Search Results (91)

Growing demand for low-sodium surimi products has driven the search for safe salt alternatives. Anionic peptides (APPs) and cationic peptides (CPPs) were isolated from sheepskin collagen via Diethylaminoethyl (DEAE) chromatography. CPPs contained higher arginine (46.11%) and lysine (4.64%) than APPs (40.57% and 3.99%, respectively), while APPs were enriched in acidic amino acids like glutamic acid (3.88%). Comprehensive evaluations of low-salt silver carp surimi gels showed both peptides significantly improved gel strength and water-holding capacity (WHC). The water-holding capacity increased from 60.68% in the blank control group to 74.31% in the CPP-treated group, while that in the APP-treated group was 66.86%. Cooking loss was significantly reduced, decreasing from 40.64% in the blank control group to 28.57% in the CPP-treated group and 34.52% in the APP-treated group. The samples achieved a quality comparable to that of the NaCl-supplemented group, with CPP outperforming APP in terms of hardness and gel network density. The LF-NMR confirmed enhanced water retention by reducing free water (T₂₂) and increasing bound water (T₂b). The FTIR indicated a conformational shift from α-helix to β-sheet, and the SEM revealed denser networks with fewer large voids. The SDS-PAGE demonstrated enhanced myosin heavy chain (MHC) cross-linking, more pronounced in the CPP-treated samples. CPPs exerted stronger electrostatic attraction with negatively charged surimi proteins (isoelectric point 5.5), while APPs chelated Ca²⁺ to activate transglutaminase. These findings validate APPs and CPPs as promising salt substitutes, enabling low-sodium surimi production and high-value utilization of sheepskin by-products. Full article

This study evaluated the bioactive potential of Thai silkworms (Bombyx mori) at three developmental stages—mature silkworm (MS), A-silking silkworm (AS), and pupae (PP)—as alternative protein sources for functional hydrolysates. Silkworm powders were hydrolyzed with Alcalase^® (5% w/w, 1 h, 60 °C) to obtain MS hydrolysate powder (MSHP), AS hydrolysate powder (ASHP), and PP hydrolysate powder (PPHP). AS contained the highest protein content (72.13%), followed by MS (70.20%) and PP (56.70%). Amino acid profiling revealed stage-specific and hydrolysis-dependent variations, MS was enriched in phenylalanine and histidine, AS in threonine, valine, and tyrosine, and PP in lysine, leucine, and arginine. Hydrolysates showed markedly increased amino acid levels across all samples, indicating enhanced peptide release and improved nutritional quality. The hydrolysates achieved yields of 61–64% and protein recoveries of approximately 46%. MSHP and ASHP exhibited higher degrees of hydrolysis than PPHP. Among the biological activities, MSHP demonstrated the strongest angiotensin-converting enzyme (ACE) inhibition (88.46%), whereas PPHP exhibited the greatest antioxidant capacity (DPPH, ABTS, FRAP). Overall, Alcalase^® hydrolysis effectively enhanced silkworm bioactivity, supporting their potential as multifunctional ingredients for functional foods and nutraceuticals targeting cardiovascular and oxidative stress-related disorders. Full article

Lysine methylation is a critical post-translational modification catalyzed by lysine methyltransferases (KMTs), originally characterized in the regulation of histones. However, the breadth of non-histone targets remains largely unexplored. Here, we used a systematic peptide array-based approach to define a substrate preference motif for the SET-domain-containing KMT MLL4 (KMT2D), a member of the COMPASS complex and a known H3K4 methyltransferase. Using this motif, we identified CXXC finger protein 1 (CFP1), a core component of Setd1A/B complexes, as a putative MLL4 substrate. In vitro methyltransferase assays confirmed robust methylation of CFP1 by an MLL4-WRAD complex. Surprisingly, while initial predictions implicated K328, array-based methylation profiling revealed multiple lysine residues within CFP1’s lysine-rich basic domain as methylation targets, including K331, K335, K339, and K340. We further demonstrated that CFP1 methylation likely modulates its interaction with MLL4’s PHD cassettes and facilitates binding to Setd1A. Binding preferences of MLL4’s PHD1–3 and PHD4–6 domains varied with methylation state and site, suggesting non-histone methyl mark recognition by these cassettes. Pulldown assays confirmed that methylated, but not unmethylated, CFP1 binds Setd1A, supporting a potential methyl-switch mechanism. Together, our findings propose CFP1 as a potential non-histone substrate of MLL4 and suggest that MLL4 may regulate Setd1A/B function indirectly via CFP1 methylation. This study expands the substrate landscape of MLL4 and lays the groundwork for future investigations into non-histone methylation signaling in chromatin regulation. Full article

The SETD6 protein lysine methyltransferase monomethylates specific lysine residues in a diverse set of substrates which contain the target lysine residue in a highly variable amino acid sequence context. To investigate the mechanism underlying this multispecificity, we analyzed SETD6 substrate recognition using AlphaFold 3 docking and peptide SPOT array methylation experiments. Structural modeling of the SETD6–E2F1 complex suggested that substrate binding alone is insufficient to restrict SETD6 activity to only one lysine residue, pointing to additional sequence readout at the target site. Methylation of mutational scanning peptide SPOT arrays derived from four different SETD6 substrates (E2F1 K117, H2A.Z K7, RELA K310, and H4 K12) revealed sequence preferences of SETD6 at positions −1, +2, and +3 relative to the target lysine. Notably, glycine or large aliphatic residues were favored at −1, isoleucine/valine at +2, and lysine at +3. These preferences, however, were sequence context dependent and variably exploited among different substrates, indicating conformational variability of the enzyme–substrate interface. Mutation of SETD6 residue L260, which forms a contact with the +2 site in the available SETD6-RELA structure, further demonstrated substrate-specific differences in recognition at the +2/+3 sites. Together, these findings reveal a versatile mode of peptide recognition in which the readout of each substrate position depends on the overall substrate peptide sequence. These findings can explain the multispecificity of SETD6 and similar mechanisms may underlie substrate selection in other protein methyltransferases. Full article

Background: Histone post-translational modifications (PTMs) play a pivotal role in the regulation of chromatin structure and gene expression, making them key targets in structural and epigenetic research. Synthetic histone peptides bearing specific PTMs are essential tools for elucidating the molecular mechanisms of histone function and protein–histone interactions. Methods: We synthesized histone H4 tail peptides containing site-specific lysine modifications using solid-phase peptide synthesis (SPPS). The correct synthesis of the peptides was confirmed by their molecular weights using a mass spectrometer. Results: An improved high-performance liquid chromatography (HPLC) method was developed to efficiently separate peptides with one modification difference. In alignment with green chemistry principles, we evaluated ethanol and isopropanol as an alternative organic solvent to acetonitrile in the mobile phase. The optimized HPLC method using acetonitrile enabled effective resolution of closely related peptide species, providing peptides suitable for downstream applications requiring high purities such as structural biology. Conclusions: This study presents a strategy for the purification of histone PTM peptides, emphasizing both analytical performance and sustainability. Further investigation must be undergone to develop high-precision purification using green chemicals. Full article

Given the limited knowledge of the effect of post-translational modifications (PTMs) on protein structure, in this study we investigated whether introducing one-to-three RA-related PTMs into the α-fibrin (617–631) peptide influences the conformation and structure of the peptide antigen that could be responsible for the autoantibody recognition. Ten peptides containing a different number of PTMs within their primary structure were synthesized and their recognition by sera from RA patients was analyzed. The conformation of the peptides was studied by circular dichroism (CD) and the structure of the most relevant antigenic peptides was determined by nuclear magnetic resonance (NMR) and enhanced-sampling molecular dynamics (MD). Although peptides containing citrulline (Cit) showed a higher degree of binding to AMPAs than peptides containing only homocitrulline and/or acetyl-lysine, the latter were able to bind to AMPAs in sera that showed a small response to peptides with Cit, with the response being different depending on the position of each PTM. CD and NMR analyses indicated a series of half-turn conformations in the Lys620-Arg630 region. MD simulations generated a set of conformations compatible with the NMR NOEs. The effect of the PTMs was observed in intra-molecular contacts, hydrogen bonds and van der Waals interactions, generating more collapsed conformations. Differences in autoantibody reactivity between peptides bearing different PTMs within their primary structures are noted. Peptides with PTMs adopt different conformations than unmodified peptides, probably due to the lower net charge of peptides with multiple PTMs, which may explain their recognition by autoantibodies. Full article

The growing demand for sustainable protein sources has boosted interest in Andean pseudocereals, particularly quinoa (Chenopodium quinoa), cañihua (Chenopodium pallidicaule), and kiwicha (Amaranthus caudatus), due to their complete nutritional profile, high digestibility, and low allergenic potential. Their inclusion in vegetarian and vegan diets represents a viable alternative that can replace animal proteins without compromising on nutritional quality. This study presents a critical review of indexed scientific literature analyzing essential amino acid composition, protein quality values—such as PDCAAS (Protein Digestibility-Corrected Amino Acid Score) and DIAAS (Digestible Indispensable Amino Acid Score)—and the impact of various processing technologies on the functionality of Andean proteins. Results show that these grains contain between 13 and 18 g of protein per 100 g of dry product and provide adequate levels of lysine, methionine, and threonine, meeting FAO (Food and Agriculture Organization) requirements for adult nutrition. Processes such as germination, fermentation, enzymatic hydrolysis, and extrusion have demonstrated improvements in both amino acid bioavailability and functional properties of proteins, enabling their application in gluten-free breads, meat analogs, and functional beverages. Furthermore, emerging strategies such as nanotechnology, bioactive peptide generation, and gene editing via CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats)—a precise genome editing tool—open new possibilities for enhancing the nutritional and functional value of pseudocereals in the food industry. Taken together, the findings consolidate the strategic role of Andean grains as key ingredients in the development of sustainable, functional, and plant-based foods. Full article

We report herein the development of a polyclonal antibody against ochratoxin A (OTA) using a specially designed synthetic OTA derivative as the immunizing hapten. This OTA derivative contains a tetrapeptide linker (glycyl-glycyl-glycyl-lysine, GGGK), through which it can be linked to a carrier protein and form an immunogenic conjugate. The OTA derivative (OTA-glycyl-glycyl-glycyl-lysine, OTA-GGGK) has been synthesized on a commercially available resin via the well-established Fmoc-based solid-phase peptide synthesis (Fmoc-SPPS) strategy; overall, this approach has allowed us to avoid tedious liquid-phase synthesis protocols, which are often characterized by multiple steps, several intermediate products and low overall yield. Subsequently, OTA-GGGK was conjugated to bovine thyroglobulin through glutaraldehyde, and the conjugate was used in an immunization protocol. The antiserum obtained was evaluated with a simple-format ELISA in terms of its titer and capability of recognizing the natural free hapten; the anti-OTA antibody, as a whole IgG fragment, was successfully applied to three different immunoanalytical systems for determining OTA in various food materials and wine samples, i.e., a multi-mycotoxin microarray bio-platform, an optical immunosensor, and a biotin–streptavidin ELISA, which has proved the analytical effectiveness and versatility of the anti-OTA antibody developed. The same approach may be followed for developing antibodies against other low-molecular-weight toxins and hazardous substances. Full article

The application of high-performance liquid chromatography with tandem mass spectrometry (HPLC-MS/MS) in the analysis of peptide therapeutics demonstrates its capacity to achieve high sensitivity and selectivity, which are essential qualities for the expanding peptide therapeutic industry. Given the challenges posed by hydrophilic peptides in reversed-phase chromatography, we investigated the necessity of a derivatization procedure to improve chromatographic separation and quasimolecular ion fragmentation during MS/MS detection. We investigated how eight different derivatizing agents react with a hydrophilic lysine- and arginine-containing human ezrin peptide-1 (HEP-1) to identify the most suitable one. The results showed that the reaction of HEP-1 with propionic anhydride proceeds most rapidly and completely, providing a high and reproducible yield of the product, which has sufficient retention on the RP column. The 4-propionylated derivative of HEP-1, compared to the other derivatives considered, demonstrates the most pronounced MS/MS fragmentation. The retention time of 2.42 min allows the separation of the substance from the interfering components of the blood plasma matrix and provides a limit of quantification of 5.00 ng/mL, which allows the use of this derivatizing agent for subsequent applications in pharmacokinetic studies, and this approach can improve the analytical parameters of similar peptides in other HPLC-MS/MS studies. Full article

This study investigated the potential neuroprotective mechanisms of porcine brain enzyme hydrolysate (PBEH) against Alzheimer’s disease pathology using differentiated SH-SY5Y cells. Differentiated neuronal cells were treated with 40 μM amyloid-β(1-42; Aβ) to induce neurotoxicity, followed by PBEH treatment (12.5–400 μg/mL), Com-A (peptide-based neuroprotective supplement; 200 μg/mL) treatment, and Com-B (herbal extract known for improving memory function; 100 μg/mL) treatment. Key assessments included cell viability, Aβ aggregation in adding 10 μM Aβ, amyloidogenic proteins (APP, BACE), synaptic markers (BDNF, ERK), apoptotic markers (BAX/BCL-2, caspase-3), oxidative stress (reactive oxygen species (ROS)), cholinergic function (ChAT, AChE), MAPK signaling (JNK, p38), and neuroinflammation (IL-1β). PBEH contained high concentrations of amino acids, including L-lysine (32.3 mg/g), L-leucine (42.4 mg/g), L-phenylalanine (30.0 mg/g) and the PSIS peptide (86.9 μg/g). Treatment up to 400 μg/mL showed no cytotoxicity and had cognitive protection effects up to 152% under Aβ stress (p < 0.05). PBEH significantly attenuated Aβ aggregation, decreased APP (28%) and BACE (51%) expression, enhanced synaptic function through increased BDNF, and restored ERK phosphorylation (p < 0.05). Anti-apoptotic effects included a 76% reduction in the BAX/BCL-2 ratio, a 47% decrease in caspase-3, and a 56% reduction in ROS levels. Cholinergic function showed restoration via increased ChAT activity (p < 0.01) and decreased AChE activity (p < 0.05). PBEH reduced IL-1β levels by 70% and suppressed JNK/p38 phosphorylation (p < 0.05). While Com-A enhanced BDNF and Com-B showed anti-inflammatory effects, PBEH demonstrated activity across multiple pathway markers. In conclusion, these findings suggest that PBEH may enable neuronal preservation through multi-pathway modulation, establishing foundational evidence for further mechanistic investigation in cognitive enhancement applications. Full article

Alzheimer’s disease (AD), a predominant neurodegenerative disorder, is clinically characterized by progressive cognitive deterioration and behavioral deficits. An in-depth understanding of the pathogenesis and neuropathology of AD is essential for the development of effective treatments and early diagnosis techniques. The neuropathological signature of AD involves two hallmark lesions: intraneuronal neurofibrillary tangles composed of hyperphosphorylated tau aggregates and extracellular senile plaques containing amyloid-β (Aβ) peptide depositions. Although Aβ-centric research has dominated AD investigations over the past three decades, pharmacological interventions targeting Aβ pathology have failed to demonstrate clinical efficacy. Tau, a microtubule-associated protein predominantly localized to neuronal axons, orchestrates microtubule stabilization and axonal transport through dynamic tubulin interactions under physiological conditions. In AD pathogenesis, however, tau undergoes pathogenic post-translational modifications (PTMs), encompassing hyperphosphorylation, lysine acetylation, methylation, ubiquitination, and glycosylation. These PTM-driven alterations induce microtubule network disintegration, mitochondrial dysfunction, synaptic impairment, and neuroinflammatory cascades, ultimately culminating in irreversible neurodegeneration and progressive cognitive decline. This review synthesizes contemporary advances in tau PTM research and delineates their mechanistic contributions to AD pathogenesis, thereby establishing a framework for biomarker discovery, targeted therapeutic development, and precision medicine approaches in tauopathies. This review synthesizes contemporary advances in tau PTM research and delineates their mechanistic contributions to AD pathogenesis, thereby establishing a solid theoretical and experimental basis for the early diagnosis of neurodegenerative diseases, the discovery of therapeutic targets, and the development of novel therapeutic strategies. Full article

Microalgae have emerged as a sustainable and efficient source of protein, offering a promising alternative to conventional animal and plant-based proteins. Species such as Arthrospira platensis and Chlorella vulgaris contain protein levels ranging from 50% to 70% of their dry weight, along with a well-balanced amino acid profile rich in essential amino acids such as lysine and leucine. Their cultivation avoids competition for arable land, aligning with global sustainability goals. However, the efficient extraction of proteins is challenged by their rigid cell walls, necessitating the development of optimized methods such as bead milling, ultrasonication, enzymatic treatments, and pulsed electric fields. These techniques preserve functionality while achieving yields of up to 96%. Nutritional analyses reveal species-dependent digestibility, ranging from 70 to 90%, with Spirulina platensis achieving the highest rates due to low cellulose content. Functionally, microalgal proteins exhibit emulsifying, water-holding, and gel-forming properties, enabling applications in baking, dairy, and meat analogs. Bioactive peptides derived from these proteins exhibit antioxidant, antimicrobial (inhibiting E. coli and S. aureus), anti-inflammatory (reducing TNF-α and IL-6), and antiviral activities (e.g., Dengue virus inhibition). Despite their potential, commercialization faces challenges, including regulatory heterogeneity, high production costs, and consumer acceptance barriers linked to eating habits or sensory attributes. Current market products like Spirulina-enriched snacks and Chlorella tablets highlight progress, but food safety standards and scalable cost-effective extraction technologies remain critical for broader adoption. This review underscores microalgae’s dual role as a nutritional powerhouse and a source of multifunctional bioactives, positioning them at the forefront of sustainable food and pharmaceutical innovation. Full article

Royal jelly and medical grade honey are traditionally used in treating wounds and infections, although their effectiveness is often variable and insufficient. To overcome their limitations, we created novel amphiphiles by modifying the main reparative and antimicrobial components, queen bee acid (hda) and 10-hydroxyl-decanoic acid (hdaa), through peptide bonding with specific tripeptides. Our molecular design incorporated amphiphile targets as being biocompatible in wound healing, biodegradable, non-toxic, hydrogelable, prohealing, and antimicrobial. The amphiphilic molecules were designed in a hda(hdaa)-aa1-aa2-aa3 structural model with rational selection criteria for each moiety, prepared via Rink/Fmoc-tBu-based solid-phase peptide synthesis, and structurally verified by NMR and LC–MS/MS. We tested several amphiphiles among those containing moieties of hda or hdaa and isoleucine–leucine–aspartate (ILD-amidated) or IL-lysine (ILK-NH₂). These tests were conducted to evaluate their prohealing and antimicrobial hydrogel properties. Our observation of their hydrogelation and hydrogel-rheology showed that they can form hydrogels with stable elastic moduli and injectable shear-thinning properties, which are suitable for cell and tissue repair and regeneration. Our disc-diffusion assay demonstrated that hdaa-ILK-NH₂ markedly inhibited Staphylococcus aureus. Future research is needed to comprehensively evaluate the prohealing and antimicrobial properties of these novel molecules modified from hda and hdaa with tripeptides. Full article

The Maillard reaction (MR) between sugars and amino acids, peptides, or proteins is understood to occur gradually during the production and aging of sparkling wines, where it contributes to caramel, roasted, and toasted aromas. Divalent metal ions can accelerate the MR, although this has not been previously reported in wine or wine-like conditions. In this work, the effect of calcium (Ca) and magnesium (Mg) ions on the concentration of 10 Maillard reaction-associated products (MRPs) was measured in modified sparkling base wine during accelerated aging at 50 °C for four weeks. Chardonnay base wine was modified by the addition of fructose (0.02 M) and a single amino acid (lysine, glycine, cysteine; 0.01 M) in combination with Ca²⁺ or Mg²⁺ at zero, low (10 mg/L), or high (50 mg/L) dose levels. MRPs were quantified by headspace solid-phase microextraction coupled with gas chromatography–mass spectrometry (HS-SPME-GC/MS), sugar concentration was measured by enzymatic assay, and amino acids and free metal ions were monitored by capillary electrophoresis. Fructose levels did not substantially decrease during aging despite increases in all MRPs, suggesting that trace sugars or α-dicarbonyl species present in the wine matrix likely play a greater role in MRP formation than fructose. Aging duration and amino acid content had a greater effect than metal addition on the composition of the MRPs. Treatments containing cysteine and 50 mg/L Ca²⁺ had elevated concentrations of benzaldehyde and furfural ethyl ether following 4 weeks of accelerated aging. This work identified key MRPs that increase during base wine accelerated aging and informs future research on the relationship between wine composition and aging markers. Full article

Selenium reagents are useful for selenoenzyme-mimicking reactions, as well as for organic synthesis. However, the reaction waste containing selenium frequently smells unpleasant and exhibits serious toxicity. Herein, we have developed new-type on-resin selenium reagents, H-UXX···-PAM (5) and Ac-(X)U*XX···-PAM (6), where U and U* represent selenocysteine (U) and p-methoxybenzyl (PMB)-protected U, respectively, as recyclable catalysts, in which U-containing peptide chains are linked to the polystyrene resin PAM. Synthesized on-resin selenopeptides 5a–g with a variable amino acid sequence were evaluated for their glutathione peroxidase (GPx)-like activity using the UV and ¹H NMR methods, using the reaction between dithiothreitol (DTT^red) and H₂O₂ in methanol. It was found that the intramolecular interaction between U and a basic amino acid residue, such as histidine (H) and lysine (K), enhances peroxidase activity through the formation of an NH···Se hydrogen bond. On the other hand, the catalytic activity of 6a–d was evaluated in the oxidative cyclization of β,γ-unsaturated acids (7) into α,β-unsaturated lactones (8). Although the yield of 8 was significantly decreased after second- or third-round reaction, due to detachment of the selenium moiety from the resin, the results demonstrated reusability, as well as a substrate scope of 6 as a catalyst. Since U is a natural amino acid, on-resin selenopeptides are potential targets as novel-type green redox catalysts. Full article