Search Results (183)

Infertility is a global health problem, with male factors contributing to nearly half of all cases. Up to 30% of male infertility is classified as idiopathic, in part because routine semen analysis does not assess sperm fertilizing competence. Capacitation is a complex process that endows spermatozoa with the competence to fertilize the oocyte, and it depends on oxidant-driven phosphorylation events. These events include increased PKA substrate and tyrosine phosphorylation, which promote hyperactivated motility and the acrosome reaction. These pathways are normally restrained by decapacitation factors that must be relieved in the female reproductive tract before capacitation can proceed. Protein CoAlation is an antioxidant modification of protein thiols through a disulfide bond with coenzyme A (CoASH). We previously detected protein CoAlation in human spermatozoa and observed that its levels decline during capacitation, but its function was unknown. We hypothesized that protein CoAlation functions as a decapacitation mechanism that prevents redox signalling, enabling oxidative activation of phosphorylation events during capacitation. Using spermatozoa from healthy human donors, we leveraged subcellular fractionation, immunocytochemistry, computer-assisted sperm analysis (CASA), and immunoblotting to determine the sperm protein CoAlation profile, assess CoASH biosynthetic enzymes, and test how pharmacological modulation of CoAlation levels influences capacitation. CoAlated proteins were distributed across intracellular sperm compartments, and spermatozoa possess the CoASH biosynthetic enzymes PANK2 and CoASY, indicating an intrinsic capacity for CoAlation. Inhibition of CoASH biosynthesis reduced CoAlation and enhanced PKA substrate phosphorylation, tyrosine phosphorylation, hyperactivated motility, and the progesterone-induced acrosome reaction under capacitating conditions. Pantothenic acid supplementation increased CoAlation and suppressed these processes without impairing viability or baseline motility. These findings indicate that high levels of protein CoAlation in several protein bands are a pre-existing feature of the non-capacitated state that restrains the redox-regulated events of capacitation and that its decline is required to permit sperm capacitation. CoAlation levels may emerge as a biomarker of sperm capacitation and fertilizing competence. Full article

Under alkaline conditions, most commonly used preservatives exhibit limited efficacy and fail to meet the preservation requirements of coated tofu. This study aims to investigate the effects of metal-phenolic networks (MPNs) on quality deterioration, protein oxidation, conformation, and gel microstructure of coated tofu during cold storage (4 °C and 10 °C). The results showed that, compared with the untreated control group, MPNs treatment effectively inhibited protein oxidation, alleviated quality deterioration, delayed the degradation of color and texture, and reduced protein degradation, as evidenced by soluble protein contents that were 63.55% (4 °C) and 66.65% (10 °C) lower than those of the control group after 20 days of storage. MPNs treatment also improved the orderliness and stability of the protein secondary structure. In addition, electrophoretic analysis showed that MPNs markedly retarded the decline in band optical density of the 11S protein A subunit by 96.19% and 97.28% at 4 °C and 10 °C, respectively, and suppressed the increase in the B subunit by 13.28% and 73.20%, respectively. Moreover, MPNs treatment helped maintain a more compact gel network. Based on physicochemical characterization and Pearson correlation analysis, the preservative effect of MPNs on coated tofu under alkaline conditions was elucidated, revealing the internal correlation between the inhibition of quality deterioration and the regulation of protein oxidation. Specifically, MPNs mitigate protein disulfide bond loss, increase the β-sheet content, preserve the natural protein conformation and the relative proportion of 11S subunits, stabilize the gel microstructure, and thereby achieve quality preservation. These findings provide theoretical support and strategic reference for the development of preservation technologies for alkaline high-protein gel foods. Full article

Bacterial β-barrel pore-forming toxins, including Staphylococcus aureus α-toxin (Hla) and Bacillus cereus toxins hemolysin II (HlyII) and cytolytic toxin K2 (CytK-2), are secreted by bacterial cells as water-soluble monomers. These monomers assemble within lipid bilayers to form cylindrical pores, leading to lysis of target eukaryotic cells. We created mutant forms of these toxins that, based on the results of X-ray structural analysis of Hla and the prediction of the 3D structure of HlyII and CytK2, can form intramolecular disulfide bonds in monomers. The substitutions were made in the region responsible for toxin insertion into the target membrane. The mutant forms reversibly altered their hemolytic activity depending on the presence of reducing reagents and were non-toxic when injected into experimental animals. The immune response to injection of the mutant forms of Hla and CytK-2 toxins resulted in higher antibody titers against the wild-type toxins and a higher level of immunological memory than with injection of the HlyII mutant. The mutant form of CytK-2 demonstrates the properties of a prototype vaccine, as immunization with this protein protects animals against the effects of the wild-type toxin. Full article

Dynamic covalent bonds are commonly used to maintain the self-healing properties of polyurethanes and facilitate resource recycling. However, relying on a single type of dynamic covalent bond often makes it difficult to effectively regulate both mechanical and self-healing properties across a wide temperature range. In this study, a self-synthesized chain extender containing disulfide bonds was introduced into a polyurethane system, leading to the development of a novel dual-dynamic covalent bond self-healing polyurethane (SSDA-PU). Innovatively, this SSDA-PU demonstrates self-healing properties across a wide temperature range. The successful synthesis of the chain extender and the incorporation of both disulfide bonds and Diels–Alder (DA) bonds were confirmed using FTIR and Raman spectroscopy. The physical characteristics and self-healing performance were comprehensively evaluated through multi-scale testing and characterization, including thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), hardness testing, mechanical tensile tests, and self-healing experiments. The underlying synergistic self-healing mechanism was subsequently elucidated. Findings showed that a higher R-value (isocyanate index) in SSDA-PU leads to over-crosslinking, while an R-value of 1.7 achieves the best overall mechanical performance, with tensile strength and elongation at break reaching 21.1 MPa and 755.17%, respectively. Additionally, SSDA-PU demonstrated the capacity for multiple healing cycles, with an initial self-healing efficiency of 90.38%, which remained notably high at 59.21% even after three damage-healing cycles. Importantly, SSDA-PU exhibited healing capabilities even at relatively low temperatures. Cracks in SSDA-PU can be effectively repaired through the synergistic action of disulfide bond exchange, hydrogen bond dissociation, and thermally reversible DA reactions. SSDA-PU also shows excellent recyclability, offering valuable insights for the practical engineering application of functional polyurethanes. Full article

Non-specific lipid transfer proteins (nsLTPs) play a crucial role in lipid transport across membranes, contributing to cellular integrity and structural stability. These proteins are characterized by the presence of eight conserved cysteine residues that form four disulfide bonds and a hydrophobic cavity that is essential for lipid binding and transport. Interactions of nsLTPs with diverse ligands enable them to participate in key biological processes, including signal transduction, protein folding, membrane stabilization, and cell wall organization. Additionally, these proteins are integral to plant responses to abiotic and biotic stresses and to developmental processes, including growth, germination, and flowering. The interaction between nsLTPs and plant signaling molecules activates regulatory networks that modulate stress-responsive gene expression, reinforcing plant resilience under adverse conditions. Despite their functional significance, the evolutionary trajectory, subcellular localization, and regulatory mechanisms governing nsLTP expression remain limited, as reflected in previous reviews on nsLTPs. This review provides a comprehensive analysis of nsLTP evolution, roles in plant defense and signaling, functional diversity, updated subcellular localization, and future research directions based on recent findings. Full article

High-moisture extrusion (HME) is critical for plant-based meat analogs with meat-like fibrous structures. To expand HME protein sources, this study explored mung bean protein (MBP) substitution (0–50%, dry basis) effects on structural, textural and functional properties of soy protein concentrate (SPC)–wheat gluten (WG) HME products. At 20% MBP addition, the proteins formed a dense layered fibrous network, and the fibrous degree of the extrudates reached the peak. MBP > 40% disrupted the continuous protein network. The optimal rehydration for 20% MBP dried extrudates was 60 °C for 40 min, preserving fibrous texture. Protein interaction analysis indicated that hydrogen bonds and disulfide bonds played an important role in stabilizing the protein network structure. Overall, MBP can be incorporated into SPC-WG-based HME products to diversify protein sources, providing a feasible strategy for developing high-quality, nutritionally diversified plant-based meats. Full article

Human prostamide/prostaglandin F synthase (PGFS) catalyzes the NADPH-dependent conversion of prostaglandin H₂ (PGH2) to prostaglandin F₂α that plays a key role in regulating intraocular pressure and labor. Despite its physiological importance, structural and biochemical information of the human PGFS has been limited because of difficulties in obtaining sufficient quality of PGFS wild-type crystal and short half-life of PGH2. Here, we report the crystal structure of human PGFS with two active site mutations, C44S/C47S double mutant (DM), which mimics the reduced active form of the CXXC motif of human PGFS. Structural analysis revealed that PGFS DM adopts a typical thioredoxin (Trx)-like fold. Analysis of B-factors and MD simulations reveals that Tyr108–Asp124 is an intrinsically flexible region, devoid of any stabilizing crystal contacts. Unlike canonical Trx-like proteins, Pro167 in PGFS adopts a trans-conformation, inducing a specific Arg40 side chain localization that creates a positive charge near the CXXC motif. Activation of PGFS by reduction of disulfide bond in the CXXC motif enhanced the thermal stability via core stabilization, yet an unexpected increase in the structural disorder was detected with CD spectroscopy, especially upon ligand binding. These findings collectively establish PGFS as a structurally distinct and redox-regulated enzyme. Our results provide novel molecular insights into PGFS as an underexplored but promising therapeutic target. Full article

Human neuroglobin (Ngb) is a globin featuring a disulfide bond (Cys46–Cys55) and a redox-active cysteine residue (Cys120) and plays a dual role in cellular stress responses. In this study, we investigated how wild-type (WT) Ngb and its two mutants, C120S Ngb, in which Cys120 is replaced by serine, and A15C Ngb, which contains an engineered Cys15–Cys120 disulfide bridge, modulate oxidative stress in triple-negative breast cancer (MDAMB231) and hormone receptor-positive breast cancer (MCF-7) cells. In both cell lines, WT Ngb enhanced cell survival under H₂O₂-induced oxidative stress by scavenging reactive oxygen species (ROS) through oxidation of Cys120. In contrast, the C120S and A15C mutants lost this protective capacity and instead promoted apoptosis. Mass spectrometry analysis confirmed the oxidation of Cys120 to sulfenic acid in WT Ngb, whereas both mutants exhibited impaired redox activity, leading to elevated ROS levels, lipid peroxidation, and activation of caspase-9/3. AO/EB staining further revealed that WT Ngb attenuated DNA damage, while the mutants exacerbated apoptosis in both MDAMB231 and MCF-7 cells. These results demonstrate that Cys120 acts as a critical redox switch, dictating whether Ngb exerts cytoprotective or pro-apoptotic effects across different breast cancer cell types. Our findings suggest that WT Ngb may help protect normal tissues during cancer therapy, whereas engineered Ngb mutants could be used to selectively sensitize both triple-negative and hormone receptor-positive breast cancer cells to oxidative damage, offering a novel redox-targeted therapeutic strategy. Full article

Conventional perming relies on oxidative agents that significantly damage hair. The thiol–Michael click perming strategy derived from linear aliphatic diols and diamines has been developed to avoid oxidative damage, but lacks repeatable perming capabilities. In this study, a novel thiol–Michael click perming molecule was proposed for repeatable perming while avoiding oxidative damage. N,N′-bis(maleoyl)-l-cystine (MA2-CySS) was synthesized and characterized through Raman spectroscopy and ¹H NMR with MTT assay demonstrated no cytotoxicity up to 1000 μg/mL. Click reactivity analysis revealed that the reaction reached a plateau after 30 min, with alkaline pH and elevated temperatures significantly enhancing reactivity. MA2-CySS perming achieved efficiency comparable to oxidative perming, exceeding 1300% across three perming cycles. MA2-CySS perming significantly reduced both color change and cuticle damage, as demonstrated by color difference measurements and SEM, while maintaining superior mechanical properties as revealed by tensile property tests. Raman spectroscopy demonstrated that MA2-CySS perming better preserves hair keratin’s secondary structure, maintaining superior α-helix content at 27.50% versus 24.35%, exhibiting higher disulfide bond retention at 85% versus 72%, and showing gauche–gauche–gauche to trans–gauche–trans conformational conversion at 9% versus 6%. This study demonstrates that repeatable perming via thiol–Michael click reaction represents a significant advancement in perming methodology. Full article

Solute carriers (SLCs) mediate cell- and organelle-specific import and export of nutrients and metabolites required for every biochemical process that occurs in a cell. Functional studies have ascribed activities to many human genes annotated as SLCs, but more than 100 SLCs remain orphans. Here, we applied a set of computational tools to characterize the orphan carriers SLC35F4 and SLC35F5. Phylogenetic analysis grouped SLC35F4 sister to SLC35F3, a suspected thiamine transporter, in a clade with SLC35F5, and distinct from an SLC35F6/2/1 clade. Transcriptome datasets revealed a restricted function for SLC35F4 in the cerebellum, in contrast to the more widespread distribution of SLC35F5. Gene ontology identified the Golgi apparatus as the likely residence of both transporters. Conceptual docking of 71 candidate substrates predicted high affinities of SLC35F4 (10–40 nM) and SLC35F5 (0.1–0.4 nM) for flavin adenine dinucleotide (FAD), straddling that of the known FAD transporter SLC25A32 (2–4 nM), while returning much lower affinities (by 30–fold or more) for all other tested substrates. Docking to SLC35F3 returned low affinity for both FAD and thiamine as candidate substrates. Thus, SLC35F4 and SLC35F5 but not closely related SLC35F3 likely import FAD into the Golgi apparatus, where the cofactor serves as the oxidant for disulfide-bond formation during tissue-specific, post-translational modification of secretory proteins. These findings provide strong direction for the definitive experiments yet needed to confirm the carriers’ subcellular localization, transport activities, and contributions to protein maturation and trafficking. Full article

This study investigated the effects of Auricularia auricula Polysaccharide (AAP) concentrations on the rheological and thermal properties of gluten and its subunit components. We used multiple techniques, including dynamic rheology, differential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FT-IR), free thiol group analysis, and scanning electron microscopy (SEM). The results revealed that AAP increased the storage (G′) and loss (G″) modulus of gluten, glutenin, and gliadin, promoting compact elastic protein networks. DSC and free thiol group analysis demonstrated that AAP enhanced thermal stability and disulfide bond cross-linking in gluten and glutenin, but reduced thermostability and inhibited disulfide formation in gliadin. Secondary structure analysis showed 31.93% and 17.72% increases in α-helix and β-sheet content, respectively, in glutenin at 8% AAP, thereby enhancing the orderliness of the gluten structure and improving structural rigidity, while reducing gliadin’s structural order. Microscopy confirmed AAP narrowed gluten matrix pores, forming uniform honeycomb structures (though high concentrations caused disruption). In summary, AAP primarily stabilizes gluten conformation by modulating glutenin structure, thereby enhancing rheological and thermal properties. Full article

Myofibrillar protein (MP) aggregation in solutions with NaCl concentrations below 0.3 M results in poor solubility. Ultrasound-assisted glutaminase treatment (UGT) was applied to improve MP solubility in a low-salt solution (containing 0.1 M NaCl). The solubility increased with ultrasonic power and time, peaking at 44.34% (480 W, 15 min) and reaching 61% after UGT. Subsequently, the effect of post-sonication heat treatment (60 °C, 30 min) on the physicochemical and structural characteristics of ultrasound-enzyme treated MP (UEMP), prepared under specific ultrasonic conditions (480 W, 20 min), was systematically investigated. The findings revealed that UEMP exhibited higher hydrophobicity, sulfhydryl content, and turbidity, but reduced particle size, ζ-potential, and fluorescence, suggesting disulfide disruption and exposure of hydrophobic residues. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed weakened high-molecular weight bands and intensified low-molecular weight bands. Fourier-transform infrared spectroscopy confirmed these structural rearrangements, with a blue-shifted amide A band and decreased amide I intensity. Heating further increased the hydrophobicity and fluorescence without altering the size, ζ-potential, or molecular weight. The red shift in the amide A band suggests reinforced local ordering. Rheology analysis showed non-Newtonian shear-thinning behavior, which was unchanged by UGT or heating. Collectively, UGT with moderate heating enhances MP solubility and thermal stability by disrupting stabilizing bonds and modulating the structure. Full article

Readily degradable low-dose hydrate inhibitors are of great significance for flow assurance in the petroleum industry. Recently, α-lipoic acid (LA) was shown to undergo ring-opening reaction via reversible addition–fragmentation chain-transfer copolymerization with acrylamides to introduce labile disulfide bonds into the stable vinyl polymer backbone. Here, LA was copolymerized with acryloyl morpholine (AM) to evaluate their performance as kinetic hydrate inhibitors. Degradability was confirmed for the copolymers with 20 mol.% LA (AM/LA20, M_n = 19 → 9 kDa) after disulfide reduction. Thermogravimetric analysis also indicated faster thermal degradation of AM/LA due to the incorporation of weaker S-S and S-C linkages. Increasing LA content reduced hydrophilicity, and the copolymers were treated with NaOH to ensure water solubility. However, at 700 ppm, poly(AM) homopolymer reduced methane consumption during hydrate growth to 54% with respect to the uninhibited system, while gas consumption for the carboxylate AM/LA20 reached 78%. An advantageous feature of LA is its carboxylic acid, allowing desired functionalities to be grafted onto the degradable copolymer. Isopropyl amine (IPAm) was coupled with LA to form an amide known to be effective during hydrate inhibition (LA(IPAm)). The copolymer AM/LA(IPAm)20 demonstrated better water solubility compared to the original AM/LA20. Furthermore, the desirable IPAm functionality allowed the hydrate inhibition to be re-established at 54%, nearly recovering the performance of the poly(AM) homopolymer. This article assesses the application of LA and LA derivatives as building blocks for degradable amide-based kinetic hydrate inhibitors by validating their degradability with material characterizations and their inhibition performance during structure I hydrate growth. Full article

Aqueous semolina suspensions were reacted with spherical gold nanoparticles (AuNPs, nominal diameter, 20 nm) to assess the accessibility of cysteine thiols in durum wheat proteins, focusing on network-forming gluten proteins. Unlike small thiol reagents, covalent bond formation between gold ions on the AuNPs surface and protein thiols was greatly facilitated by the addition of 1% sodium dodecyl sulfate (SDS). SDS weakens non-covalent hydrophobic interactions within and among proteins, increasing the exposure of buried thiols without altering disulfide bonds. MS/MS analysis of proteolytic fragments from the isolated AuNP-protein covalent complexes allowed identification of the bound proteins. Proteomics data suggests that AuNPs also associate with gluten proteins lacking free thiols in their native structure, which are bound to AuNPs by forming disulfide bonds with other gluten proteins containing accessible thiols, via thiol-disulfide exchange reactions. This implies that thiol-disulfide reshuffling among gluten proteins occurs already in the grain, enabling proteins without free thiols to become part of AuNP-bound assemblies and revealing specific protein species involved in these early interactions. These observations highlight the role of thiol–disulfide exchange within the grain matrix, elucidating how such molecular rearrangements influence the topology and strength of protein networks in food and in related biopolymeric systems. Results of this exploratory study are discussed for their molecular relevance and for the potential use of size-based analytical and structural approaches in other biological contexts. Full article

2-methylisoborneol (MIB, d = 0.6 nm) and dimethyl disulfide (DMDS, d = 0.7 nm) produced by algal metabolism are the main olfactory contaminants of drinking water. Activated carbon (AC) adsorption is an effective method to remove MIB/DMDS, yet critical gaps remain regarding the dominant factors and mechanisms governing their different adsorption performance. The microporous filling mechanism is the dominant mechanism for the adsorption of MIB and DMDS by AC. Surface functional groups play a supporting role in the adsorption process by modulating the hydrophilicity/hydrophobicity of the carbon surface. This study systematically evaluated the adsorption performance of three ACs—coconut shell-derived (CSC), coal-based (CAC), and Sargassum-derived (SAC)—for MIB and DMDS removal. Comparative analysis revealed the superior adsorption performance of CSC, achieving 87.41% removal of MIB and 71.2% removal of DMDS at 20 mg/L. Both MIB and DMDS adsorption adhere to the Langmuir isotherm, indicating monolayer coverage with uniform energy. Kinetic studies demonstrated that the PSO model fits the MIB adsorption process best, while the PFO model fits the DMDS adsorption process best. The FTIR confirmed physical adsorption, with no new chemical bonds formed. Furthermore, regenerated CSC retains significant adsorption capacities, achieving 85.89% and 68.49% of the original capacity for MIB and DMDS, respectively, after five regeneration cycles. This research provides fundamental insights into the mechanistic role of AC properties in odorant removal processes, supporting its sustainable application in water treatment. Full article