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Nefrologia Jun 2024Changes in plasma sodium concentration (Na, expressed in mEq/L) are common in hemodialysis (HD) patients. Hemodialysis monitors can estimate Na by using an internal...
INTRODUCTION
Changes in plasma sodium concentration (Na, expressed in mEq/L) are common in hemodialysis (HD) patients. Hemodialysis monitors can estimate Na by using an internal algorithm based on ion dialysance measurements. The present study studies the accuracy of the correlation between the Na estimated by the dialysis monitor and that measured by the biochemistry laboratory at our center.
MATERIAL AND METHODS
A single-centre prospective observational study in patients on a chronic HD program with the 6008 CAREsystem monitor and standard sodium (138mmol/L) and bicarbonate (32mmol/L) prescriptions. Venous blood samples were drawn from each patient before and after each HD session to ensure inter- and intra-individual validity. The Na was measured in the biochemistry laboratory using indirect potentiometry and simultaneously the estimated Na by the HD monitor was recorded at the beginning and at the end of the HD session. For statistical analysis, a scatterplot was made, and Spearman's correlation quotient was calculated. In addition, the differences between both methods were represented as Bland-Altman diagrams.
RESULTS
The pre-dialysis Na measured in the laboratory was 137.49±3.3, and that of the monitor, 137.96±2.91, with a correlation with R value of 0.683 (p<0.001). The post-dialysis Na measured in the laboratory was 137.08±2.23, and that of the monitor was 138.87±1.88, with an R of 0.442 (p<0.001). On the Bland-Altman plots, the pre-dialysis Na has a systematic error of 0.49, in favor of the monitor-estimated Na, with a 95% confidence interval (CI) of (-3.24 to a 4.22). In the post-dialysis Na, a systematic error of 1.79 with a 95% CI of (-1.64 to 5.22) was obtained.
CONCLUSION
The correlation between the Na estimated by Fresnius 6008 CAREsystem HD monitor and that measured by the laboratory is good, especially pre-dialysis measurements. Further studies should verify the external validity of these results.
PubMed: 38890062
DOI: 10.1016/j.nefroe.2023.09.008 -
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 -
Inorganic Chemistry Jun 2024Phytochelatins (PCs) are poly-Cys peptides containing a repeating γ-Glu-Cys motif synthesized in plants, algae, certain fungi, and worms by PC synthase from reduced...
Phytochelatins Bind Zn(II) with Micro- to Picomolar Affinities without the Formation of Binuclear Complexes, Exhibiting Zinc Buffering and Muffling Rather than Storing Functions.
Phytochelatins (PCs) are poly-Cys peptides containing a repeating γ-Glu-Cys motif synthesized in plants, algae, certain fungi, and worms by PC synthase from reduced glutathione. It has been shown that an excess of toxic metal ions induces their biosynthesis and that they are responsible for the detoxification process. Little is known about their participation in essential metal binding under nontoxic, basal conditions under which PC synthase is active. This study presents spectroscopic and thermodynamic interactions with the PC2-PC5 series, mainly focusing on the relations between Zn(II) complex stability and cellular Zn(II) availability. The investigations employed mass spectrometry, UV-vis spectroscopy, potentiometry, competition assays with zinc probes, and isothermal titration calorimetry (ITC). All peptides form ZnL complexes, while ZnL was found only for PC2, containing two to four sulfur donors in the coordination sphere. Binuclear species typical of Cd(II)-PC complexes are not formed in the case of Zn(II). Results demonstrate that the affinity for Zn(II) increases linearly from PC2 to PC4, ranging from micro- to low-picomolar. Further elongation does not significantly increase the stability. Stability elevation is driven mainly by entropic factors related to the chelate effect and conformational restriction rather than enthalpic factors related to the increasing number of sulfur donors. The affinity of the investigated PCs falls within the range of exchangeable Zn(II) concentrations (hundreds of pM) observed in plants, supporting for the first time a role of PCs both in buffering and in muffling cytosolic Zn(II) concentrations under normal conditions, not exposed to zinc excess, where short PCs have been identified in numerous studies. Furthermore, we found that Cd(II)-PC complexes demonstrate significantly higher metal capacities due to the formation of polynuclear species, which are lacking for Zn(II), supporting the role of PCs in Cd(II) storage (detoxification) and Zn(II) buffering and muffling. Our results on phytochelatins' coordination chemistry and thermodynamics are important for zinc biology and understanding the molecular basis of cadmium toxicity, leaving room for future studies.
Topics: Phytochelatins; Zinc; Thermodynamics; Coordination Complexes
PubMed: 38845098
DOI: 10.1021/acs.inorgchem.4c01707 -
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