Search

Ctr1 is a membrane-spanning homotrimer that facilitates copper uptake in eukaryotic cells with high affinity. While structural details of the transmembrane domain of human Ctr1 have been elucidated using X-ray crystallography and cryo-EM, the transfer mechanisms of copper and the conformational changes that control the gating mechanism remain poorly understood. The role of the extracellular N-terminal domains is particularly unclear due to the absence of a high-resolution structure of the full-length hCtr1 protein and limited biochemical and biophysical characterization of the transporter in solution and in cell. In this study, we employed distance electron paramagnetic resonance to investigate the conformational changes of the extracellular N-terminal domain of full-length hCtr1, both in vitro and in cells, as a function of Cu(I) binding. Our results demonstrate that at specific Cu(I) concentrations, the extracellular chains move closer to the lumen to facilitate copper transfer. Additionally, while at these concentrations the intracellular part is penetrating the lumen, suggesting a ball-and-chain gating mechanism. Moreover, this phenomenon was observed for both reconstituted protein in micelles and in native cell membranes. However, the measured distance values were slightly different, suggesting that the membrane's characteristics and therefore its lipid composition also impact and even regulate the gating mechanism of hCtr1. [ABSTRACT FROM AUTHOR]

In‐cell measurements of the relationship between structure and dynamics to protein function is at the forefront of biophysics. Recently, developments in EPR methodology have demonstrated the sensitivity and power of this method to measure structural constraints in‐cell. However, the need to spin label proteins ex‐situ or use noncanonical amino acids to achieve endogenous labeling remains a bottleneck. In this work we expand the methodology to endogenously spin label proteins with Cu(II) spin labels and describe how to assess in‐cell spin labeling. We quantify the amount of Cu(II)‐NTA in cells, assess spin labeling, and account for orientational effects during distance measurements. We compare the efficacy of using heat‐shock and hypotonic swelling to deliver spin label, showing that hypotonic swelling is a facile and reproducible method to efficiently deliver Cu(II)‐NTA into E. coli. Notably, over six repeats we accomplish a bulk average of 57 μM spin labeled sites, surpassing existing endogenous labeling methods. The results of this work open the door for endogenous spin labeling that is easily accessible to the broader biophysical community. [ABSTRACT FROM AUTHOR]

The combination of continuous wave electron paramagnetic resonance (cw‐EPR) with electrochemistry is highly attractive as it allows a clean in‐situ generation and the subsequent spectroscopic characterisation of radical ions, which are important intermediates in many photocatalytic cycles as well as light‐induced processes occurring in biological systems or optoelectronic devices. Although commercial setups for spectroelectrochemical EPR are available, they are often expensive and tailored to a particular spectroscopic setup. Here we present a design for a low‐cost electrochemical EPR cell that can be used in combination with any commercial cw‐EPR instrumentation. The cell design is compared to existing setups and the performance of the cell is evaluated by comparison of EPR spectra obtained by chemical and electrochemical oxidation of a graphene fragment. [ABSTRACT FROM AUTHOR]

Copper‐exchanged zeolite omega (Cu‐omega) is a potent material for the selective conversion of methane‐to‐methanol (MtM) via the oxygen looping approach. However, its performance exhibits substantial variation depending on the operational conditions. Under an isothermal temperature regime, Cu‐omega demonstrates subdued activity below 230 °C, but experiences a remarkable increase in activity at 290 °C. Applying a high‐temperature activation protocol at 450 °C causes a rapid deactivation of the material. This behavioral divergence is investigated by combining reactivity studies, neutron diffraction and in situ high‐resolution anomalous X‐ray powder diffraction (HR‐AXRPD), as well as electron paramagnetic resonance spectroscopy, to reveal that the migration of Cu throughout the framework is the primary cause of these behaviors, which in turn is predominantly governed by the degree of hydration of the system. This work suggests that control over the Cu migration throughout the zeolite framework may be harnessed to significantly increase the activity of Cu‐omega by generating more active sites for the MtM conversion. These results underscore the power of in situ HR‐AXRPD for unraveling the behavior of materials under reaction conditions and suggest that a re‐evaluation of Cu‐zeolites priorly deemed inactive for the MtM conversion across a broader range of conditions and looping protocols may be warranted. [ABSTRACT FROM AUTHOR]

New chamber stapes prosthesis (ChSP) is a middle-ear prosthesis intended for use in ear surgery for restoring the patient's middle ear function. As the prosthesis is an implantable medical device, it must be sterilized before use. However, possible alterations in the material and the functional properties following the sterilization process can influence the safety aspects while using the prosthesis. The purpose of this paper was to determine the effects of ionizing radiation (IR) on the physicochemical and biological properties of the new chamber prosthesis by utilizing EPR spectroscopy, mechanical testing, and cytotoxicity studies. Our research shows that the radiation treatment increases the hardness and the elastic modulus of the polymer, decreases the stiffness of the prosthesis membrane, and does not cause chemical changes in the polymers that may result in cytotoxicity. Furthermore, new ChSPs were successfully tested in preclinical in vitro tests. The test results justify the undertaking of further work, including in vivo biocompatibility tests and clinical trials, which would eventually lead to the increased use of the prosthesis in clinical practice. [ABSTRACT FROM AUTHOR]

Investigation of a published route to produce 3,5-di-tert-butylphenol, starting from commercial 3,5-di-tert-butylbenzoic acid via 3,5-di-tert-butylanlinium hydrogen sulfate, unexpectedly yielded 2,6-dintitro-3,5-di-tert-butylphenol. Attempts to increase the yield of the latter resulted, instead, in the previously unreported 2,6-dinitro-3,5-di-tert-butylcyclohexa-2,5-dien-1,4-dione. Single-crystal X-ray diffraction structures are reported for the anilinium salt, the nitrated phenol, and the quinone. Voltammetry of the quinone shows two chemically reversible reductions in anhydrous solution and the radical anion produced from the first reduction step has been characterized by electron paramagnetic resonance spectroscopy. This compound fits well to the middle range of electron-poor quinones, indicating that the inductive effects of the tert-butyl and nitro groups counteract each other. This conclusion is also supported by the infrared spectroscopic data where the ν(C=O) and ν(C=C) bands are of very similar energy to those of 2,3,5,6-tetrachloro-1,4-benzoquinone. [ABSTRACT FROM AUTHOR]

Nitroxides are stable organic radicals with exceptionally long lifetimes, which render them uniquely suitable as observable probes or polarising agents for spectroscopic investigation of biomolecular structure and dynamics. Radical‐based probes for biological applications are ideally characterized by both robustness towards reductive degradation and beneficial electron spin relaxation parameters. These properties are largely influenced by the molecular structure of the nitroxide scaffold, and also by the conformations it prefers to adopt. In this study we present the synthesis of the first nitroxides based on a spirocyclic pyrrolidine scaffold with an exocyclic methylene substituent. The conformations adopted by these nitroxides were evaluated by X‐ray crystallography, both with single nitroxide crystals and by inclusion of nitroxides in a microporous crystalline sponge. The kinetic and thermodynamic stability of the new nitroxides towards reduction was investigated by electron paramagnetic resonance (EPR) spectroscopy and cyclic voltammetry (CV). In combination with EPR measurements of electron spin relaxation properties, these results suggest that this new family of nitroxides can provide access to multifunctionalized probes and polarising agents suitable for use in biological environments at elevated temperatures. [ABSTRACT FROM AUTHOR]

Mixed phosphonium-iodonium ylides are of interest as reactants for the synthesis of new heterocyclic compounds. Recently it has been shown that under irradiation the reactions of phosphonium-iodonium ylides occur with the formation of radicals. The radicals generated in the photolysis of the ylide itself and its fragments, diphenyliodonium salt and triphenylphosphine, or compounds participating in its reactions, dichloromethane and phenylacetylene, are studied with the use of PBN and DMPO spin traps. The obtained results confirm the radical mechanism of the ylide photodecomposition and have allowed us to specify the composition of the primary radicals generated in the photolysis. The unknown EPR parameters of spin adducts are determined for some radicals. [ABSTRACT FROM AUTHOR]

Annulation of mixed phosponium‐iodonium ylides and compounds with a triple bond is an interesting example of the synthesis of different types of heterocycles in one‐pot, metal‐free systems at ambient temperature to give substituted oxazoles in the reaction with nitriles and phosphorus‐containing λ5‐phosphinolines and substituted furans in the reaction with acetylenes. The iodonium group in the mixed ylides provides the possibility for the radical initiation of the reaction. Herein, we investigated the generation of primary radicals and the formation of phosphorus‐containing products in the photolysis of benzoyl phosphonium‐iodonium ylide alone and in its reaction with acetylenes in DCM by EPR and 31P NMR spectroscopies with the use of two most popular spin traps, PBN and DMPO. The results allowed us to account the crucial difference in the registered radicals in the two systems for the aggregation of the components, with ylide molecules forming a core and acetylene molecules being a shell of the aggregates in DCM, in which the annulation occurs. The peculiarities of the reactions of PBN and DMPO with generated radicals are discussed. [ABSTRACT FROM AUTHOR]

Electron paramagnetic resonance (EPR) spectroscopy has long been established across various scientific disciplines for characterizing organic radicals, organometallic complexes, protein structures and dynamics, polymerization processes, and radical degradation phenomena. Despite its extensive utility in these areas, EPR spectroscopy’s application within pharmaceutical science has historically been constrained, primarily due to factors such as high equipment costs, a steep learning curve, complex spectral deconvolution and analysis, and a traditional lack of emphasis on single-electron chemistry in pharmaceutical research. This review aims to provide a thorough examination of EPR spectroscopy’s applications in analyzing a wide array of para-magnetic species relevant to pharmaceutical research. We detail how EPR spectroscopy can be employed to assess free radical scavenging properties in pharmaceutical compounds, elucidate drug mechanisms of action, and explore pharmacokinetics. Additionally, we investigate the role of free radicals in drug-induced toxicity and drug-membrane interactions, while also covering the application of EPR spectroscopy in drug delivery research, advanced studies of metallodrugs, and monitoring of oxygen levels in biological systems through EPR oximetry. The recent advancements in the miniaturization of EPR spectro meters have paved the way for their application in on-site and in-line mo nitoring during the manufacturing process and quality control of pharmaceutical substances and final drug formulations due to being the only direct and non-invasive detection technique for radical detection.

The poor prognosis of glioblastoma multiforme, inadequate treatment options, and growing drug resistance urge the need to find new effective agents. Due to the significant anti-cancer potential of harmicens, hybrid compounds which comprise harmine/β-carboline and ferrocene moiety, we investigated their antiglioblastoma potential in vitro and mechanism of action (inhibition of DYRK1A, Hsp90, anti-oxidative activity). The results have shown that triazole-type harmicens, namely ., with a ferrocene moiety in C-3 position of the β-carboline ring (IC50 = 3.7 ± 0.1 µmol L–1, SI = 12.6) and ., the C-6 substituted harmicene (IC50 = 7.4 ± 0.5 µmol L–1, SI = 5.8) exert remarkable activity and selectivity against human malignant glioblastoma cell line (U251) in vitro. On the other hand, amide-type harmicens 10, 12, and 14 exhibited strong, but non-selective activity, in the low micro-molar range. Mechanistic studies revealed that among active compounds, amide-type harmicens 12 and 14 inhibit DYRK1A and Hsp90 CTD, whereas compound 14 showed pronounced antioxidative activity. Therefore, the antiproliferative activity of harmicens might be a combination of complex molecular interactions.

Despite the significant development and extensive application of phthalocyanine and related azaporphyrins, little attention has been paid to meso‐N‐substituted azaporphyrinoids. Here, we report new derivatives of 5,10,20‐triaryl‐5,15‐diazaporphyrinoids (Ar3DAP), which are reversibly redox‐switchable between the 18π‐ and 19π‐electron state. Four kinds of metal(II) complexes and free bases of Ar3DAP were prepared by metal‐templated cyclization of metal(II) complexes of 5,10,15‐triaryl‐10‐azabiladiene‐ac with sodium azide or copper‐catalyzed N‐phenylation of 10,20‐diaryl‐5,15‐diazaporphyrins (Ar2DAP) with diphenyliodonium hexafluorophosphate. In particular, regioselective N‐phenylation of covalently linked Ar2DAP dimer afforded two kinds of dimers bearing one or two meso‐N‐phenyl groups. Cyclic voltammetry revealed that attaching one aryl group onto the meso‐nitrogen atom markedly changed the redox potentials of the DAP ring. The aromaticity and optical properties of the new Ar3DAP π‐electron systems were assessed using various spectroscopic measurements and density functional theory calculations. The distribution pattern of an electron spin in the neutral Ar2DAP–Ar3DAP radical revealed that the meso‐N‐phenyl group had a remarkable effect on spin delocalization of DAP π‐radical. The present study provides valuable information for understanding the effects of the number of meso‐N‐substituents on azaporphyrin‐based π‐electron systems. [ABSTRACT FROM AUTHOR]

Herein, we report the synthesis and properties of triptycene‐based C3v‐ and Cs‐symmetric stable triradicals. SQUID magnetometry showed the propeller‐shaped triradicals were both an antiferromagnetic equilateral triangle spin system with small spin‐spin interactions J/kB~−120 K and −106 K, leading to ca. 4/6 coexistence of the doublet/quartet states in thermal equilibrium at room temperature. The triradicals exhibited characteristic NIR absorption bands reaching 1000 nm, which was solely ascribed to the triradical in the doublet state by variable‐temperature spectroscopic studies and quantum chemical calculations. Taking advantage of the spin‐specific absorption feature, we found that the triradicals in the low‐spin state undergo symmetry‐breaking charge transfer, while those in the high‐spin state fall into a monoradical‐like excited state. [ABSTRACT FROM AUTHOR]

Reaction of a molecular zinc–hydride [{(ArNCMe)2CH}ZnH] (Ar=2,6‐di‐isopropylphenyl) with 0.5 equiv. of [Ni(CO)Cp]2 led to the isolation of a nickel–zinc hydride complex containing a bridging 3‐centre,2‐electron Ni−H−Zn interaction. This species has been characterized in the solid‐state by single crystal X‐ray diffraction. DFT calculations are consistent with its formulation as a σ‐complex derived from coordination of the zinc–hydride to a paramagnetic nickel(I) fragment. Continuous‐wave and pulse EPR experiments suggest that this species is labile in solution. Further experiments show that in the presence of catalytic quantities of nickel(I) precursors, zinc–hydride bonds can undergo either H/D‐exchange with D2 or dehydrocoupling to form Zn−Zn bonds. In combination, the data support the activation and functionalisation of zinc–hydride bonds at nickel(I) centres. [ABSTRACT FROM AUTHOR]

The local environment of Yb3+ ions doped into ceria (CeO 2) nanoparticles, synthesized by two different methods, was determined using EPR spectroscopy. It was found that the charge compensator for the Yb3+ ion located in the nearest environment can be a vacancy, a hydroxyl group, or a fluorine ion. The EPR spectra of Yb3+ ions at concentrations of 0.1 mol% and 0.5 mol% in ceria nanoparticles, prepared using the coprecipitation technique from an aqueous solution, are mainly due to cubic sites, which indicate the remote location of the charge compensators. The EPR lines resulting from trigonal sites in these samples suggested that the charge compensation is associated with a hydroxyl group. The FTIR measurements correlate with this supposition. After annealing the samples in a vacuum furnace, EPR lines from trigonal sites related to oxygen vacancies were observed. The second type of ceria nanoparticle was prepared by annealing CeF 3 nanoparticles in air. EPR spectra of Yb³⁺ ions at concentrations of 0.1 mol% and 0.5 mol% in these samples revealed that the lines from trigonal sites were mainly associated with fluorine ions in the nearest environment. [ABSTRACT FROM AUTHOR]

With rational designability, versatile tunability, and quantum coherence, molecular electron spin qubits could offer new opportunities for quantum information science, enabling simplified implementation of quantum algorithms and chemical‐specific quantum sensing. The development of these transformative technologies relies on coherent addressing of single molecular electron spin qubits with high initialization, manipulation, and readout fidelities. This is unfeasible to conventional electron spin resonance spectroscopy, which is widely used for coherent addressing of ensemble electron spins, due to its low initialization efficiency and readout sensitivity. Taking advantage of single spin detectability of single‐molecule spectroscopy, scanning tunneling microscopy, atomic force microscopy, and quantum metrology, several strategies have been developed to empower electron spin resonance spectroscopy with single qubit addressability. In this Emerging Topic, we introduce principles and technical implementation of strategies for coherent addressing of single molecular electron spin qubits, discuss their potential applicability in quantum technologies, and point out their challenges in terms of scalability, molecular design, and/or decoherence suppression. We discuss future directions to overcome these challenges and to improve single qubit addressing technologies, which will facilitate the advancement of molecular quantum information science. [ABSTRACT FROM AUTHOR]

New cobalt(II)‐based complexes with [N2O2] coordination formed by two bis‐chelate ligands were synthesized and characterized by a multi‐technique approach. The complexes possess an easy‐axis anisotropy (D<0) and magnetic measurements show a field‐induced slow relaxation of magnetization. The spin‐reversal barriers, i. e., the splitting of the two lowest Kramers doublets (UZFS), have been measured by THz‐EPR spectroscopy, which allows to distinguish the two crystallographically independent species present in one of the complexes. Based on these experimental UZFS energies together with those for related complexes reported in literature, it was possible to establish magneto‐structural correlations. UZFS linearly depends on the elongation parameter ϵT of the (pseudo‐)tetrahedral coordination, which is given by the ratio between the average obtuse and acute angles at the cobalt(II) ion, while UZFS was found to be virtually independent of the twist angle of the chelate planes. With increasing deviation from the orthogonality of the latter, the rhombicity (|E/D|) increases. [ABSTRACT FROM AUTHOR]

Air‐stable cyclometalated palladium(II) complexes with benzamide ligands were synthesized in high yields and characterized by X‐ray diffraction analysis, CVA, 1H NMR, 13C NMR spectroscopy, MALDI‐MS, and ESI‐MS. The electrochemical oxidation of the complexes is reversible in the presence of a quinoline substituent in the ligand and gives Pd (III) species that do not undergo reductive elimination and are detectable by ESR spectroscopy. The complexes showed high cytotoxicity against cervical cancer (M‐HeLa) and duodenal adenocarcinoma (HuTu 80), a human mammary ductal adenocarcinoma line (MCF‐7) and a human lung carcinoma cell line (A549). The possibility of generating reactive oxygen species in solution (such as OH−radicals), which can be responsible for the antitumor activity of the studied complexes, using the ESR method was shown. [ABSTRACT FROM AUTHOR]

The use of organic molecules as photosensitizers in photoredox catalysis is an attractive research field as it has the potential to replace conventionally used photosensitizers, which are based on rare metals. In the context of light‐driven hydrogen evolution catalysis, the radical formation of two perylene monoimide dyes (PMIs) was studied by means of electron paramagnetic resonance (EPR) and UV/Vis spectroscopy. The PMIs were reduced and oxidized both photochemically and electrochemically to study the changes in absorption and EPR signature. A distinct differentiation between the two PMIs as well as a comparison between the oxidative and reductive processes can be made by EPR measurements. UV/Vis measurements showed different features under redox conditions. This study addresses a gap in understanding the radical intermediate formation during photocatalytic processes. [ABSTRACT FROM AUTHOR]

Respiratory complex I (R‐CI) is an essential enzyme in the mitochondrial electron transport chain but also a major source of reactive oxygen species (ROS), which are implicated in neurodegenerative diseases and ageing. While the mechanism of ROS production by R‐CI is well‐established, the feedback of ROS on R‐CI activity is poorly understood. Here, we perform EPR spectroscopy on R‐CI incorporated in artificial membrane vesicles to reveal that ROS (particularly hydroxyl radicals) reduce R‐CI activity by making the membrane more polar and by increasing its hydrogen bonding capability. Moreover, the mechanism that we have uncovered reveals that the feedback of ROS on R‐CI activity via the membrane is transient and not permanent; lipid peroxidation is negligible for the levels of ROS generated under these conditions. Our successful use of modular proteoliposome systems in conjunction with EPR spectroscopy and other biophysical techniques is a powerful approach for investigating ROS effects on other membrane proteins. [ABSTRACT FROM AUTHOR]

Being a low‐toxic and hydrophilic representative of TAM, OX063 has shown its suitability for in‐vivo and in‐cell EPR experiments and design of spin labels. Using 13C labeling, we investigated the course of oxidative degradation of OX063 into quinone‐methide (QM) under the influence of superoxide as well as further thiol‐promoted reduction of QM into TAM radical, which formally corresponds to substitution of a carboxyl function by a hydroxyl group. We found these transformations being quantitative in model reactions mimicking specific features of biological media and confirmed the presence of these reactions in the blood and liver homogenate of mice in vitro. The emergence of the trityl with the hydroxyl group can be masked by an initial TAM in EPR spectra and may introduce distortions into EPR‐derived oximetry data if they have been obtained for objects under hypoxia. 13C labeling allows one to detect its presence, considering its different hyperfine splitting constant on 13C1 (2.04 mT) as compared to OX063 (2.30 mT). The potential involvement of these reactions should be considered when using TAM in spin‐labeling of biopolymers intended for subsequent EPR experiments, as well as in the successful application of TAM in experiments in vivo and in cell. [ABSTRACT FROM AUTHOR]

New active ingredients, including those of plant origin, which could protect the skin against various harmful factors, such as UV radiation and free radicals responsible for skin ageing, are still being sought. The present study was focused on the antioxidant activity of Hippophaë rhamnoides L. and Vaccinium oxycoccos L. fruit glycolic extracts. Investigations were also carried out to evaluate the effect of UVA radiation and the storage of the sea buckthorn and European cranberry extracts at an elevated temperature of 50 °C on their interactions with free radicals. The kinetics of the interactions of the extracts with DPPH were assessed using electron paramagnetic resonance (EPR) spectroscopy. The sea buckthorn and European cranberry extracts quench the EPR signal of DPPH free radicals, which indicates their antioxidant potential. The EPR method further showed that a mixture of sea buckthorn and cranberry extracts in a volume ratio of 2:1 was more potent in quenching free radicals compared to a mixture of these extracts in a ratio of 1:2. Our findings demonstrate that long-term UVA radiation exposure reduces the ability of sea buckthorn and cranberry extracts to interact with free radicals. Moreover, storage at elevated temperatures does not affect the interaction of sea buckthorn extract with free radicals, while it alters the ability of cranberry extract to interact with free radicals. This study has demonstrated that an important factor in maintaining the ability to scavenge radicals is the storage of raw materials under appropriate conditions. H. rhamnoides and V. oxycoccos extracts can be used as valuable raw materials with antioxidant properties in the pharmaceutical and cosmetic industries. [ABSTRACT FROM AUTHOR]

Cladosporium cladosporioides are the pigmented soil fungi containing melanin. The aim of this work was to determine the influence of amphotericin B on free radicals in the natural melanin isolated from pigmented fungi Cladosporium cladosporioides and to compare it with the effect in synthetic DOPA-melanin. Electron paramagnetic resonance (EPR) spectra were measured at X-band (9.3 GHz) with microwave power in the range of 2.2–70 mW. Amplitudes, integral intensities, linewidths of the EPR spectra, and g factors, were analyzed. The concentrations of free radicals in the tested melanin samples were determined. Microwave saturation of EPR lines indicates the presence of pheomelanin in addition to eumelanin in Cladosporium cladosporioides. o-Semiquinone free radicals in concentrations ~1020 [spin/g] exist in the tested melanin samples and in their complexes with amphotericin B. Changes in concentrations of free radicals in the examined synthetic and natural melanin point out their participation in the formation of amphotericin B binding to melanin. A different influence of amphotericin B on free radical concentration in Cladosporium cladosporioides melanin and in DOPA-melanin may be caused by the occurrence of pheomelanin in addition to eumelanin in Cladosporium cladosporioides. The advanced spectral analysis in the wide range of microwave powers made it possible to compare changes in the free radical systems of different melanin polymers. This study is important for knowledge about the role of free radicals in the interactions of melanin with drugs. [ABSTRACT FROM AUTHOR]

Lactobacillus species are widely recognized for their probiotic potential, focusing on their mechanisms of health benefits and protection. Here we conducted an in vitro investigation of the probiotic potential with a role in microbiome homeostasis of four strains: Lactiplantibacillus plantarum L6 and F53, Ligilactobacillus salivarius 1, and Lactobacillus helveticus 611. A broad spectrum of antibacterial and antifungal activity was determined. The strain-specific inhibition of Staphylococcus aureus, Streptococcus mutans, Escherichia coli, Pseudomonas aeruginosa, and saprophytic/toxigenic fungi makes them promising as protective cultures. DPPH (2,2-diphenyl-1-picrylhydrazyl) and ABTS (2,2′-azino-bis-(3-ethylbenzothiazoline-6-sulfonic) acid) measurements showed that tested samples had strain-specific capacity for scavenging of radicals. The molecular base for the antioxidant potential of two lyophilized forms of active strains was investigated by electron paramagnetic resonance spectroscopy. The MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, with fractions of the most active postbiotics obtained by SEC-FPLC (fast protein liquid chromatography) analysis, showed a wide variety of effects on the growth of a K562 myeloid leukemia cell line. The IC50 (half-maximal inhibitory concentration) of L. salivarius 1 was determined to be 46.15 mg/mL. The proven in vitro functionality of the selected lactobacilli make them suitable for development of target probiotics with specific beneficial effects expected in vivo. Further investigations on produced postbiotics and safety have to be completed before they can be considered as scientifically proven probiotic strains. [ABSTRACT FROM AUTHOR]

The paper presents the assessment results of the irradiation temperature effect on the change in the type of structural defects caused by irradiation with helium ions in the near-surface layer of Li2ZrO3 ceramics, as well as determining the nature of structural damage using the electron paramagnetic resonance method in the case of irradiation fluence variation. During characterization of the structural changes caused by helium ion irradiation, the main attention was paid to detailing the type of structural defects and radiolysis products arising during irradiation, alongside alterations in their concentration using the electron paramagnetic resonance method. During the experiments, it was determined that the observed effects of thermally stimulated mobility of vacancy defects in the damaged layer caused by irradiation with helium ions indicate a positive effect of thermal heating of samples during irradiation at low fluences. This effect consists in a decline in the number of oxygen vacancies in the damaged layer at low irradiation fluences (1015–1016 cm−2), the concentration of which was determined using the EPR method, and the observed structural changes at low irradiation fluences in the case of an elevation in irradiation temperatures are associated with deformation distortion of the crystalline structure of ceramics caused by transformation energy processes, and thermal expansion effects.

Abstract Crystals of YGa3(BO3)4, YAl3(BO3)4, EuGa3(BO3)4 and EuAl3(BO3)4 with copper alloy were studied by electron paramagnetic resonance and X-ray diffraction analysis. The lattice parameters and coordinates of copper-doped boron atoms were determined. The study of EPR spectra showed that copper is in the divalent state and replaces aluminum ions with C2 node symmetry. In YAl3(BO3)4:Cu crystals, a ligand structure exists due to the interaction of copper electrons with yttrium nuclei. The parameters of the spin Hamiltonian describing the behavior of the Cu2+ spectrum have been determined. The deviation of the Z-axis spectra from the C3 axis by 54(1)° is due to Jahn-Teller vibronic interaction and monoclinic distortion. In the EuGa3(BO3)4 crystal, a new spectrum 2 was found, which also belongs to divalent copper but is observed at an excited state 31 cm−1 away from the ground state. Above 70 K, an isotropic EPR line with a width of 450 Gs, g = 2.1, appears and exists up to room temperature.

The intricate dynamics of antioxidant interactions holds promise for innovating formulations to reduce patient antioxidants doses and prolong efficacy, these aspects being also important for other industrial applications, such as food preservation. In this context, the study presents data on the antioxidant interaction between ascorbic (AA) and dihydroxyfumaric acids (DHF) determined via DPPH method, by applying EPR spectroscopy. Two calculations methods used demonstrated strong and moderate synergistic effects, with antioxidant interaction parameter (AI) of 1.24 and 0.9, respectively. The type of antioxidant interaction is dependent on the concentration ratio of the ascorbic and dihydroxyfumaric acids, thus, at the mM DHF/mM AA ratios of 1.4 and 1.7 the highest synergistic effects with AI of 1.24 have been noticed, but at the mM DHF/mM AA ratio of 1 – an antagonistic effect with AI of 0.93 was registered.

The heme synthase AhbD catalyzes the last step of the siroheme-dependent heme biosynthesis pathway, which is operative in archaea and sulfate-reducing bacteria. The AhbD-catalyzed reaction consists of the oxidative decarboxylation of two propionate side chains of iron-coproporphyrin III to the corresponding vinyl groups of heme b. AhbD is a Radical SAM enzyme employing radical chemistry to achieve the decarboxylation reaction. Previously, it was proposed that the central iron ion of the substrate iron-coproporphyrin III participates in the reaction by enabling electron transfer from the initially formed substrate radical to an iron-sulfur cluster in AhbD. In this study, we investigated the substrate radical that is formed during AhbD catalysis. While the iron-coproporphyrinyl radical was not detected by electron paramagnetic resonance (EPR) spectroscopy, trapping and visualization of the substrate radical was successful by employing substrate analogs such as coproporphyrin III and zinc-coproporphyrin III. The radical signals detected by EPR were analyzed by simulations based on density functional theory (DFT) calculations. The observed radical species on the substrate analogs indicate that hydrogen atom abstraction takes place at the β-position of the propionate side chain and that an electron donating ligand is located in proximity to the central metal ion of the porphyrin. [ABSTRACT FROM AUTHOR]

Oxidative stress is a major source of ROS-mediated damage to macromolecules, tissues, and the whole body. It is an important marker in the severe picture of pathological conditions. The discovery of free radicals in biological systems gives a "start" to studying various pathological processes related to the development and progression of many diseases. From this moment on, the enrichment of knowledge about the participation of free radicals and free-radical processes in the pathogenesis of cardiovascular, neurodegenerative, and endocrine diseases, inflammatory conditions, and infections, including COVID-19, is increasing exponentially. Excessive inflammatory responses and abnormal reactive oxygen species (ROS) levels may disrupt mitochondrial dynamics, increasing the risk of cell damage. In addition, low serum albumin levels and changes in the normal physiological balance between reduced and oxidized albumin can be a serious prerequisite for impaired antioxidant capacity of the body, worsening the condition in patients. This review presents the interrelationship between oxidative stress, inflammation, and low albumin levels, which are hallmarks of COVID-19. [ABSTRACT FROM AUTHOR]

Pulsed electron–electron double resonance (PELDOR) spectroscopy is a powerful method for determining nucleic acid (NA) structure and conformational dynamics. PELDOR with molecular dynamics (MD) simulations opens up unique possibilities for defining the conformational ensembles of flexible, three-dimensional, self-assembled complexes of NA. Understanding the diversity and structure of these complexes is vital for uncovering matrix and regulative biological processes in the human body and artificially influencing them for therapeutic purposes. To explore the reliability of PELDOR and MD simulations, we site-specifically attached nitroxide spin labels to oligonucleotides, which form self-assembled complexes between NA chains and exhibit significant conformational flexibility. The DNA complexes assembled from a pair of oligonucleotides with different linker sizes showed excellent agreement between the distance distributions obtained from PELDOR and calculated from MD simulations, both for the mean inter-spin distance and the distance distribution width. These results prove that PELDOR with MD simulations has significant potential for studying the structure and dynamics of conformational flexible complexes of NA. [ABSTRACT FROM AUTHOR]

Conjugated molecules with multiple radical centers such as the iconic Chichibabin diradicaloid hold promise as building blocks in materials for quantum sensing and quantum information processing. However, it is a considerable challenge to design simple analogues of the Chichibabin hydrocarbon that are chemically inert, exhibit high diradical character and emit light at a distinct wavelength that may offer an optical readout of the spin state in functional ensembles. Here we describe the serendipitous discovery of the stable TTM‐TTM diradicaloid, which exhibits high diradical character, a striking sky‐blue color and near‐infrared (NIR) emission (in solution). This combination of properties is unique among related diradicaloids and is due to the presence of hydrogen and chlorine atoms in "just the right positions", allowing a perfectly planar, yet predominantly benzenoid bridge to connect the two sterically stabilized radical centers. In‐depth studies of the optical and magnetic properties suggest that this structural motif could become a mainstay building block of organic spin materials. [ABSTRACT FROM AUTHOR]

Two diphosphanes with variable-length ligands tested as nucleophiles to prepare isoporphyrin copolymers in the presence of ditolylporphyrin of zinc (ZnT2P) prevented the oxidation of the diphosphine ligand. This paper demonstrates the power of this approach and describes the photoelectrocatalytic properties. The obtained copolymers were characterized by UV–vis spectroscopy, X-ray photoelectron spectroscopy, atomic force micrograph (AFM), EQCM (Electrochemical Quartz Cristal Microbalance) and electrochemistry. Their impedance properties (EIS) were studied and their photovoltaic performances were also investigated by photocurrent transient measurements under visible light irradiation. [ABSTRACT FROM AUTHOR]

Ovalbumin (OVA), a protein vital for chick embryo nutrition, hydration, and antimicrobial protection, together with other egg-white proteins, migrates to the amniotic fluid and is orally absorbed by the embryo during embryogenesis. Recently, it has been shown that for optimal eggshell quality, the hen diet can be supplemented with manganese. Although essential for embryonic development, manganese in excess causes neurotoxicity. This study investigates whether OVA may be involved in the regulation of manganese levels. The binding of Mn(II) to OVA was investigated using electron paramagnetic resonance (EPR) spectroscopy. The results show that OVA binds a maximum of two Mn(II) ions, one with slightly weaker affinity, even in a 10-fold excess, suggesting it may have a protective role from Mn(II) overload. It seems that the binding of Mn(II), or the presence of excess Mn(II), does not affect OVA’s tertiary structure, as evidenced from fluorescence and UV/vis measurements. Comparative analysis with bovine and human serum albumins revealed that they exhibit higher affinities for Mn(II) than OVA, most likely due to their essentially different physiological roles. These findings suggest that OVA does not play a role in the transport and storage of manganese; however, it may be involved in embryo protection from manganese-induced toxicity. [ABSTRACT FROM AUTHOR]

Two new binuclear tetranitrosyl iron complexes of the composition [Fe2L2(NO)4] (1, L = 4-methoxybenzenemethanethiolyl; 2, L = 4-chlorobenzenemethanethiolyl) were synthesized. Their crystals were characterized by X-ray diffraction, by IR, ESR, UV, and Mössbauer spectroscopies, and by elemental analysis. The NO-donating properties and transformations of the complexes in physiological solutions, including reactions in the presence of bovine serum albumin, were studied. The cytotoxicity of compounds 1 and 2 was studied on normal Vero cells. The effect of the complexes on enzymes was investigated taking guanylate cyclase and adenylate cyclase as examples. The results obtained allow one to recommend compound 2 for further investigations as a potential drug with vaso- and bronchodilator properties. [ABSTRACT FROM AUTHOR]

The paper reports the first comprehensive physicochemical study of minerals of the amblygonite LiAlPO4F–montebrasite LiAlPO4(OH) series. An EPR spectroscopic and calorimetric study of montebrasite LiAlPO4(OH)0.9F0.1 from the Shuk-Byul rare-metal granite pegmatites (Sangilen Highlands, Tuva) and amblygonite LiAlPO4F0.5(OH)0.5 from pegmatites of the Voron'i Tundras (Kola Peninsula) was carried out. Using the EPR method, the radiation-sensitive paramagnetic O– centers were discovered. They were formed without participation of impurity elements in the regular sites of crystal lattice. The possibility use of minerals of the amblygonite–montebrasite series for EPR geochronometry has been demonstrated for the first time. Using the method of high-temperature melt dissolution calorimetry on a Tian-Calvét microcalorimeter, the enthalpies of formation from elements (298.15 K) = –2326.3 ± 2.2 kJ/mol for montebrasite with the composition LiAl(PO4)(OH)0.9F0.1 and for amblygonite with the composition LiAl(PO4)F0.5(OH)0.5 (‒2347.9 ± 3.1 kJ/mol) are obtained; and the values of this parameter are calculated for the end members with an ideal composition of the series: for montebrasite (–2315.5 ± 2.2 kJ/mol) and for amblygonite (–2401.6 ± 3.1 kJ/mol). The values of the standard entropy S0 (298.15 K) and the Gibbs energy of formation (298.15 K) for intermediate and end members of the amblygonite–montebrasite series are estimated. [ABSTRACT FROM AUTHOR]

Introduction: Antioxidants protect against free radicals. Objective: The aim of this work is to determine the influence of the composition of the plant raw material on magnitude and kinetics of interactions with free radicals of infusions obtained from a mixture of artichoke (Cynara scolymus L.) herbs and dandelion (Taraxacum officinale) flowers. The composition of a complex plant raw material with strong antioxidative properties was searched. Material and Methods: The infusions were prepared from the mixtures of C. scolymus herbs and T. officinale flowers with weight ratio of the ingredients: 1:1, 2:1, and 1:2. The proportions of the ingredients in the examined mixtures were chosen to obtain the effect of the individual plant components on free radical interactions of the infusions from the complex material. Antioxidant properties were examined by electron paramagnetic resonance (EPR) spectroscopy and the model DPPH free radicals. Results and Discussion: EPR spectra of DPPH free radicals decrease as a result of interactions with the examined plant infusions. The decrease of the EPR spectra was strongest and the weakest for infusions of complex plant raw material with the ratio of ingredients 2:1 and 1:1, respectively. Conclusions: All tested infusions of a mixture of artichoke (C. scolymus) herbs and dandelion (T. officinale) flowers, with ingredient weight ratios of 1:1, 2:1 and 1:2, quench free radicals. The character of kinetics of free radical interactions for the tested infusions are similar. An infusion of complex plant raw material with a 2:1 weight ratio of ingredients has the strongest effect on eliminating free radicals. An infusion with a 1:1 weight ratio of ingredients has the weakest ability to quench free radicals. [ABSTRACT FROM AUTHOR]