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Nanomaterials (Basel, Switzerland) May 2024Ensuring the stable operation of proton exchange membrane fuel cells is conducive to their real-world application. A promising direction for stabilizing electrodes is...
Ensuring the stable operation of proton exchange membrane fuel cells is conducive to their real-world application. A promising direction for stabilizing electrodes is the stabilization of the ionomer via the formation of surface compounds with graphene. A comprehensive study of the (electrochemical, chemical, and thermal) stability of composites for fuel cell electrodes containing a modifying additive of few-layer graphene was carried out. Electrochemical stability was studied by cycling the potential on a disk electrode for 5000 cycles. Chemical stability was assessed via the resistance of the composites to HO treatment using ion-selective potentiometry. Thermal stability was studied using differential thermal analysis. Composites were characterized by UV-Vis spectroscopy, Raman spectroscopy, EDX, and SEM. It was shown that graphene inhibits Nafion degradation when exposed to heat. Contrariwise, Nafion is corrosive to graphene. During electrochemical and chemical exposure, the determining change for carbon-rich composites is the carbon loss (oxidation) of the carbon material. In the case of carbon-poor composites, the removal of fluorine and sulfur from the Nafion polymer with their partial replacement by oxygen prevails. In all cases, the F/S ratio is stable. The dispersity of Nafion in a sample affects its chemical stability more than the G/Nafion ratio does.
PubMed: 38869547
DOI: 10.3390/nano14110922 -
Materials (Basel, Switzerland) May 2024The search for the ideal metallic material for an implant is still a difficult challenge for scientists due to the phenomenon of corrosion and the consequent disruption...
The search for the ideal metallic material for an implant is still a difficult challenge for scientists due to the phenomenon of corrosion and the consequent disruption of the implant structure. Prevention is the application of coatings that protect the implant, activate the tissues for faster regeneration, and also prevent inflammation through antibacterial and antiviral effects. The present study focuses on the selection of components for a Ti-6Al-4V alloy coating. These days, researchers are taking an intense interest in extracts of natural origin. It was decided to take a look at , which contains vitamins and valuable elements and is rich in polyphenols, as well as antioxidants. The composition of coatings based on a PEG polymer reinforced with brushite and the extract with the proteins L-carnosine, fibroin, or sericin was developed. The samples were subjected to detailed physiochemical analysis, including potentiometry and electrical conductivity analysis, Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis, and UV-VIS spectroscopy. The study demonstrated that polyphenols were successfully released from the coatings during incubation in vitro. The osteointegration process can be supported by a number of factors, such as the release of polyphenols from implant coatings to prevent bacterial, viral, and fungal infections. Subjecting the samples to 14 days of incubation demonstrated their interactions with the incubation fluids, an ion exchange between the medium and the materials. An analysis of the surface morphology exhibited the presence of brushite crystals and their increased number after incubation, indicating the bioactivity of the formed coatings.
PubMed: 38793317
DOI: 10.3390/ma17102250 -
Molecules (Basel, Switzerland) May 2024Bicyclic peptides have attracted the interest of pharmaceutical companies because of their remarkable properties, putting them on a new path in medicine. Their...
Bicyclic peptides have attracted the interest of pharmaceutical companies because of their remarkable properties, putting them on a new path in medicine. Their conformational rigidity improves proteolytic stability and leads to rapid penetration into tissues via any possible route of administration. Moreover, elimination of renal metabolism is of great importance, for example, for people with a history of liver diseases. In addition, each ring can function independently, making bicyclic peptides extremely versatile molecules for further optimization. In this paper, we compared the potentiometric and spectroscopic properties studied by UV-vis, MCD, and EPR of four synthetic analogues of the bi-cyclic peptide c(PKKHP-c(CFWKTC)-PKKH) (BCL). In particular, we correlated the structural and spectral properties of complexes with coordinating abilities toward Cu(II) ions of MCL1 (Ac-PKKHPc(CFWKTC)PKKH-NH) that contains the unbinding cycle and N- and C-terminal linear parts with two histidine residues, one per part; two monocyclic ligands containing one histidine residue, both in the N-terminal position, i.e., MCL2 (Ac-PKKHPc(CFWKTC)PKKS-NH) and in the C-terminal position, i.e., MCL3 (Ac-PKKSPc(CFWKTC)PKKH-NH), respectively; and the linear structure LNL (Ac-PKKHPSFWKTSPKKH-NH). Potentiometric results have shown that the bicyclic structure promotes the involvement of the side chain imidazole donors in Cu(II) binding. On the other hand, the results obtained for the mono-cyclic analogues lead to the conclusion that the coordination of the histidine moiety as an anchoring group is promoted by its location in the peptide sequence further from the nonbinding cycle, strongly influencing the involvement of the amide donors in Cu(II) coordination.
Topics: Copper; Peptides, Cyclic; Coordination Complexes; Ligands; Ions; Potentiometry
PubMed: 38792059
DOI: 10.3390/molecules29102197 -
Molecules (Basel, Switzerland) May 2024Copper(II), nickel(II) and zinc(II) complexes of various peptide fragments of tau protein were studied by potentiometric and spectroscopic techniques. All peptides...
Copper(II), nickel(II) and zinc(II) complexes of various peptide fragments of tau protein were studied by potentiometric and spectroscopic techniques. All peptides contained one histidyl residue and represented the sequences of tau(91-97) (Ac-AQPHTEI-NH), tau(385-390) (Ac-KTDHGA-NH) and tau(404-409) (Ac-SPRHLS-NH). Imidazole-N donors of histidine were the primary metal binding sites for all peptides and all metal ions, but in the case of copper(II) and nickel(II), the deprotonated amide groups were also involved in metal binding by increasing pH. The most stable complexes were formed with copper(II) ions, but the presence of prolyl residues resulted in significant changes in the thermodynamic stability and speciation of the systems. It was also demonstrated that nickel(II) and especially zinc(II) complexes have relatively low thermodynamic stability with these peptides. The copper(II)-catalyzed oxidation of the peptides was also studied. In the presence of HO, the fragmentation of peptides was detected in all cases. In the simultaneous presence of HO and ascorbic acid, the fragmentation of the peptide is less preferred, and the formation of 2-oxo-histidine also occurs.
Topics: Nickel; Copper; Zinc; tau Proteins; Coordination Complexes; Peptide Fragments; Oxidation-Reduction; Histidine; Hydrogen-Ion Concentration; Hydrogen Peroxide; Thermodynamics
PubMed: 38792033
DOI: 10.3390/molecules29102171 -
International Journal of Molecular... May 2024ferredoxin:NADP oxidoreductase (FNR) is a thioredoxin reductase-type FNR whose redox properties and reactivity with nonphysiological electron acceptors have been...
ferredoxin:NADP oxidoreductase (FNR) is a thioredoxin reductase-type FNR whose redox properties and reactivity with nonphysiological electron acceptors have been scarcely characterized. On the basis of redox reactions with 3-acetylpyridine adenine dinucleotide phosphate, the two-electron reduction midpoint potential of the flavin adenine dinucleotide (FAD) cofactor was estimated to be -0.240 V. Photoreduction using 5-deazaflavin mononucleotide (5-deazaFMN) as a photosensitizer revealed that the difference in the redox potentials between the first and second single-electron transfer steps was 0.024 V. We examined the mechanisms of the reduction of several different groups of non-physiological electron acceptors catalyzed by FNR. The reactivity of quinones and aromatic -oxides toward FNR increased when increasing their single-electron reduction midpoint redox potentials. The reactivity of nitroaromatic compounds was lower due to their lower electron self-exchange rate, but it exhibited the same trend. A mixed single- and two-electron reduction reaction was characteristic of quinones, whereas reactions involving nitroaromatics proceeded exclusively via the one-electron reduction reaction. The oxidation of FADH to FAD is the rate-limiting step during the oxidation of fully reduced FAD. The calculated electron transfer distances in the reaction with nitroaromatics were close to those of other FNRs including the plant-type enzymes, thus demonstrating their similar active site accessibility to low-molecular-weight oxidants despite the fundamental differences in their structures.
Topics: Oxidation-Reduction; Ferredoxin-NADP Reductase; Bacillus subtilis; Xenobiotics; Flavin-Adenine Dinucleotide; Bacterial Proteins; Potentiometry; Oxidants; Quinones; Electron Transport
PubMed: 38791410
DOI: 10.3390/ijms25105373 -
Scientific Reports May 2024This paper reports on the development of a flexible-wearable potentiometric sensor for real-time monitoring of sodium ion (Na), potassium ion (K), and pH in human sweat....
This paper reports on the development of a flexible-wearable potentiometric sensor for real-time monitoring of sodium ion (Na), potassium ion (K), and pH in human sweat. NaMnO, polyaniline, and KCo[Fe(CN)] were used as sensing materials for Na, H and K monitoring, respectively. The simultaneous potentiometric Na, K, and pH sensing were carried out by the developed sensor, which enables signal collection and transmission in real-time to the smartphone via a Wi-Fi access point. Then, the potentiometric responses were evaluated by a designed android application. Na, K, and pH sensors illustrated high sensitivity (59.7 ± 0.8 mV/decade for Na, 57.8 ± 0.9 mV/decade for K, and 54.7 ± 0.6 mV/pH for pH), excellent stability, and good batch-to-batch reproducibility. The results of on-body experiments demonstrated that the proposed platform is capable of real-time monitoring of the investigated ions.
Topics: Humans; Hydrogen-Ion Concentration; Potentiometry; Wearable Electronic Devices; Sodium; Sweat; Potassium; Biosensing Techniques; Wireless Technology; Smartphone; Reproducibility of Results
PubMed: 38773136
DOI: 10.1038/s41598-024-62236-3 -
BMC Oral Health May 2024Releasing of metal ions might implicate in allergic reaction as a negative subsequent of the corrosion of Stainless Steel (SS304) orthodontic wires. The aim of this...
BACKGROUND
Releasing of metal ions might implicate in allergic reaction as a negative subsequent of the corrosion of Stainless Steel (SS304) orthodontic wires. The aim of this study was to evaluate the corrosion resistance of zinc-coated (Zn-coated) SS orthodontic wires.
METHODS
Zinc coating was applied on SS wires by PVD method. Electrochemical impedance spectroscopy (EIS), Potentiodynamic polarization tests and Tafel analysis methods were used to predict the corrosion behavior of Zn-coated and uncoated SS wires in both neutral and acidic environments.
RESULTS
The values of E ,i and Rwhich were the electrochemical corrosion characteristics, reported better corrosion behavior of Zn-coated SS wires against uncoated ones in both artificial saliva and fluoride-containing environments. Experimental results of the Tafel plot analyses were consistent with that of electrochemical impedance spectroscopy analyses for both biological solutions.
CONCLUSION
Applying Zn coating on bare SS orthodontic wire by PVD method might increase the corrosion resistance of the underlying stainless-steel substrate.
Topics: Corrosion; Stainless Steel; Orthodontic Wires; Zinc; Dielectric Spectroscopy; Saliva, Artificial; Materials Testing; Dental Alloys; Coated Materials, Biocompatible; Fluorides; Hydrogen-Ion Concentration; Humans; Surface Properties; Potentiometry
PubMed: 38725023
DOI: 10.1186/s12903-024-04242-5 -
Journal of Inorganic Biochemistry Jul 2024The clinical success of [Ra]RaCl (Xofigo®) for the palliative treatment of bone metastases in patients with prostate cancer has highlighted the therapeutic potential of...
Navigating through the coordination preferences of heavy alkaline earth metals: Laying the foundations for Ra- and Ba-based targeted alpha therapy and theranostics of cancer.
The clinical success of [Ra]RaCl (Xofigo®) for the palliative treatment of bone metastases in patients with prostate cancer has highlighted the therapeutic potential of α-particle emission. Expanding the applicability of radium-223 in Targeted Alpha Therapy of non-osseous tumors is followed up with significant interest, as it holds the potential to unveil novel treatment options in the comprehensive management of cancer. Moreover, the use of barium radionuclides, like barium-131 and -135m, is still unfamiliar in nuclear medicine applications, although they can be considered as radium-223 surrogates for imaging purposes. Enabling these applications requires the establishment of chelators able to form stable complexes with radium and barium radionuclides. Until now, only a limited number of ligands have been suggested and these molecules have been primarily inspired by existing structures known for their ability to complex large metal cations. However, a systematic inspection of chelators specifically tailored to Ra and Ba has yet to be conducted. This work delves into a comprehensive investigation of a series of small organic ligands, aiming to unveil the coordination preferences of both radium-223 and barium-131/135m. Electronic binding energies of both metal cations to each ligand were theoretically computed via Density Functional Theory calculations (COSMO-ZORA-PBE-D3/TZ2P), while thermodynamic stability constants were experimentally determined for Ba-ligand complexes by potentiometry, NMR and UV-Vis spectroscopies. The outcomes revealed malonate, 2-hydroxypyridine 1-oxide and picolinate as the most favorable building blocks to design multidentate chelators. These findings serve as foundation guidelines, propelling the development of cutting-edge radium-223- and barium-131/135m-based radiopharmaceuticals for Targeted Alpha Therapy and theranostics of cancer.
Topics: Radium; Humans; Radioisotopes; Coordination Complexes; Barium; Alpha Particles; Chelating Agents; Neoplasms; Theranostic Nanomedicine; Metals, Alkaline Earth; Radiopharmaceuticals
PubMed: 38701687
DOI: 10.1016/j.jinorgbio.2024.112569 -
Analytica Chimica Acta Jun 2024The Caco-2 cells were used as intestinal epithelial cell model to illustrate the hyperuricemia (HUA) mechanism under the co-culture of the imbalanced intestinal...
The Caco-2 cells were used as intestinal epithelial cell model to illustrate the hyperuricemia (HUA) mechanism under the co-culture of the imbalanced intestinal microbiome in this work. The uric acid (UA) concentration in the HUA process was monitored, and could be up to 425 μmol/L at 8 h co-cultured with the imbalanced intestinal microbiome. Single-cell potentiometry based on ion-selective microelectrode was used to study extracellular calcium change, which is hypothesized to play an important role in the UA excretion. The potential signal of the calcium in the extremely limited microenvironment around single Caco-2 cell was recorded through the single-cell analysis platform. The potential signal of sharp decrease and slow increase followed within a few seconds indicates the sudden uptake and gradually excretion process of calcium through the cell membrane. Moreover, the value of the potential decrease increases with the increase of the time co-cultured with the imbalanced intestinal microbiome ranging from 0 to 8 h. The Ca concentration around the cell membrane could decrease from 1.3 mM to 0.4 mM according to the potential decrease of 27.0 mV at the co-culture time of 8 h. The apoptosis ratio of the Caco-2 cells also exhibits time dependent with the co-culture of the imbalanced intestinal microbiome, and was 39.1 ± 3.6 % at the co-culture time of 8 h, which is much higher than the Caco-2 cells without any treatment (3.9 ± 2.9 %). These results firstly provide the links between the UA excretion with the apoptosis of the intestinal epithelial cell under the interaction of the imbalanced intestinal microbiome. Moreover, the apoptosis could be triggered by the calcium signaling.
Topics: Humans; Caco-2 Cells; Coculture Techniques; Calcium; Microelectrodes; Potentiometry; Carbon; Gastrointestinal Microbiome; Single-Cell Analysis; Apoptosis
PubMed: 38692795
DOI: 10.1016/j.aca.2024.342615 -
International Journal of Molecular... Apr 2024nitroreductase A (NfsA) is a candidate for gene-directed prodrug cancer therapy using bioreductively activated nitroaromatic compounds (ArNO). In this work, we...
nitroreductase A (NfsA) is a candidate for gene-directed prodrug cancer therapy using bioreductively activated nitroaromatic compounds (ArNO). In this work, we determined the standard redox potential of FMN of NfsA to be -215 ± 5 mV at pH 7.0. FMN semiquinone was not formed during 5-deazaflavin-sensitized NfsA photoreduction. This determines the two-electron character of the reduction of ArNO and quinones (Q). In parallel, we characterized the oxidant specificity of NfsA with an emphasis on its structure. Except for negative outliers nitracrine and SN-36506, the reactivity of ArNO increases with their electron affinity (single-electron reduction potential, ) and is unaffected by their lipophilicity and Van der Waals volume up to 386 Å. The reactivity of quinoidal oxidants is not clearly dependent on , but 2-hydroxy-1,4-naphthoquinones were identified as positive outliers and a number of compounds with diverse structures as negative outliers. 2-Hydroxy-1,4-naphthoquinones are characterized by the most positive reaction activation entropy and the negative outlier tetramethyl-1,4-benzoquinone by the most negative. Computer modelling data showed that the formation of H bonds with Arg15, Arg133, and Ser40, plays a major role in the binding of oxidants to reduced NfsA, while the role of the π-π interaction of their aromatic structures is less significant. Typically, the calculated hydride-transfer distances during ArNO reduction are smallwer than for Q. This explains the lower reactivity of quinones. Another factor that slows down the reduction is the presence of positively charged aliphatic substituents.
Topics: Nitroreductases; Prodrugs; Substrate Specificity; Escherichia coli; Oxidation-Reduction; Escherichia coli Proteins; Potentiometry; Catalysis; Molecular Docking Simulation
PubMed: 38673999
DOI: 10.3390/ijms25084413