Search Results (6,246)

Glutaminyl-peptide cyclotransferases (QCs) convert the N-terminal glutamine or glutamate residues of protein and peptide substrates into pyroglutamate (pE) by releasing ammonia or a water molecule. The N-terminal pE modification protects peptides/proteins against proteolytic degradation by amino- or exopeptidases, increasing their stability. Mammalian QC is abundant in the brain and a large amount of evidence indicates that pE peptides are involved in the onset of neural human pathologies such as Alzheimer’s and Huntington’s disease and synucleinopathies. Hence, human QC (hQC) has become an intensively studied target for drug development against these diseases. Soon after its characterization, hQC was identified as a Zn-dependent enzyme, but a partial restoration of the enzyme activity in the presence of the Co(II) ion was also reported, suggesting a possible role of this metal ion in catalysis. The present work aims to investigate the structure of demetallated hQC and of the reconstituted enzyme with Zn(II) and Co(II) and their behavior in the presence of known inhibitors. Furthermore, our structural determinations provide a possible explanation for the presence of the mononuclear metal binding site of hQC, despite the presence of the same conserved metal binding motifs present in distantly related dinuclear aminopeptidase enzymes. Full article

The H9N2 subtype of avian influenza virus (AIV) causes enormous economic losses and poses a significant threat to public health; the development of vaccines against avian influenza is ongoing. To study the immunogenicity of hemagglutinin (HA) protein, we constructed a recombinant pET-32a-HA plasmid, induced HA protein expression with isopropyl β-D-1-thiogalactopyranoside (IPTG), verified it by SDS–PAGE and Western blotting, and determined the sensitivity of the recombinant protein to acid and heat. Subsequently, mice were immunized with the purified HA protein, and the immunization effect was evaluated according to the hemagglutination inhibition (HI) titer, serum IgG antibody titer, and cytokine secretion level of the mice. The results showed that the molecular weight of the HA protein was approximately 84 kDa, and the protein existed in both soluble and insoluble forms; in addition, the HA protein exhibited good acid and thermal stability, the HI antibody titer reached 6 log2–8 log2, and the IgG-binding antibody titer was 1:1,000,000. Moreover, the levels of IL-2, IL-4, and IL-5 in the immunized mouse spleen cells were significantly increased compared with those in the control group. However, the levels of IL-1β, IL-6, IL-13, IFN-γ, IL-18, TNF-α, and GM-CSF were decreased in the immunized group. The recombinant HA protein utilized in this study exhibited good stability and exerted beneficial immune effects, providing a theoretical basis for further research on influenza vaccines. Full article

A microwave technique was used to prepare a superabsorbent polymer (SAP) by grafting two hydrophilic monomers onto a polysaccharide substrate. The monomers used were acrylic acid (AA) or acrylamide (AM) and were grafted onto a pullulan (PUL) substrate to form PUL-g-AA (SAP₁) and PUL-g-AM (SAP₂), respectively. The monomers (AM/AA) were grafted together onto a PUL substrate to form PUL-g-(AM/AA) (SAP₃). Grafting parameters such as grafting efficiency with the percentage, the conversion of monomer into polymer, gel content, water retention, water adsorption capacity, and swelling kinetics were determined. Additionally, the effect of environmental pH (2, 4, 7, 9, and 12) and sodium dodecylbenzene sulfonate (SDBS) surfactant was evaluated, where 1, 2, 3, 4, and 5 mM of SDBS was added to form SAP₄ to SAP₈. The FTIR results show that AM was grafted onto PUL through an aliphatic C-N bond, while AA grafting occurred through a single C-C bond. The grafting efficiency with AM was higher than with AA, as well as showing a superior gel content. Water absorbance capacity and water retention increased with the grafting of AA and AM together for SAP₃. The highest absorbent capacity, water retention, gel content, and grafting parameters values were obtained with a 3 mM SDBS content and a pH of 7. The swelling kinetics showed that the increases in the theoretical and experimental swelling equilibriums were 72% and 82%, respectively, for SAP₆ compared to the values of these parameters for SAP_3. The water absorption capacity of the hydrogel increases upon increasing the pH to 7 and then gradually decreases. XRD demonstrated the improved crystallinity and crystalline size of the hydrogel after grafting polymerization of AM/AA onto PUL, in addition to enhanced thermal stability. On the contrary, FE-SEM demonstrated that SDBS improves the porosity and pore size of the hydrogel surface with SAP₆. Full article

Albendazole (ABZ) is a highly effective yet poorly water-soluble antiparasitic drug known to form salts (ABZ-FMA, ABZ-DTA, and ABZ-HCl) with fumaric acid (FMA), D-tartaric acid (DTA), and hydrochloric acid (HCl). This research utilized a range of analytical techniques, including Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance hydrogen spectroscopy (¹H NMR), powder X-ray diffraction (PXRD), dynamic vapor sorption (DVS), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM), to validate and characterize the solid-state properties of these drug salts. This study also assessed the solubility and intrinsic dissolution rate (IDR) of these salts under different pH conditions compared to the active pharmaceutical ingredient (API) and conducted stability studies. Moreover, the in vivo pharmacokinetic performance of ABZ salt was evaluated. The results of this study reveal that the new solid form of ABZ is primarily associated with amino acid esters and benzimidazole groups, forming intermolecular interactions. All three ABZ salts significantly improved the solubility and dissolution rate of ABZ, with ABZ-HCl demonstrating the optimal performance. Importantly, the drug salt exhibited robust physical stability when exposed to adverse conditions, including strong light irradiation (4500 ± 500 lux), high humidity (92.5 ± 5% relative humidity), elevated temperatures (50 ± 2 °C), and accelerated test conditions (40 °C/75 ± 5% relative humidity). Lastly, the in vivo pharmacokinetic analysis demonstrated that ABZ salt led to a substantial increase in AUC_(0–24) and C_max compared to ABZ. This elevation in solubility in aqueous solvents signifies that ABZ salt exhibits characteristics that can enhance oral bioavailability and pharmacokinetics. These findings provide potential solutions for the development of more effective and innovative drug formulations. Full article

This study investigates the crosslinking dynamics and swelling properties of pH-responsive poly(ethylene glycol) (PEG)/poly(acrylic acid) (PAA) interpenetrating polymer network (IPN) hydrogels. These hydrogels feature denser crosslinked networks compared to PEG single network (SN) hydrogels. Fabrication involved a two-step UV curing process: First, forming PEG-SN hydrogels using poly(ethylene glycol) diacrylate (PEGDA) through UV-induced free radical polymerization and crosslinking reactions, then immersing them in PAA solutions with two different molar ratios of acrylic acid (AA) monomer and poly(ethylene glycol) dimethacrylate (PEGDMA) crosslinker. A subsequent UV curing step created PAA networks within the pre-fabricated PEG hydrogels. The incorporation of AA with ionizable functional groups imparted pH sensitivity to the hydrogels, allowing the swelling ratio to respond to environmental pH changes. Rheological analysis showed that PEG/PAA IPN hydrogels had a higher storage modulus (G′) than PEG-SN hydrogels, with PEG/PAA-IPN5 exhibiting the highest modulus. Thermal analysis via thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) indicated increased thermal stability for PEG/PAA-IPN5 compared to PEG/PAA-IPN1, due to higher crosslinking density from increased PEGDMA content. Consistent with the storage modulus trend, PEG/PAA-IPN hydrogels demonstrated superior mechanical properties compared to PEG-SN hydrogels. The tighter network structure led to reduced water uptake and a higher gel modulus in swollen IPN hydrogels, attributed to the increased density of active network strands. Below the pK_a (4.3) of acrylic acid, hydrogen bonds between PEG and PAA chains caused the IPN hydrogels to contract. Above the pKa, ionization of PAA chains induced electrostatic repulsion and osmotic forces, increasing water absorption. Adjusting the crosslinking density of the PAA network enabled fine-tuning of the IPN hydrogels’ properties, allowing comprehensive comparison of single network and IPN characteristics. Full article

To enhance the functional properties of walnut protein isolate (WalPI), hydrophilic whey protein isolate (WPI) was selected to formulate WalPI-WPI nanoparticles (nano-WalPI-WPI) via a pH cycling technique. These nano-WalPI-WPI particles were subsequently employed to stabilize high internal phase Pickering emulsions (HIPEs). By adjusting the mass ratio of WalPI to WPI from 9:1 to 1:1, the resultant nano-WalPI-WPI exhibited sizes ranging from 70.98 to 124.57 nm, with a polydispersity index of less than 0.326. When the mass ratio of WalPI to WPI was 7:3, there were significant enhancements in various functional properties: the solubility, denaturation peak temperature, emulsifying activity index, and emulsifying stability index increased by 6.09 times, 0.54 °C, 318.94 m²/g, and 552.95 min, respectively, and the surface hydrophobicity decreased by 59.23%, compared with that of WalPI nanoparticles (nano-WalPI), with the best overall performance. The nano-WalPI-WPI were held together by hydrophobic interactions, hydrogen bonding, and electrostatic forces, which preserved the intact primary structure and improved resistance to structural changes during the neutralization process. The HIPEs stabilized by nano-WalPI-WPI exhibited an average droplet size of less than 30 μm, with droplets uniformly dispersed and maintaining an intact spherical structure, demonstrating superior storage stability. All HIPEs exhibited pseudoplastic behavior with good thixotropic properties. This study provides a theoretical foundation for enhancing the functional properties of hydrophobic proteins and introduces a novel approach for constructing emulsion systems stabilized by composite proteins as emulsifiers. Full article

Phytoplankton plays a key role in the stabilization of aquatic ecosystems. However, there is a lack of research on the structure of phytoplankton communities and their influencing factors in shallow lakes in Southeast Hubei. In this study, four typical lakes were selected in the summer of 2019, and the phytoplankton community structure and its drivers were investigated for each lake. The results showed that the number of phytoplankton species, dominant species, biomass, and abundance varied among lakes. A comprehensive trophic level index (TLI) assessment showed that Lake Xiandao was oligotrophic, Lake Baoan was light eutrophic, and Lake Wang and Lake Ci were moderate eutrophic. The Shannon–Wiener, Margalef, and Pielou indices showed that the phytoplankton communities of Lake Wang and Lake Ci are less stable, and the water bodies are more severely contaminated. In contrast, the communities of the Lake Baoan and Lake Xiandao are more stable and have superior water quality. A redundancy analysis (RDA) indicated that the primary variables influencing phytoplankton community structures were pH and water temperature (WT) (Lake Ci); permanganate index (COD_Mn) and pH (Lake Xiandao); WT and total nitrogen (TN) (Lake Wang); and WT and total phosphorus (TP) (Lake Baoan). Full article

Photodynamic therapy (PDT) is an emerging treatment modality that utilizes light-sensitive compounds, known as photosensitizers, to produce reactive oxygen species (ROS) that can selectively destroy malignant or diseased tissues upon light activation. This study investigates the incorporation of two porphyrin structures, 5-(4-hydroxy-3-methoxyphenyl)-10,15,20-tris-(4-acetoxy-3-methoxyphenyl) porphyrin (P2.2.) and 5,10,15,20-tetrakis-(4-acetoxy-3-methoxyphenyl) porphyrin (P2.1.), into hydroxypropyl cellulose (HPC) hydrogels for potential use in topical photodynamic therapy (PDT). The structural and compositional properties of the resulting hydrogels were characterized using advanced techniques such as Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA), atomic force microscopy (AFM), UV-Visible (UV-Vis) spectroscopy, and fluorescence spectroscopy. FTIR spectra revealed a slight shift of the main characteristic absorption bands corresponding to the porphyrins and their interactions with the HPC matrix, indicating successful incorporation and potential hydrogen bonding. XRD patterns revealed the presence of crystalline domains within the HPC matrix, indicating partial crystallization of the porphyrins dispersed within the amorphous polymer structure. TGA results indicated enhanced thermal stability of the HPC–porphyrin gels compared to 10% HPC gel, with additional weight loss stages corresponding to the thermal degradation of the porphyrins. Rheological analysis showed that the gels exhibited pseudoplastic behavior and thixotropic properties, with minimal impact on the flow properties of HPC by P2.1., but notable changes in viscosity and shear stress with P2.2. incorporation, indicating structural modifications. AFM imaging revealed a homogeneous distribution of porphyrins, and UV-Vis and fluorescence spectroscopy confirmed the retention of their photophysical properties. Pharmacotechnical evaluations showed that the hydrogels possessed suitable mechanical properties, optimal pH, high swelling ratios, and excellent spreadability, making them ideal for topical application. These findings suggest that the porphyrin-incorporated HPC hydrogels have significant potential as effective therapeutic agents for topical applications. Full article

Cheese whey (CW), a byproduct resulting from dairy processing, requires proper treatment and disposal. The use of microalgae during tertiary treatment emerges as a promising option due to its efficiency to remove chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP) from effluents obtained after secondary treatment processes. The present study was focused on treating CW effluent at two organic loads (C₁ and C₂—with different concentrations of COD, TN, and TP) (550–2200 mg·L⁻¹ of COD, 14–56 mg·L⁻¹ of TN, and 4.5–18 mg·L⁻¹ of TP) using the microalga Tetradesmus obliquus alone (C_M1 and C_M2) and in a consortium with the fungus Cuninghamella echinulata (C_MF1 and C_MF2), evaluating the residual values of COD, TN, and TP and removal efficiency. The experiments were carried out in an open system with a volumetric replacement ratio (VRR) of 40 and 60%. The C_M treatment showed residual values of COD in the range of 190–410 mg·L⁻¹ (removal efficiency: 57–68%), TN in the range of 6–24 mg·L⁻¹ (removal efficiency: 29–35%), and TP in the range of 0.90–3.0 mg·L⁻¹ (removal efficiency: 65–68%), after 7 days of volumetric replacement time (VRT) in a semicontinuous mode. In contrast, the consortium (C_MF) showed greater stability and efficiency in contaminant removal compared to the treatment system containing only the microalga, showing residual values of COD in the range of 61–226 mg·L⁻¹ (removal efficiency: 75–77%), TN in the range of 1.8–9.5 mg·L⁻¹ (removal efficiency: 70–74%), and TP in the range of 0.6–3.5 mg·L⁻¹ (removal efficiency: 66–70%), applying a lower VRT of 3 days and reaching the legislation standard for discharge to C_MF1 (VRR: 40 and 60%) and C_MF2 (VRR: 40%). The cell dry weight of 290–850 mg·L⁻¹ was obtained (microalga and microalga–fungus cultivation), which can be a valuable biomass for biotechnological applications. Finally, during microalga–fungus co-cultivation, there was greater system buffering (with less pH variation), ensuring a better system stability. Full article

This study aimed to assess the impact of Chlorella vulgaris supplementation in broilers’ diet, alone or in combination with vitamin E, on meat quality parameters, nutritional value, and oxidative stability during storage time. An experiment was conducted on 180 COBB 500 broiler chickens (14 days old), assigned into six treatments, following a 2 × 3 factorial arrangement. A corn–soybean meal diet was supplemented with three levels of C. vulgaris (0% in group C1, 1% in E1, 2% in E2), two levels of vitamin E (0% in C1, 250 ppm in C2), and a combination of them (1% C. vulgaris + 250 ppm vitamin (E3), 2% C. vulgaris + 250 ppm vitamin (E4)). Dietary incorporation of C. vulgaris, including those supplemented with vitamin E, resulted in a significant increase in meat protein content. DPA and DHA levels increased by 2.01-fold and 1.60-fold in the 2% C. vulgaris + vitamin E group. The PUFA/SFA ratio was increased across all dietary treatments (p < 0.0001). HPI and h/H registered the highest values as a result of 2% C. vulgaris supplementation, being linked with a positive effect in lowering cholesterol levels. Supplementation with 2% C. vulgaris and vitamin E exhibited a 1.45-fold increase in vitamin E concentration in thigh meat compared to the control group, being the highest level registered in thigh meat in this experiment. Metmyoglobin concentrations registered lower values in the thigh meat of the experimental groups, while deoxymyoglobin increased in the same groups when compared to the control group. The inclusion of C. vulgaris (1% and 2%) in combination with vitamin E (250 mg/kg) in broiler diets exhibited the best prevention of lipid oxidation after 7 days of refrigerated storage, defined by the highest efficiency factors assessed in terms of secondary oxidation products. Full article

Compared to other forms of drug administration, the use of Transdermal Drug Delivery Systems (TDDSs) offers significant advantages, including uniform drug release profiles that contribute to lower side effects and higher tolerability, avoidance of direct exposure to the gastrointestinal tract, better patient compliance due to their non-invasive means of application and others. Mesoporous silica membranes are of particular interest in this regard, due to their chemical stability and their tunable porous system, with adjustable pore sizes, pore volumes and surface chemistries. While this allows for fine-tuning and, thus, the development of optimized TDDSs with high loading capacities and the desired release profile of a given drug, its systemic availability also relies on skin penetration. In this paper, using a TDDS based on mesoporous silica membranes in Franz cell experiments on porcine skin, we demonstrate surprisingly substantial drug loss during skin penetration. Drug passage through porcine skin was found to be dependent on the age and pre-treatment of the skin. pH and temperature were major determinants of drug recovery rates as well, indicating drug loss in the skin by enzymatic metabolization. Regarding the TDDS, higher loading obtained by SO₃H surface modification of the mesoporous silica membranes reduced drug loss. Still, high loss rates in the skin were determined for different drugs, including anastrozole, xylazine and imiquimod. We conclude that, beyond the fine-tuned drug release profiles from the mesoporous silica membrane TDDS, remarkably high drug loss in the skin is a major issue for achieving desired skin penetration and, thus, the systemic availability of drugs. This also poses critical requirements for defining an optimal TDDS based on mesoporous silica membranes. Full article

Calcium-binding peptides have gained significant attention due to their potential applications in various fields. In this study, we aimed to prepare, characterize, and evaluate the stability of calcium-binding peptides derived from chicken blood. Chicken hemoglobin peptides (CPs) were obtained by protease hydrolysis and were applied to prepare chicken hemoglobin peptide–calcium chelate (CP-Ca). The preparation conditions were optimized, and the characteristics and stability of CP-Ca were analyzed. The optimal chelating conditions were determined by single-factor and response surface tests, and the maximum calcium ion chelating rate was 77.54%. Amino acid analysis indicated that glutamic acid and aspartic acid motifs played an important role in the chelation of the calcium ions and CP. According to the characterization analysis, CP-Ca was a different substance compared with CP; calcium ions chelated CPs via the sites of carbonyl oxygen, carboxyl oxygen, and amino nitrogen groups; and after the chelation, the structure changed from a smooth homogeneous plate to compact granular. The stability analysis showed that CP-Ca was stable at different temperatures, pH, and gastrointestinal conditions. The study indicates that chicken blood is a promising source of peptide–calcium chelates, providing a theoretical basis for application in functional foods and improving the utilization value of chicken blood. Full article

The increasing need for new treatments for obesity and diabetes has led to the development of new drugs and food supplements that could reduce carbohydrate absorption. Many starch blockers, based on common bean proteinaceous inhibitors against α-amylase (α-AI), are already present on the market. The extraction and purification of α-amylase inhibitor from a promising common bean cultivar from Sardinia (Nieddone) is described, highlighting the unique value of the Nieddone cultivar, particularly for its inhibitory activity on digestive enzymes and its complete lack of a hemagglutination effect on human red blood cells. The purification of α-AI involved two chromatographic steps (IEC and SEC) and was essential for revealing certain properties of the inhibitor. The purified inhibitor has a tetrameric structure (α₂β₂) and a molecular weight of approximately 42 kDa, as determined by SEC and SDS-PAGE, confirming it as a lectin-like inhibitor. The identification of the α-AI sequence was obtained by bottom-up high-resolution mass spectrometry, which allowed us to identify a unique peptide from the α chain and six unique peptides from the β chains. α-AI exhibited an optimum temperature of around 40 °C and two pH optima at 5 and 6.5, respectively. Its remarkable stability at high temperatures was measured (approximately 25% of activity retained even after 5 h at 100 °C), whereas the raw extract lost its activity entirely after just 10 min at 90 °C. Thus, the purification process significantly enhances the thermal stability of α-AI. The demonstrated effectiveness of the purified α-AI against the α-amylase enzyme in pigs, humans and insects underscores the protein’s potential for treating obesity and diabetes, as well as for managing insect pests. Full article

In this study, SEM, AFM, TEM, XPS, and electrochemical tests are used to study the passivation behavior of chromium alloyed high-strength rebar in simulated concrete pore (SCP) solutions with different pH values. The results show that after passivation in SCP solution with different pH values, the passivating film on the surface of the chromium alloyed rebar primarily consists of a layer of nanoscale oxide particles, which makes the passive film exhibit a p-n type semi-conductor, and the passive film presents a rhombohedral crystal structure. As the pH value of the SCP solution decreases, the nanoscale oxide particles on the surface of the rebar become denser, which leads to a reduction in the carrier density (N_q and N_a) of the passive film and an increase in film resistance (R₂) and charge transfer resistance (R₃), thus increasing the corrosion resistance of the passive film. The passive film on the surface of the chromium alloyed high-strength rebar predominantly exhibits a three-layer structure, the outer passive film layer is composed of Fe oxides, the stable layer of the passive film is composed of Fe oxides and Cr oxides, and the growth layer of inner passive film is composed of Cr oxides. Compared with passivation 10 d in SCP solutions with pH 13.5 and pH 12.5, the passive film on the surface of the rebar has good stability at pH 10.5, which indicates that the addition of Cr is beneficial to promote the corrosion resistance of the rebar. Full article

Water pollution caused by dyes is a significant environmental issue, necessitating the development of effective, cost-efficient decolorization methods suitable for industrial use. In this study, a Chitosan-Fe polymeric gel was synthesized, characterized, and tested for removing the azo dye Direct Red 83:1 from water. The polymeric magnetic chitosan was analyzed using various techniques: Field Emission Scanning Electron Microscopy (FE-SEM) revealed a porous structure, Differential Scanning Calorimetry (DSC) and Thermal Gravimetric Analysis (TGA) demonstrated the thermal stability, Infrared Spectrophotometry (IR) indicated the successful coordination of iron at the C3 position, and X-ray Powder Diffraction (XRD) confirmed the crystalline nature of the polymeric structure. Optimal conditions for kinetic and isotherm models were found at 1 g and pH 7.0. Adsorption behavior of Direct Red 83:1 onto magnetic chitosan gel beads was studied through kinetic tests and isotherm curves. The maximum adsorption capacity was 17.46 mg/g (qmax). The adsorption process followed pseudo-second-order kinetics (R² = 0.999) and fit the Temkin isotherm (R² = 0.946), suggesting heterogeneous surface adsorption. The newly synthesized Chitosan-Fe polymeric gel demonstrated good adsorption properties and facilitated easy separation of purified water. Full article