Thus, the findings of this study indicate that the S-to-Se substitution strategy not only enhances the foldability of relaxin, but also provides new guidance for the development of novel relaxin formulations for endometriosis treatment.

Exploration of the structural mechanism of hydrogen (H2)-promoted horseradish peroxidase (HRP) activity via multiple spectroscopic and molecular dynamics simulation techniques

Horseradish peroxidase (HRP) is an enzyme that is widely used in various fields. In this study, the effects of molecular hydrogen (H2) on the activity and structural characteristics of HRP were investigated by employing multiple spectroscopic techniques, atomic force microscopy (AFM) and molecular dynamics (MD) simulations. The results demonstrated that H2 could enhance HRP activity, especially in 1.5 mg/L hydrogen-rich water (HRW). The structural analysis results showed that H2 might alter HRP activity by affecting the active sites, secondary structure, hydrogen bonding network, CS groups, and morphological characteristics. The MD results also confirmed that H2 could increase the FeN bond distance in the active site, affect the secondary structure, and increase the number of hydrogen bonds. The MD results further suggested that H2 could increase the number of salt bridges, and lengthen the SS bonds in HRP. This study primarily revealed the mechanism by which H2 enhances the HRP activity, providing insight into the interactions between gas and macromolecular proteins. However, some of the results obtained via MD simulations still need to be verified experimentally. In addition, our study also provided a new convenient strategy to enhance enzyme activity.

Alterations in the multilevel structure and depolymerization behavior of gluten induced by selenium in fermented dough

This study was conducted to evaluate the alterations of multilevel structure of gluten induced by selenium (Se) and their relationship with the properties of the fermented dough. The results of molecular weight distributions indicated that the degree of gluten aggregation decreased as the Se content in the fermented dough increased. Moreover, the elevated Se content led to a higher percentage of β-sheet in the dough proteins, indicating a more stable structure after depolymerization. Intermolecular interactions indicated that Se disrupted covalent cross-linking between gluten by affecting disulfide (SS) bonds. The levels of glutathione (GSH), free sulfhydryl and SS bond in the dough increased with increasing Se content. This suggested that more GSH was produced by Se induced yeast, which reacted with intermolecular SS in gluten, resulting in reduced gluten cross-linking. Meanwhile, Se affected the viscoelasticity and enhanced the height of the fermented dough. Improved quality of the steamed bread was found with even pore distributions and reduced hardness. This study has the potential to expand the application of Se in the fermented food industry and offer practical ways to increase Se consumption in Se-deficient areas.