Estimating the initial absorbed dose of radiation in dried figs using EPR spectroscopy

Dried figs were studied by Electron Paramagnetic Resonance (EPR) spectroscopy for identification of radiation treatment and dosage assessment. Gamma-irradiated samples show a multicomponent "sugar-like" EPR spectrum with line width of 6-8 mT, centered at g = 2.004. The investigation of the influence of the instrumental parameters microwave power and modulation amplitude on the EPR signal show saturation effect at microwave power above 2 mW and over modulation at modulation amplitude above 0.4 mT. Determination of the stability of radiation induced signals shows, that identification of previous radiation treatment is possible for a long time period after irradiation even more than one year. Dose-response curves of gamma-irradiated samples exhibits a linear response up to about 4 kGy and the saturation of the EPR signal at higher doses. A Single Aliquot Additive dosing method used to estimate the initial absorbed dose in irradiated dried fig flesh shows initial dose 0.25 kGy for the sample irradiated by 5 kGy and 3.7 kGy for those irradiated using 10 kGy. Taking into account the signal decay after 150 days of storage, the dose defined as initial should be 4.65 kGy for the 5 kGy irradiated sample and 8 kGy for that irradiated using 10 kGy.

Spectroscopic and thermal investigations on Zn2+ and Ba2+ ions modified 30TeO2-39.5B2O3-(30-x)ZnO-xBaO-0.5V2O5 (0 ≤ x ≤ 30 mol %) glass system

Melt quenching technique was employed to prepare glasses with compositional formula 30TeO2-39.5B2O3-(30-x)ZnO-xBaO-0.5V2O5 (0 ≤ x ≤ 30 mol%). Various characterization tools viz., X-ray diffraction (XRD), Energy dispersive X-ray (EDX) includes color mapping images, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR), Raman, Differential scanning calorimetry (DSC), UV-Vis absorption and Electron paramagnetic resonance (EPR) were used in this investigation for the characterization of these glasses. The XRD patterns together with DSC thermograms asserted the amorphous nature of all glasses. FTIR and Raman vibrational analyses has unveiled the formation of B-O--Ba2+-O- and Te-O---Ba2+-O- wherein the bonds with Ba2+ ions are mostly ionic. DSC investigations disclosed that the increase of BaO at the cost of ZnO declined the crystal phases and favored the amorphosity and this behavior causes these glasses more advantageous for fiber drawing. The Urbach energy (ΔE) lies in between 0.28 and 0.57 eV and suggested the glasses containing high ZnO has less defects. EPR data validated that Ba2+ ions might surround V4+ ions as Ba2+-O-V4+=O by replacing Zn2+-O-V4+=O linkages. The other optical properties were discussed in detail by correlating the structural variations noticed from both FTIR and Raman data analyses.

Evaluation of gamma irradiation effects on antioxidant capacity of propolis

The irradiation effects on antioxidant potential and on content of phenolic compounds of propolis ethanoic extracts were studied. It was found out that gamma treatment of samples with 2 and 10 kGy had a weak decreasing effect on the total phenolic content (TPC), while no change was observed in the propolis irradiated with 5 kGy. The antiradical activity of extracts was assessed by the DPPH free radical scavenging activity evaluated by Electron Paramagnetic Resonance (EPR) spectroscopy. The EPR results were in agreement with TPC. Some main phenolic compounds of the studied non-irradiated and irradiated samples were identified and compared by ultra-high performance liquid chromatography (UHPLC).

Uptake of vanadium and its intracellular metabolism by Coprinellus truncorum mycelial biomass

BACKGROUND

Fungi absorb and solubilize a broad spectrum of heavy metals such as vanadium (V), which makes them a main route of its entry into the biosphere. V as vanadate (V5+) is a potential medical agent due to its many metabolic actions such as interaction with phosphates in the cell, and especially its insulin-mimetic activity. Antidiabetic activity of V-enriched fungi has been studied in recent years, but the biological and chemical bases of vanadium action and status in fungi in general are poorly understood, with almost no information on edible fungi.

METHODS

This manuscript gives a deeper insight into the interaction of V5+ with Coprinellus truncorum, an edible autochthonous species widely distributed in Europe and North America. Vanadium uptake and accumulation as V5+ was studied by 51V NMR, while the reducing abilities of the mycelium were determined by EPR. 31P NMR was used to determine its effects on the metabolism of phosphate compounds, with particular focus on phosphate sugars identified using HPLC.

RESULTS

Vanadate enters the mycelium in monomeric form and shows no immediate detrimental effects on intracellular pH or polyphosphate (PPc) levels, even when applied at physiologically high concentrations (20 mM Na3VO4). Once absorbed, it is partially reduced to less toxic vanadyl (V4+) with notable unreduced portion, which leads to a large increase in phosphorylated sugar levels, especially glucose-1-phosphate (G1P) and fructose-6-phosphate (F6P).

CONCLUSIONS

Preservation of pH and especially PPc reflects maintenance of the energy status of the mycelium, i.e., its tolerance to high V5+ concentrations. Rise in G1P and F6P levels implies that the main targets of V5+ are most likely phosphoglucomutase and phosphoglucokinase(s), enzymes involved in early stages of G6P transformation in glycolysis and glycogen metabolism. This study recommends C. truncorum for further investigation as a potential antidiabetic agent.

Disentangling the intrinsic relaxivities of highly purified graphene oxide

The chemistry of contrast agents (CAs) for magnetic resonance imaging (MRI) applications is an active area of research and, in recent work, it was shown that CA-based graphene oxide (GO) has valuable properties for biomedical uses. GO has a potential as MRI CAs thanks to several functionalities, like its ability to penetrate tissues and cell membranes, as well as easy coupling with therapeutic agents, therefore showing the potential for both a diagnostic and therapeutic role. In this study, we performed a thorough cleaning of the GO sample (synthesized using a modified Hummers method), minimizing the amount of residual manganese down to 73 ppm. Using a wide range of physical-chemical methods (morphology, chemical composition, elemental analysis, spectroscopies, and imaging), we characterized the intrinsic longitudinal and transverse relaxivities of highly purified GO nanosheets. X-band electron paramagnetic resonance allowed to recognize the paramagnetic species involved, and 1.0 T MRI was used to disentangle the relative contributions to the MRI contrast of pristine GO nanosheets arising from structural defects and residual paramagnetic manganese impurities embedded in the nanomaterial. Although experiments show that the MRI relaxivity of GO nanosheets arises from the cumulative effect of structural defects and paramagnetic impurities, we conclude that the latter contribution to the longitudinal and transverse relaxivities becomes irrelevant for highly purified (pristine) GO. This novel finding clearly demonstrates that, apart from trivial manganese inclusion, pristine GO produces an inherent MRI response via structural defects, and therefore it is on its own a suitable candidate as MRI contrast agent.

Structure and Photophysics of N-Tolanyl-phenochalcogenazines and their Radical Cations

The study focuses on the structural and photophysical characteristics of neutral and oxidized forms of N-tolanyl-phenochalcogenazines PZX-tolan with X=O, S, Se, and Te. X-ray crystal structure analyses show a pseudo-equatorial (pe) structure of the tolan substituent in the O, S, and Se dyads, while the Te dyad possesses a pseudo-axial (pa) structure. DFT calculations suggest the pe structure for O and S, and the pa structure for Se and Te as stable forms. Steady-state and femtosecond-time resolved optical spectroscopy in toluene solution indicate that the O and S dyads emit from a CT state, whereas the Se and Te dyads emit from a tolan-localized state. The T1 state is tolan-localized in all cases, showing phosphorescence at 77 K. The heavy atom effect of chalcogens induces intersystem crossing from S1 to Tx, resulting in a decreasing S1 lifetime from 2.1 ns to 0.42 ps. The T1 states possess potential for singlet oxygen sensitization with a high quantum yield (ca. 40 %) for the O, S, and Se dyads. Radical cations exhibit spin density primarily localized at the heterocycle. EPR measurements and quasirelativistic DFT calculations reveal a very strong g-tensor anisotropy, supporting the pe structure for the S and Se derivatives.

Revealing the nuclearity of iron citrate complexes at biologically relevant conditions

Citric acid plays an ubiquitous role in the complexation of essential metals like iron and thus it has a key function making them biologically available. For this, iron(III) citrate complexes are considered among the most significant coordinated forms of ferric iron that take place in biochemical processes of all living organisms. Although these systems hold great biological relevance, their coordination chemistry has not been fully elucidated yet. The current study aimed to investigate the speciation of iron(III) citrate using Mössbauer and electron paramagnetic resonance spectroscopies. Our aim was to gain insights into the structure and nuclearity of the complexes depending on the pH and iron to citrate ratio. By applying the frozen solution technique, the results obtained directly reflect the iron speciation present in the aqueous solution. At 1:1 iron:citrate molar ratio, polynuclear species prevailed forming most probably a trinuclear structure. In the case of citrate excess, the coexistence of several monoiron species with different coordination environments was confirmed. The stability of the polynuclear complexes was checked in the presence of organic solvents.

Interaction with CT-DNA and in vitro cytotoxicity of two new copper(II)-based potential drugs derived from octanoic hydrazide ligands

Two copper(II) complexes [Cu(Hpmoh)(NO3)(NCS)] (1) and [Cu(peoh)(N3)]2 (2) were designed and synthesized by reaction of Cu(NO3)2·3H2O with hydrazone Schiff base ligands,abbreviated with Hpmoh and Hpeoh. Hpmoh and Hpeoh were prepared by condensation reaction of octanoic hydrazide with pyridine-2-carboxyaldehyde and 2-acetylpyridine, respectively. Complexes 1 and 2 were characterized using different analytical techniques such as FT-IR, UV-Vis, IR, EPR and single X-ray diffraction (XRD) analyses as well as computational methods (DFT). The XRD of 1 and 2 shows a mononuclear or a dinuclear structure with the copper(II) centre adopting a slightly distorted square pyramidal geometry. In water-containing solution and in DMSO, 1 and 2 undergo a partial transformation with formation of [Cu(Hpmoh)(NO3)(NCS)] (1) and [Cu(Hpmoh)(NO3)(H2O/DMSO)] (1a) in one system and [Cu(peoh)(N3)] (2a) in the other one, as supported by DFT calculations. Docking simulations confirmed that the intercalation is the preferred binding mode with DNA for 1, 1a and 2a, but suggested that the minor groove binding is also possible. A significant fluorescence quenching of the DNA-ethidium bromide conjugate was observed upon the addition of complexes 1 and 2 with a quenching constant around 104 M-1 s-1. Finally, both 1 and 2 were examined for anti-cancer activity using MDA-MB-231 (human breast adenocarcinoma) and A375 (malignant melanoma) cell lines through in vitro MTT assay which suggest comparable cancer cell killing efficacy, with the higher effectiveness of 2 due to the dissociation into two [Cu(peoh)(N3)] units.

Superoxide Radicals in Uranyl Peroxide Solids: Lasting Signatures Identified by Electron Paramagnetic Resonance Spectroscopy

U(VI) peroxide phases (studtite and meta-studtite) are found throughout the nuclear fuel cycle and exist as corrosion products in high radiation fields. Peroxides are part of a family of reactive oxygen species (ROS) that include hydroperoxyl and superoxide species and are produced during alpha radiolysis of water. While U(VI) peroxides have been thoroughly investigated, the incorporation and stability of ROS species within studtite have not been validated. In the current study, electron paramagnetic resonance (EPR) spectroscopy was used to identify the presence of free radicals within a series of U(VI) peroxide samples containing depleted, highly enriched, and natural uranium. Density functional theory calculations indicated that the predicted EPR signals matched well with a superoxide (O2 -⋅) species incorporated into the studtite structure, confirming the presence of ROS in the material. Further analysis of samples that were synthesized between 1945 and 2023 indicated that there is a correlation between the radical signal and the product of specific activity multiplied by age of the sample.

Highly Sensitive Detection of Melanin in Melanomas Using Multi-harmonic Low Frequency EPR

PURPOSE

Low frequency EPR can noninvasively detect endogenous free radical melanin in melanocytic skin lesions and could potentially discriminate between benign atypical nevi and malignant melanoma lesions. We recently succeeded in demonstrating the ability of clinical EPR to noninvasively detect the endogenous melanin free radical in skin lesions of patients. However, the signal-to-noise ratio (SNR) was extremely low warranting further research to boost the sensitivity of detection. In the present study, we assessed the performance of a clinical EPR system with the capability to perform multi-harmonic (MH) analysis for the detection of melanin.

PROCEDURES

The sensitivity of MH-EPR was compared with a classical continuous wave (CW)-EPR (1st harmonic) detection in vitro in melanin phantoms, in vivo in melanoma models with cells implanted in the skin, in lymph nodes and having colonized the lungs, and finally on phantoms placed at the surface of human skin.

RESULTS

In vitro, we observed an increase in SNR by a factor of 10 in flat melanin phantoms when using MH analysis compared to CW combined with an increase in modulation amplitude. In B16 melanomas having grown in the skin of hairless mice, we observed a boost in sensitivity in vivo similar to that observed in vitro with the capability to detect melanoma cells at an earlier stage of development. MH-EPR was also able to detect non-invasively the melanin signal coming from melanoma cells present in lymph nodes as well as in lungs. We also observed a boost of sensitivity using phantoms of melanin placed at the surface of human skin.

CONCLUSIONS

Overall, our results are paving the way for new clinical trials that will use MH clinical EPR for the characterization of pigmented skin lesions.

Monitoring the conformational ensemble and lipid environment of a mechanosensitive channel under cyclodextrin-induced membrane tension

Membrane forces shift the equilibria of mechanosensitive channels enabling them to convert mechanical cues into electrical signals. Molecular tools to stabilize and methods to capture their highly dynamic states are lacking. Cyclodextrins can mimic tension through the sequestering of lipids from membranes. Here we probe the conformational ensemble of MscS by EPR spectroscopy, the lipid environment with NMR, and function with electrophysiology under cyclodextrin-induced tension. We show the extent of MscS activation depends on the cyclodextrin-to-lipid ratio, and that lipids are depleted slower when MscS is present. This has implications in MscS' activation kinetics when distinct membrane scaffolds such as nanodiscs or liposomes are used. We find MscS transits from closed to sub-conducting state(s) before it desensitizes, due to the lack of lipid availability in its vicinity required for closure. Our approach allows for monitoring tension-sensitive states in membrane proteins and screening molecules capable of inducing molecular tension in bilayers.

Structural transitions modulate the chaperone activities of Grp94

Hsp90s are ATP-dependent chaperones that collaborate with co-chaperones and Hsp70s to remodel client proteins. Grp94 is the ER Hsp90 homolog essential for folding multiple secretory and membrane proteins. Grp94 interacts with the ER Hsp70, BiP, although the collaboration of the ER chaperones in protein remodeling is not well understood. Grp94 undergoes large-scale conformational changes that are coupled to chaperone activity. Within Grp94, a region called the pre-N domain suppresses ATP hydrolysis and conformational transitions to the active chaperone conformation. In this work, we combined in vivo and in vitro functional assays and structural studies to characterize the chaperone mechanism of Grp94. We show that Grp94 directly collaborates with the BiP chaperone system to fold clients. Grp94's pre-N domain is not necessary for Grp94-client interactions. The folding of some Grp94 clients does not require direct interactions between Grp94 and BiP in vivo, suggesting that the canonical collaboration may not be a general chaperone mechanism for Grp94. The BiP co-chaperone DnaJB11 promotes the interaction between Grp94 and BiP, relieving the pre-N domain suppression of Grp94's ATP hydrolysis activity. In structural studies, we find that ATP binding by Grp94 alters the ATP lid conformation, while BiP binding stabilizes a partially closed Grp94 intermediate. Together, BiP and ATP push Grp94 into the active closed conformation for client folding. We also find that nucleotide binding reduces Grp94's affinity for clients, which is important for productive client folding. Alteration of client affinity by nucleotide binding may be a conserved chaperone mechanism for a subset of ER chaperones.

Exploring the Effect of V2O5 and Nb2O5 Content on the Structural, Thermal, and Electrical Characteristics of Sodium Phosphate Glasses and Glass-Ceramics

Na-V-P-Nb-based materials have gained substantial recognition as cathode materials in high-rate sodium-ion batteries due to their unique properties and compositions, comprising both alkali and transition metal ions, which allow them to exhibit a mixed ionic-polaronic conduction mechanism. In this study, the impact of introducing two transition metal oxides, V2O5 and Nb2O5, on the thermal, (micro)structural, and electrical properties of the 35Na2O-25V2O5-(40 - x)P2O5 - xNb2O5 system is examined. The starting glass shows the highest values of DC conductivity, σDC, reaching 1.45 × 10-8 Ω-1 cm-1 at 303 K, along with a glass transition temperature, Tg, of 371 °C. The incorporation of Nb2O5 influences both σDC and Tg, resulting in non-linear trends, with the lowest values observed for the glass with x = 20 mol%. Electron paramagnetic resonance measurements and vibrational spectroscopy results suggest that the observed non-monotonic trend in σDC arises from a diminishing contribution of polaronic conductivity due to the decrease in the relative number of V4+ ions and the introduction of Nb2O5, which disrupts the predominantly mixed vanadate-phosphate network within the starting glasses, consequently impeding polaronic transport. The mechanism of electrical transport is investigated using the model-free Summerfield scaling procedure, revealing the presence of mixed ionic-polaronic conductivity in glasses where x < 10 mol%, whereas for x ≥ 10 mol%, the ionic conductivity mechanism becomes prominent. To assess the impact of the V2O5 content on the electrical transport mechanism, a comparative analysis of two analogue series with varying V2O5 content (10 and 25 mol%) is conducted to evaluate the extent of its polaronic contribution.

An Isolable One-Coordinate Lead(I) Radical with Strong g-Factor Anisotropy

Lead-based radicals in the oxidation state of +1 are elusive species and are highly challenging to isolate in the condensed phase. In this study, we present the synthesis and characterization of the first isolable free plumbylyne radical 2 bearing a one-coordinate Pb(I) atom. It reacts with an N-heterocyclic carbene (NHC) to afford a two-coordinate NHC-ligated Pb(I) radical 3. 2 and 3 represent the first isolable Pb(I)-based radicals. Theoretical calculations and electron paramagnetic resonance analysis revealed that the unpaired electron mainly resides at the Pb 6p orbital in both radicals. Owing to the unique one-coordinate nature of the Pb atom in 2, it possesses two-fold orbital pseudo-degeneracy and substantial unquenched orbital angular momentum, and exhibits hitherto strongest g-factor anisotropy (gx,y,z=1.496, 1.166, 0.683) amongst main group radicals. Preliminary investigations into the reactivity of 2 unveiled its Pb-centered radical nature, and plumbylenes were isolated as products.

Using imaging modalities to predict nanoparticle distribution and treatment efficacy in solid tumors: The growing role of ultrasound

Nanomedicine in oncology has not had the success in clinical impact that was anticipated in the early stages of the field's development. Ideally, nanomedicines selectively accumulate in tumor tissue and reduce systemic side effects compared to traditional chemotherapeutics. However, this has been more successful in preclinical animal models than in humans. The causes of this failure to translate may be related to the intra- and inter-patient heterogeneity of the tumor microenvironment. Predicting whether a patient will respond positively to treatment prior to its initiation, through evaluation of characteristics like nanoparticle extravasation and retention potential in the tumor, may be a way to improve nanomedicine success rate. While there are many potential strategies to accomplish this, prediction and patient stratification via noninvasive medical imaging may be the most efficient and specific strategy. There have been some preclinical and clinical advances in this area using MRI, CT, PET, and other modalities. An alternative approach that has not been studied as extensively is biomedical ultrasound, including techniques such as multiparametric contrast-enhanced ultrasound (mpCEUS), doppler, elastography, and super-resolution processing. Ultrasound is safe, inexpensive, noninvasive, and capable of imaging the entire tumor with high temporal and spatial resolution. In this work, we summarize the in vivo imaging tools that have been used to predict nanoparticle distribution and treatment efficacy in oncology. We emphasize ultrasound imaging and the recent developments in the field concerning CEUS. The successful implementation of an imaging strategy for prediction of nanoparticle accumulation in tumors could lead to increased clinical translation of nanomedicines, and subsequently, improved patient outcomes. This article is categorized under: Diagnostic Tools In Vivo Nanodiagnostics and Imaging Therapeutic Approaches and Drug Discovery Nanomedicine for Oncologic Disease Therapeutic Approaches and Drug Discovery Emerging Technologies.

Sensitive simultaneous measurements of oxygenation and extracellular pH by EPR using a stable monophosphonated trityl radical and lithium phthalocyanine

The monitoring of acidosis and hypoxia is crucial because both factors promote cancer progression and impact the efficacy of anti-cancer treatments. A phosphonated tetrathiatriarylmethyl (pTAM) has been previously described to monitor both parameters simultaneously, but the sensitivity to tackle subtle changes in oxygenation was limited. Here, we describe an innovative approach combining the pTAM radical and lithium phthalocyanine (LiPc) crystals to provide sensitive simultaneous measurements of extracellular pH (pHe) and pO2. Both parameters can be measured simultaneously as both EPR spectra do not overlap, with a gain in sensitivity to pO2 variations by a factor of 10. This procedure was applied to characterize the impact of carbogen breathing in a breast cancer 4T1 model as a proof-of-concept. No significant change in pHe and pO2 was observed using pTAM alone, while LiPc detected a significant increase in tumor oxygenation. Interestingly, we observed that pTAM systematically overestimated the pO2 compared to LiPc. In addition, we analyzed the impact of an inhibitor (UK-5099) of the mitochondrial pyruvate carrier (MPC) on the tumor microenvironment. In vitro, the exposure of 4T1 cells to UK-5099 for 24 h induced a decrease in pHe and oxygen consumption rate (OCR). In vivo, a significant decrease in tumor pHe was observed in UK-5099-treated mice, while there was no change for mice treated with the vehicle. Despite the change observed in OCR, no significant change in tumor oxygenation was observed after the UK-5099 treatment. This approach is promising for assessing in vivo the effect of treatments targeting tumor metabolism.

Peculiarities of charge compensation in lithium-doped hydroxyapatite

Hydroxyapatite (HA) remains one of the most popular materials for various biomedical applications and its fields of application have been expanding. Lithium (Li+) is a promising candidate for modifying the biological behavior of HA. Li+ is present in trace amounts in the human body as an alkaline and bioelectric material. At the same time, the introduction of Li+ into the HA structure required charge balance compensation due to the difference in oxidation degree, and the scheme of this compensation is still an open question. In the present work, the results of the theoretical and experimental study of the Li+-doped HA synthesis are presented. According to X-ray diffraction data, Fourier transform infrared spectroscopy as well as the combination of electron paramagnetic resonance methods, the introduction of Li+ in the amount up to 0.05 mol% resulted in the preservation of the HA structure. Density functional theory calculations show that Li+ preferentially incorporates into the Ca (1) position with a small geometry perturbation. The less probable positioning in the Ca (2) position leads to a drastic perturbation of the anion channel.

Identification of paramagnetic centers in irradiated Sn-doped silicon dioxide by first-principles

We present a first-principles investigation of Sn paramagnetic centers in Sn-doped vitreous silica based on calculations of the electron paramagnetic resonance (EPR) parameters. The present investigation provides evidence of an extended analogy between the family of Ge paramagnetic centers in Ge-doped silica and the family of Sn paramagnetic centers in Sn-doped silica for SnO2concentrations below phase separation. We infer, also keeping into account the larger spin-orbit coupling of Sn atoms with respect to Ge atoms, that a peculiar and highly distorted three-fold coordinated Sn center (i.e. the Sn forward-oriented configuration) should give rise to an orthorhombic EPR signal of which we suggest a fingerprint in the EPR spectra recorded by Chiodiniet al(2001Phys. Rev.B64073102). Given its structural analogy with theEα'and Ge(2) centers, we here name it as the 'Sn(2) center'. Moreover, we show that the single trapped electron at a SnO4tetrahedron constitutes a paramagnetic center responsible for the orthorhombic EPR signal reported in Chiodiniet al(1998Phys. Rev.B589615), confuting the early assignment to a distorted variant of the Sn-E' center. We hence relabel the latter orthorhombic EPR signal as the 'Sn(1) center' due to its analogy to the Ge(1) center in Ge-doped silica.

Synthesis and dark state EPR properties of PDI-trityl dyads and triads

Covalently-linked chromophore-radical systems with their unique optical and magnetic properties are useful for applications in, e. g., quantum information science. To expand the catalog of molecular systems, we synthesized and characterized six novel chromophore-radical and radical-chromophore-radical systems employing derivatives of perylene diimide (PDI) as the chromophore and trityl as the radical. The EPR properties of these compounds were evaluated in solution at cryogenic and room temperatures. In addition, the electron spin-spin coupling in the two bistrityl systems was investigated using DQC measurements. The presented results serve as a basis for further spectroscopic investigations under photoexcitation of the PDI core.

Natural Polymorphisms D60E and I62V Stabilize a Closed Conformation in HIV-1 Protease in the Absence of an Inhibitor or Substrate

HIV infection remains a global health issue plagued by drug resistance and virological failure. Natural polymorphisms (NPs) contained within several African and Brazilian protease (PR) variants have been shown to induce a conformational landscape of more closed conformations compared to the sequence of subtype B prevalent in North America and Western Europe. Here we demonstrate through experimental pulsed EPR distance measurements and molecular dynamic (MD) simulations that the two common NPs D60E and I62V found within subtypes F and H can induce a closed conformation when introduced into HIV-1PR subtype B. Specifically, D60E alters the conformation in subtype B through the formation of a salt bridge with residue K43 contained within the nexus between the flap and hinge region of the HIV-1 PR fold. On the other hand, I62V modulates the packing of the hydrophobic cluster of the cantilever and fulcrum, also resulting in a more closed conformation.

Investigation on chain segment motions of various starch molecules under different glycerol-water system

The molecular motion of starch at different glycerol concentrations (0, 20, 50, and 80 %) was investigated using Electron Paramagnetic Resonance (EPR) spectroscopy. Fourier-transform infrared (FTIR) spectroscopy and 1H nuclear magnetic resonance (1H NMR) spectroscopy confirmed that hydroxyl groups at the C2 and C3 positions of glucose units in corn starch (CS), waxy corn starch (WCS), and high amylose corn starch (HCS) were labeled with 4-amino-TEMPO. The crystallinities of CS, WCS, and HCS after spin-labeling decreased from 30.68 % to 3.21 %, 39.36 % to 1.65 %, and 28.54 % to 8.08 %, respectively. The pseudoplastic fluid properties of the spin-labeled starch remained shear-thin at different glycerol concentrations. EPR revealed the fast- and slow-motion components of the spin-labeled starch molecules dispersed in water. At a glycerol concentration of 20 %, the slow-motion component disappeared, indicating a faster rotational motion of the starch chain segments. As the glycerol concentration increased to 50 and 80 %, the rotational motion slowed because of high viscosity. In particular, the mobility of the spin-labeled WCS chains increased owing to easier access of glycerol and water to the branched structure. This study directly observed the dynamics of the molecular behavior of starch in glycerol-water systems.

Hydrophilic Reduction-Resistant Spin Labels of Pyrrolidine and Pyrroline Series from 3,4-Bis-hydroxymethyl-2,2,5,5-tetraethylpyrrolidine-1-oxyl

Highly resistant to reduction nitroxides open new opportunities for structural studies of biological macromolecules in their native environment inside living cells and for functional imaging of pH and thiols, enzymatic activity and redox status in living animals. 3,4-Disubstituted nitroxides of 2,2,5,5-tetraethylpyrrolidine and pyrroline series with a functional group for binding to biomolecules and a polar moiety for higher solubility in water and for more rigid attachment via additional coordination to polar sites were designed and synthesized. The EPR spectra, lipophilicities, kinetics of the reduction in ascorbate-containing systems and the decay rates in liver homogenates were measured. The EPR spectra of all 3,4-disubstituted pyrrolidine nitroxides showed additional large splitting on methylene hydrogens of the ethyl groups, while the spectra of similar pyrroline nitroxides were represented with a simple triplet with narrow lines and hyperfine structure of the nitrogen manifolds resolved in oxygen-free conditions. Both pyrrolidine and pyrroline nitroxides demonstrated low rates of reduction with ascorbate, pyrrolidines being a bit more stable than similar pyrrolines. The decay of positively charged nitroxides in the rat liver homogenate was faster than that of neutral and negatively charged radicals, with lipophilicity, rate of reduction with ascorbate and the ring type playing minor role. The EPR spectra of N,N-dimethyl-3,4-bis-(aminomethyl)-2,2,5,5-tetraethylpyrrolidine-1-oxyl showed dependence on pH with pKa = 3, ΔaN = 0.055 mT and ΔaH = 0.075 mT.

2,5-Di-tert-butyl-2,5-diethylpyrrolidine-1-oxyls: Where Is a Reasonable Limit of Sterical Loading for Higher Resistance to Reduction?

The pyrrolidine nitroxides with four bulky alkyl substituents adjacent to the N-O∙ group demonstrate very high resistance to reduction with biogenic antioxidants and enzymatic systems. This makes them valuable molecular tools for studying the structure and functions of biomolecules directly in a living cell and for functional EPR and NMR tomography in vivo. The first example of highly strained pyrrolidine nitroxides with both ethyl and tert-butyl groups at each of the α-carbon atoms of the nitroxide moiety with cis-configuration of the tert-butyl groups was prepared using a three-component domino reaction of tert-leucine and 2,2-dimethylpentan-3-one with dimethyl fumarate with subsequent conversion of the resulting strained pyrrolidine into 1-pyrroline-1-oxide and addition of EtLi. The nitroxide has demonstrated unexpectedly fast reduction with ascorbate, the rate constant k2 = (2.0 ± 0.1) × 10-3 M-1s-1. This effect was explained by destabilization of the planar nitroxide moiety due to repulsion with the two neighboring tert-butyl groups cis to each other.

Demography, common disorders and mortality of Shih Tzu dogs under primary veterinary care in the UK

BACKGROUND

Shih Tzus are a popular dog breed in the UK although there is relatively little reported information on their health. This study aimed to characterise the demography, common disorders and mortality of Shih Tzus under primary veterinary care during 2016 in the UK using de-identified clinical records from the VetCompass™ Programme.

RESULTS

The study population of 336,865 dogs under veterinary care during 2016 included 11,082 Shih Tzus (3.3%). The median age was 4.1 years (IQR: 2.1-7.1, range: 0.3-20.4) and mean adult bodyweight was 7.9 kg (SD: 1.9 kg). Annual proportional births increased from 2.2% of all dog births in 2005 to 3.8% in 2013, dropping to 3.3% by 2016. From a random subset of 2,423 Shih Tzus that had information extracted on disorders diagnosed during 2016, the most prevalent fine-level precision disorders were periodontal disease (n = 229, prevalence 9.5%, 95% CI: 8.4-10.7), anal sac impaction (180, 7.4%, 95% CI: 6.5-8.5) and ear disorders (134, 5.5%, 95% CI: 4.7-6.5). The most prevalent grouped-level precision disorders were cutaneous (n = 402, prevalence: 16.6%, 95% CI: 15.2-18.1), dental (322, 13.3%, 95% CI: 12.0-14.7), and ophthalmological (289, 11.9%, 95% CI: 10.7-13.3). Males were more likely than females to be diagnosed with skin disorders (P = 0.007) and musculoskeletal disorders (P = 0.010) while females were more likely than males to be diagnosed with hernias (P = 0.005). The median age of death was 12.7 years (IQR 8.7-14.3, range 2.0-19.9) and did not differ statistically between males and females. The most common grouped causes of death were enteropathy (7.9%, 95% CI: 3.9-15.4), heart disease (7.9%, 95% CI: 3.9-15.4) and poor quality of life (7.9%, 95% CI: 3.9-15.4).

CONCLUSIONS

Periodontal disease, anal sac impaction and ear disorders were identified as common health issues. Shih Tzus had higher prevalence of anal sac impaction, umbilical hernias and eye problems than reported previously in dogs overall, suggesting potential predispositions. Shih Tzus appear to be relatively long-lived compared to previous reports of lifespan in dogs overall. The results can inform veterinarians and owners on priority disorders for monitoring to protect welfare. Oral hygiene was highlighted as a healthcare priority.

English Cocker Spaniels under primary veterinary care in the UK: disorder predispositions and protections

BACKGROUND

The English Cocker Spaniel (ECS) is one of the most popular dog breeds in the UK but information on disorder predisposition and protection is limited. Using anonymised veterinary clinical data from the VetCompass™ Programme, this study aimed to compare disorder predisposition and protection between the ECS and the remaining dogs under primary veterinary care in the UK during 2016. Electronic patient records for random samples of ECS and non-ECS were reviewed. The most common disorders diagnosed during 2016 were extracted and compared using multivariable logistic regression, controlling for confounders.

RESULTS

The analysis included random samples of 2510/10,313 (24.3%) ECS and 7813/326,552 (2.39%) non-ECS. After accounting for confounding by age, sex, bodyweight within breed-sex, insurance status and veterinary practice group, the ECS had increased odds of 21/43 (48.85%) disorders at fine-level precision, with highest odds for aural discharge (odds ratio (OR) 14.66, 95% confidence interval (CI): 7.73-30.90, P <  0.001) and keratoconjunctivitis sicca (OR 7.64, 95% CI: 4.33-14.14, P <  0.001) and lowest odds for atopic dermatitis (OR 0.14, 95% CI: 0.05-0.31, P <  0.001) and allergy (OR 0.14, 95% CI: 0.06-0.28, P <  0.001).

CONCLUSIONS

This study provides evidence for strong predisposition to aural and ocular disorders and protection from hypersensitivity disorders in the ECS. These results can aid dog owners, breeders, and veterinarians to better monitor health in ECS, and promote earlier diagnosis with improved prognosis. Further, the results can help breeding organisations establish key priorities the health-based reforms of the ECS.

Effects of intramolecular hydrogen bonding on nuclear magnetic resonance, electron paramagnetic resonance and molecular docking studies: Mexiletine molecule

CONTEXT

In this study, the molecular structure of the mexiletine molecule was investigated. Since the Mexiletine molecule is a drug active ingredient, its molecular structure and spectroscopic properties are important. The effects of intramolecular hydrogen bonding on Nuclear Magnetic Resonance Parameters (NMR), Electron Paramagnetic Resonance (EPR) parameters and molecular docking studies were examined in the mexiletine molecule. The effects of intramolecular hydrogen bonding on EPR parameters and molecular docking studies are the most important steps for this study.

METHOD

Conformational space scanning required for molecular structure calculations was carried out with the Molecular Mechanic Force Field method. DFT method with 6-311 +  + G(d,p) basis set level was used to obtain the most stable structure among the conformations. NMR parameters (1H and 13C chemical shift values) were also performed using the same basis set as the DFT method. The radicals created to calculate the Electron Paramagnetic Resonance parameters were modeled using the DFT/B3LYP/6-311 +  + G(d,p) method basis set level. Molecular Docking studies were carried out with the Autodock vina program.

Experimental and DFT Study of Monensinate and Salinomycinate Complexes Containing {Fe3(µ3-O)}7+ Core

Two trinuclear oxo-centred iron(III) coordination compounds of monensic and salinomycinic acids (HL) were synthesized and their spectral properties were studied using physicochemical/thermal methods (FT-IR, TG-DTA, TG-MS, EPR, Mössbauer spectroscopy, powder XRD) and elemental analysis. The data suggested the formation of [Fe3(µ3-O)L3(OH)4] and the probable complex structures were modelled using the DFT method. The computed spectral parameters of the optimized constructs were compared to the experimentally measured ones. In each complex, three metal centres were joined together at the axial position by a μ3-O unit to form a {Fe3O}7+ core. The antibiotics monoanions served as bidentate ligands through the carboxylate and hydroxyl groups located at the termini. The carboxylate moieties played a dual role bridging each two metal centres. Hydroxide anions secured the overall neutral character of the coordination species. Mössbauer spectra displayed asymmetric quadrupole doublets that were consistent with the existence of two types of high-spin iron(III) sites with different environments-two Fe[O5] and one Fe[O6] centres. The solid-state EPR studies confirmed the +3 oxidation state of iron with a total spin St = 5/2 per trinuclear cluster. The studied complexes are the first iron(III) coordination compounds of monensin and salinomycin reported so far.

Free Radical Inhibition Using a Water-Soluble Curcumin Complex, NDS27: Mechanism Study Using EPR, Chemiluminescence, and Docking

There is a growing interest in the use of natural compounds to tackle inflammatory diseases and cancers. However, most of them face the bioavailability and solubility challenges to reaching cellular compartments and exert their potential biological effects. Polyphenols belong to that class of molecules, and numerous efforts have been made to improve and overcome these problems. Curcumin is widely studied for its antioxidant and anti-inflammatory properties as well as its use as an anticancer agent. However, its poor solubility and bioavailability are often a source of concern with disappointing or unexpected results in cellular models or in vivo, which limits the clinical use of curcumin as such. Beside nanoparticles and liposomes, cyclodextrins are one of the best candidates to improve the solubility of these molecules. We have used lysine and cyclodextrin to form a water-soluble curcumin complex, named NDS27, in which potential anti-inflammatory effects were demonstrated in cellular and in vivo models. Herein, we investigated for the first time its direct free radicals scavenging activity on DPPH/ABTS assays as well as on hydroxyl, superoxide anion, and peroxyl radical species. The ability of NDS27 to quench singlet oxygen, produced by rose bengal photosensitization, was studied, as was the inhibiting effect on the enzyme-catalyzed oxidation of the co-substrate, luminol analog (L012), using horseradish peroxidase (HRP)/hydrogen peroxide (H2O2) system. Finally, docking was performed to study the behavior of NDS27 in the active site of the peroxidase enzyme.

Structural aspects of RimP binding on small ribosomal subunit from Staphylococcus aureus

Ribosome biogenesis is an energy-intense multistep process where even minimal defects can cause severe phenotypes up to cell death. Ribosome assembly is facilitated by biogenesis factors such as ribosome assembly factors. These proteins facilitate the interaction of ribosomal proteins with rRNA and correct rRNA folding. One of these maturation factors is RimP which is required for efficient 16S rRNA processing and 30S ribosomal subunit assembly. Here, we describe the binding mode of Staphylococcus aureus RimP to the small ribosomal subunit and present a 4.2 Å resolution cryo-EM reconstruction of the 30S-RimP complex. Together with the solution structure of RimP solved by NMR spectroscopy and RimP-uS12 complex analysis by EPR, DEER, and SAXS approaches, we show the specificity of RimP binding to the 30S subunit from S. aureus. We believe the results presented in this work will contribute to the understanding of the RimP role in the ribosome assembly mechanism.

Re-examining What the Results of "a Measurement of Oxygen Level in Tissues" Really Mean

Within this special issue, many eminent investigators report on measurements of oxygen (O2) levels in tissues. Given the complexities of spatial and temporal heterogeneities of O2 in tissues and its many sources, this commentary draws attention to what such measurements do and do not actually assess regarding O2 levels in tissues. Given this limitation, it also discusses how these results can be used most effectively. To provide a convenient mechanism to discuss these issues more fully, this analysis focuses on measurements using EPR oximetry, but these considerations apply to all other techniques. The nature of the delivery of O2 to tissues and the mechanisms by which O2 is consumed necessarily result in very different levels of O2 within the volume of each voxel of a measurement. Better spatial resolution cannot fully resolve the problem because the variations include O2 gradients within each cell. Improved resolution of the time-dependent variation in O2 is also very challenging because O2 levels within tissues can have fluctuations of O2 levels in the range of milliseconds, while most methods require longer times to acquire the data from each voxel. Based on these issues, we argue that the values obtained inevitably are complex aggregates of averages of O2 levels across space and time in the tissue. These complexities arise from the complex physiology of tissues and are compounded by the limitations of the technique and its ability to acquire data. However, one often can obtain very meaningful and useful results if these complexities and limitations are taken into account. We illustrate this, using results obtained with in vivo EPR oximetry, especially utilizing its capacity to make repeated measurements to follow changes in O2 levels that occur with interventions and/or over time.

Short communication: Ascorbyl/ascorbate ratio as a marker of oxidative stress in larvae (Apis mellifera) exposed to Paenibacillus larvae

Paenibacillus larvae, the causal agent of American foulbrood disease (AFB), affects Apis mellifera larvae and can induce oxidative stress by overproduction of radical oxygen species (ROS). This study aimed to assess the oxidative stress levels in larvae exposed to three different strains of P. larvae through their diet by examining the ascorbyl radical (A) to ascorbate anion (AH¯) ratio. The results revealed that larvae inoculated with P. larvae exhibited a lower value of this index compared to uninoculated ones. Interestingly, the level of A remained constant, while the concentration of AH¯ increased. Said increase correlated with the virulence of the specific P. larvae strain used in the inoculation. These findings suggest a potential link between AH¯ molecules and a defense response in A. mellifera larvae against infection, consistent with their resistance to P. larvae (LD50).

A Novel pH-sensitive Nanocomposite Based on Graphene Oxide for Improving Doxorubicin Release

BACKGROUND

Doxorubicin (DOX) as a chemotherapeutic drug has been widely used for treatment of cancer but because of adverse side effects of this drug, different drug delivery systems have been tested. One of them has been immobilization of DOX on the graphene oxide (GO) sheets through non-covalent interactions (GO-DOX) with high efficiency however the release was very low and slow due to strong forces between DOX and GO.

OBJECTIVE

The aim of this research was to increase the release of DOX and this goal was achieved through the covalent binding of DOX to the GO-poly(ethyleneimine) 2KDa conjugate.

METHODS

A novel nanocarrier for delivering DOX was fabricated using GO as a basic plane for conjugating and assembling other compounds. DOX was attached to GO-poly(ethyleneimine) 2KDa conjugate via a linker containing hydrazide bond. Drug loading and release was investigated at pH 7.5 and pH 5.5. Cytotoxicity was determined by MTT on MCF7 cells and compared with previous nanocarrier.

RESULTS

The fabrication of the nanocarrier and the covalent attachment of DOX to the nanocarrier were confirmed through FT-IR spectroscopy. The capacity of nanocarrier to load drug was as high as 383%. 96% of initial drug was loaded in the nanocarrier. The weight percentage of the drug in the nanocarrierdrug conjugate was 79%. Release of drug at pH 5.5 was two times more than release at pH 7.5 and this evidence supports conjugation of DOX to nanocarrier through hydrazide bond and pH-sensitivity of related bond. Because of the reliable results, ease of operation, safety and high reproducibility, MTT was chosen to evaluate the cytotoxicity of samples. Nanocarrier didn't show significant toxicity even at high concentrations. IC50 value for chemically-bound DOX to hydrazide-containing GO nanocomposite was 9.5 μg/ml whereas the IC50 value for GO-DOX was 39 μg/ml after 72 h. Loading of DOX via hydrazide bond was as low as 4% versus near 75% physical loading of drug while hydrazide bondcontaining nanocomposite was 4 to 6 fold more toxic than GO-DOX.

CONCLUSION

Based on the obtained data, the covalent attachment of DOX to the nanocarrier through hydrazide linkers was an interesting idea that increased drug release and toxicity despite much lower percentage of covalent attachment compared to non-covalent immobilization. As could be concluded from this study, nanocarriers based on hydrazide bond could be a good candidate for drug delivery.

CCL2 chemokine inhibition primes the tumor vasculature for improved nanomedicine delivery and efficacy

Blood vessel functionality is crucial for efficient tumor-targeted drug delivery. Heterogeneous distribution and perfusion of angiogenic blood vessels contribute to suboptimal accumulation of (nano-) therapeutics in tumors and metastases. To attenuate pathological angiogenesis, an L-RNA aptamer inhibiting the CC motif chemokine ligand 2 (CCL2) was administered to mice bearing orthotopic 4T1 triple-negative breast cancer tumors. The effect of CCL2 inhibition on tumor blood vessel functionality and tumor-targeted drug delivery was evaluated via multimodal and multiscale optical imaging, employing fluorophore-labeled polymeric (10 nm) and liposomal (100 nm) nanocarriers. Anti-CCL2 treatment induced a dose-dependent anti-angiogenic effect, reflected by a decreased relative blood volume, increased blood vessel maturity and functionality, and reduced macrophage infiltration, accompanied by a shift in the polarization of tumor-associated macrophages (TAM) towards a less M2-like and more M1-like phenotype. In line with this, CCL2 inhibitor treatment improved the delivery of polymers and liposomes to tumors, and enhanced the antitumor efficacy of free and liposomal doxorubicin. Together, these findings demonstrate that blocking the CCL2-CCR2 axis modulates TAM infiltration and polarization, resulting in vascular normalization and improved tumor-targeted drug delivery.

Singlet Oxygen and Superoxide Anion Radical Detection by EPR Spin Trapping in Thylakoid Preparations

Reactive oxygen species (ROS) are produced by energy transfer and electron transport in plant chloroplast thylakoids at non-toxic levels under normal growth conditions, but at threatening levels under adverse or fluctuating environmental conditions. Among chloroplast ROS, singlet oxygen and superoxide anion radical, respectively, produced by photosystem II (PSII) and PSI, are known to be the major ROS under several stress conditions. Both are very unlikely to diffuse out of chloroplasts, but they are instead capable of triggering ROS-mediated chloroplast operational retrograde signalling to activate defence gene expression in concert with hormones and other molecular compounds. Therefore, their detection, identification and localization in vivo or in biological preparations is a priority for a deeper understanding of their role in (concurrent) regulation of plant growth and defence responses. Here, we present two EPR spin traps, abbreviated as TEMPD-HCl and DEPMPO, to detect and identify ROS in complex systems, such as isolated thylakoids, together with some hints and cautions to perform reliable spin trapping experiments.

PDSFit: PDS data analysis in the presence of orientation selectivity, g-anisotropy, and exchange coupling

Pulsed dipolar electron paramagnetic resonance spectroscopy (PDS), encompassing techniques such as pulsed electron-electron double resonance (PELDOR or DEER) and relaxation-induced dipolar modulation enhancement (RIDME), is a valuable method in structural biology and materials science for obtaining nanometer-scale distance distributions between electron spin centers. An important aspect of PDS is the extraction of distance distributions from the measured time traces. Most software used for this PDS data analysis relies on simplifying assumptions, such as assuming isotropic g-factors of ~2 and neglecting orientation selectivity and exchange coupling. Here, the program PDSFit is introduced, which enables the analysis of PELDOR and RIDME time traces with or without orientation selectivity. It can be applied to spin systems consisting of up to two spin centers with anisotropic g-factors and to spin systems with exchange coupling. It employs a model-based fitting of the time traces using parametrized distance and angular distributions, and parametrized PDS background functions. The fitting procedure is followed by an error analysis for the optimized parameters of the distributions and backgrounds. Using five different experimental data sets published previously, the performance of PDSFit is tested and found to provide reliable solutions.

Is it now time to iron out the wrinkles? Health of Shar Pei dogs under primary veterinary care in the UK

BACKGROUND

The Shar Pei is a common dog breed with a distinctive appearance caused by hyaluronosis that has been linked with several health conditions. Anonymised primary-care veterinary clinical records were explored to extract data on the demography, common disorders and mortality of Shar Pei in the UK in 2013.

RESULTS

The study population of 455,557 dogs included 1913 (0.42%) Shar Pei. The mean adult bodyweight was 22.26 kg. The most prevalent fine-level precision disorders were entropion (prevalence 17.88%, 95% CI: 16.16-19.59), otitis externa (16.36%, 95% CI: 14.70-18.02), ear disorders (6.69%, 95% CI: 5.57-7.81), aggression (5.23%, 95% CI: 4.23-6.22), and pyoderma (4.29%, 95% CI: 3.38-5.19). The most prevalent disorder groups were ophthalmologic (prevalence = 22.27%, 95% CI: 20.40-24.13), dermatological (21.01%, 95% CI: 19.19-22.84), aural (18.66%, 95% CI: 16.92-20.41), traumatic injury (7.53%, 95% CI: 6.35-8.71) and behavioural (7.21%, 95% CI: 6.05-8.37). The median longevity of 190 Shar Pei that died during the study period was 7.28 years (IQR 5.04-10.05, range 0.04-15.04). Of 184 deaths with a recorded method of death, 157 (85.33%) deaths involved euthanasia and 27 (14.67%) deaths were unassisted. Among 136 (71.58%) deaths with a recorded biomedical cause of death, the most common causes of death at group level precision were neoplasia (15.44%, 95% CI: 9.37-21.51), renal disorders (13.24%, 95% CI: 7.54-18.93), and behavioural disorders (11.03%, 95% CI: 5.76-16.29).

CONCLUSIONS

Almost one fifth of Shar Pei receive veterinary care each year for entropion, a condition linked strongly with the extreme conformation of thickened and folded skin and bristly hair that characterises the Shar Pei breed. Several other common disorders are also linked to hyaluronosis. Current UK legislation can help support efforts to avoid breeding or acquiring animals with extreme conformations and to promote adequate veterinary care for already-owned animals with extreme conformations.

Aerobic Oxidation of 5-Hydroxymethylfurfural (HMF) in Aqueous Medium over Fe-Doped-Poly(heptazine imide) Photocatalysts: Unveiling the Bad Role of Hydroxyl Radical Generation on the Catalytic Performance

5-hydroxymethylfurfural (HMF) oxidation in aqueous media using visible photocatalysis is a green and sustainable route for the valorization of lignocellulosic biomass derivatives. Several semiconductors have already been applied for this purpose; however, the use of Poly(heptazine imides), which has high crystallinity and a special cation exchange property that allows the replacement of the cation held between the layers of C3N4 structure by transition metal ions (TM), remains scarce. In this study, PHI(Na) was synthesized using a melamine/NaCl method and used as precursor to prepare metal (Fe, Co, Ni, or Cu)-doped PHI catalysts. The catalysts were tested for selective oxidation of HMF to 2,5-diformylfuran (DFF) in water and O2 atmosphere under blue LED radiation. The catalytic results revealed that the 0.1 wt% PHI(Fe) catalyst is the most efficient photocatalyst while higher Fe loading (1 and 2 wt%) favors the formation of Fe3+ clusters, which are responsible for the drop in HMF oxidation. Moreover, the 0.1 wt% PHI(Fe) photocatalyst has strong oxidative power due to its efficiency in H2O2 production, thus boosting the generation of nonselective hydroxyl radicals (●OH) via different pathways that can destroy HMF. We found that using 50 mM, the highest DFF production rate (393 μmol·h-1·g-1) was obtained in an aqueous medium under visible light radiation.

Imaging in Type 1 Diabetes, Current Perspectives and Directions

Type 1 diabetes (T1D) is characterized by the autoimmune-mediated attack of insulin-producing beta cells in the pancreas, leading to reliance on exogenous insulin to control a patient's blood glucose levels. As progress is being made in understanding the pathophysiology of the disease and how to better develop therapies to treat it, there is an increasing need for monitoring technologies to quantify beta cell mass and function throughout T1D progression and beta cell replacement therapy. Molecular imaging techniques offer a possible solution through both radiologic and non-radiologic means including positron emission tomography, magnetic resonance imaging, electron paramagnetic resonance imaging, and spatial omics. This commentary piece outlines the role of molecular imaging in T1D research and highlights the need for further applications of such methodologies in T1D.

Cationic Proteins Rich in Lysine Residue Trigger Formation of Non-bilayer Lipid Phases in Model and Biological Membranes: Biophysical Methods of Study

Cationic membrane-active toxins are the most abundant group of proteins in the venom of snakes and insects. Cationic proteins such as cobra venom cytotoxin and bee venom melittin are known for their pharmacological reactions including anticancer and antimicrobial effects which arise from the toxin-induced alteration in the dynamics and structure of plasma membranes and membranes of organelles. It has been established that these cationic toxins trigger the formation of non-bilayer lipid phase transitions in artificial and native mitochondrial membranes. Remarkably, the toxin-induced formation of non-bilayer lipid phase increases at certain conditions mitochondrial ATP synthase activity. This observation opens an intriguing avenue for using cationic toxins in the development of novel drugs for the treatment of cellular energy deficiency caused by aging and diseases. This observation also warrants a thorough investigation of the molecular mechanism(s) of lipid phase polymorphisms triggered by cationic proteins. This article presents a review on the application of powerful biophysical methods such as resonance spectroscopy (31P-, 1H-, 2H-nuclear magnetic resonance, and electron paramagnetic resonance), luminescence, and differential scanning microcalorimetry in studies of non-bilayer lipid phase transitions triggered by cationic proteins in artificial and biological membranes. A phenomenon of the triggered by cationic proteins the non-bilayer lipid phase transitions occurring within 10-2-10-11 s is discussed in the context of potential pharmacological applications of cationic proteins. Next to the ATP dimer is an inverted micelle made of cardiolipin that serves as a vehicle for the transport of H+ ions from the intra-crista space to the matrix. It is proposed that such inverted micelles are triggered by the high density of H+ ions and the cationic proteins rich in lysine residue which compete with the conserved lysine residues of the ATP synthase rotor for binding to cardiolipin in the inner mitochondrial membrane and perturb the bilayer lipid packing of cristae. Phospholipids with a blue polar head represent cardiolipin and those with a red polar head represent other phospholipids found in the crista membrane.

Identification of defect centers responsible for thermoluminescence emission in sol-gel synthesized calcium silicate phosphor

The thermoluminescence (TL) of calcium silicate phosphor (CSO) prepared by the sol-gel method and sintered at 1200 °C were investigated. From Tm-Tstop curve, TL emission spectrum and computer deconvolution using electron traps with discrete and continuous distributions, the glow curves were found to be composed of four TL peaks (117, 190, 250 and 275 °C) with a single emission band centered at 370 nm. Electron paramagnetic resonance (EPR) investigation has been carried out to identify the defect centers formed in the CSO phosphor by γ-irradiation and find the centers related to the TL process in the phosphor. At room temperature, three defect centers were observed. The first center, characterized by the principal g-values of 2.014, 2.011, and 2.0080 was assigned to an O- ion. The second center with g-values 2.015, 2.013, and 2.010 is also attributed to an O- ion and is associated with the TL peak at 280 °C. The third center, with an isotropic g-value of 2.0011 was identified as the F+ center (singly ionized oxygen vacancy) and relates to the TL peak at 280 °C.

Photocatalytic Dehalogenative Deuteration of Halides over a Robust Metal-Organic Framework

Deuterium labelling of organic compounds is an important process in chemistry. We report the first example of photocatalytic dehalogenative deuteration of both arylhalides and alkylhalides (40 substrates) over a metal-organic framework, MFM-300(Cr), using CD3 CN as the deuterium source at room temperature. MFM-300(Cr) catalyses high deuterium incorporation and shows excellent tolerance to various functional groups. Synchrotron X-ray powder diffraction reveals the activation of halogenated substrates via confined binding within MFM-300(Cr). In situ electron paramagnetic resonance spectroscopy confirms the formation of carbon-based radicals as intermediates and reveals the reaction pathway. This protocol removes the use of precious-metal catalysts from state-of-the-art processes based upon direct hydrogen isotope exchange and shows high photocatalytic stability, thus enabling multiple catalytic cycles.

Pyruvate formate-lyase activating enzyme: The catalytically active 5'-deoxyadenosyl radical caught in the act of H-atom abstraction

Enzymes of the radical S-adenosyl-l-methionine (radical SAM, RS) superfamily, the largest in nature, catalyze remarkably diverse reactions initiated by H-atom abstraction. Glycyl radical enzyme activating enzymes (GRE-AEs) are a growing class of RS enzymes that generate the catalytically essential glycyl radical of GREs, which in turn catalyze essential reactions in anaerobic metabolism. Here, we probe the reaction of the GRE-AE pyruvate formate-lyase activating enzyme (PFL-AE) with the peptide substrate RVSG734YAV, which mimics the site of glycyl radical formation on the native substrate, pyruvate formate-lyase. Time-resolved freeze-quench electron paramagnetic resonance spectroscopy shows that at short mixing times reduced PFL-AE + SAM reacts with RVSG734YAV to form the central organometallic intermediate, Ω, in which the adenosyl 5'C is covalently bound to the unique iron of the [4Fe-4S] cluster. Freeze-trapping the reaction at longer times reveals the formation of the peptide G734• glycyl radical product. Of central importance, freeze-quenching at intermediate times reveals that the conversion of Ω to peptide glycyl radical is not concerted. Instead, homolysis of the Ω Fe-C5' bond generates the nominally "free" 5'-dAdo• radical, which is captured here by freeze-trapping. During cryoannealing at 77 K, the 5'-dAdo• directly abstracts an H-atom from the peptide to generate the G734• peptide radical trapped in the PFL-AE active site. These observations reveal the 5'-dAdo• radical to be a well-defined intermediate, caught in the act of substrate H-atom abstraction, providing new insights into the mechanistic steps of radical initiation by RS enzymes.

Magnetic Resonance-Based Analytical Tools to Study Polyvinylpyrrolidone-Hydroxyapatite Composites

The synthesis of biocompatible and bioresorbable composite materials, such as a "polymer matrix-mineral constituent," stimulating the natural growth of living tissues and the restoration of damaged parts of the body, is one of the challenging problems in regenerative medicine and materials science. Composite films of bioresorbable polymer of polyvinylpyrrolidone (PVP) and hydroxyapatite (HA) were obtained. HA was synthesized in situ in the polymer solution. We applied electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR) approaches to study the composite films' properties. The application of EPR in two frequency ranges allowed us to derive spectroscopic parameters of the nitrogen-based light and radiation-induced paramagnetic centers in HA, PVP and PVP-HA with high accuracy. It was shown that PVP did not significantly affect the EPR spectral and relaxation parameters of the radiation-induced paramagnetic centers in HA, while light-induced centers were detected only in PVP. Magic angle spinning (MAS) 1H NMR showed the presence of two signals at 4.7 ppm and -2.15 ppm, attributed to "free" water and hydroxyl groups, while the single line was attributed to 31P. NMR relaxation measurements for 1H and 31P showed that the relaxation decays were multicomponent processes that can be described by three components of the transverse relaxation times. The obtained results demonstrated that the applied magnetic resonance methods can be used for the quality control of PVP-HA composites and, potentially, for the development of analytical tools to follow the processes of sample treatment, resorption, and degradation.

Hydroxytyrosol Counteracts Triple Negative Breast Cancer Cell Dissemination via Its Copper Complexing Properties

Polyphenols have gained increasing attention for their therapeutic potential, particularly in conditions like cancer, due to their established antioxidant and anti-inflammatory properties. Recent research highlights their ability to bind to transition metals, such as copper. This is particularly noteworthy given the key role of copper both in the initiation and progression of cancer. Copper can modulate the activity of kinases required for the epithelial-mesenchymal transition (EMT), a process fundamental to tumor cell dissemination. We have previously demonstrated the copper-binding capacity of oleuropein, a secoiridoid found in Olea europaea. In the present study, we investigated the effect of hydroxytyrosol, the primary oleuropein metabolite, on the metastatic potential of three triple-negative breast cancer cell lines (MDA-MB-231, MDA-MB-468, and SUM159). We found that hydroxytyrosol modulated the intracellular copper levels, influencing both the epithelial and mesenchymal markers, by downregulating copper-dependent AKT phosphorylation, a member of the EMT signaling cascade, through Western blot, RT-qPCR, and immunofluorescence. Indeed, by optical spectra, EPR, and in silico approaches, we found that hydroxytyrosol formed a complex with copper, acting as a chelating agent, thus regulating its homeostasis and affecting the copper-dependent signaling cascades. While our results bring to light the copper-chelating properties of hydroxytyrosol capable of countering tumor progression, they also provide further confirmation of the key role of copper in promoting the aggressiveness of triple-negative breast cancer cells.

SOX71, A Biocompatible Succinyl Derivative of the Triarylmethyl Radical OX071 for In Vivo Quantitative Oxygen Mapping Using Electron Paramagnetic Resonance

PURPOSE

This study aimed to develop a biocompatible oximetric electron paramagnetic resonance (EPR) spin probe with reduced self-relaxation, and sensitivity to oxygen for a higher signal-to-noise ratio and longer relaxation times at high oxygen concentration, compared to the reference spin probe OX071.

PROCEDURES

SOX71 was synthesized by succinylation of the twelve alcohol groups of OX071 spin probe and characterized by EPR at X-Band (9.5 GHz) and at low field (720 MHz). The biocompatibility of SOX71 was tested in vitro and in vivo in mice. A pharmacokinetic study was performed to determine the best time frame for EPR imaging. Finally, a proof-of-concept EPR oxygen imaging was performed on a mouse model of a fibrosarcoma tumor.

RESULTS

SOX71 was synthesized in one step from OX071. SOX71 exhibits a narrow line EPR spectrum with a peak-to-peak linewidth of 66 mG, similar to OX071. SOX71 does not bind to albumin nor show cell toxicity for the concentrations tested up to 5 mM. No toxicity was observed after systemic delivery via intraperitoneal injection in mice at twice the dose required for EPR imaging. After the injection, the probe is readily absorbed into the bloodstream, with a peak blood concentration half an hour, post-injection. Then, the probe is quickly cleared by the kidney with a half-life of ~ 45 min. SOX71 shows long relaxation times under anoxic condition (T1e = 9.5 µs and T2e = 5.1 µs; [SOX71] = 1 mM in PBS at 37 °C, pO2 = 0 mmHg, 720 MHz). Both the relaxation rates R1e and R2e show a decreased sensitivity to pO2, leading to twice longer relaxation times under room air conditions (pO2 = 159 mmHg) compared to OX071. This is ideal for oxygen imaging in samples with a wide range of pO2. Both the relaxation rates R1e and R2e show a decreased sensitivity to self-relaxation compared to OX071, with a negligible effect of the probe concentration on R1e. SOX71 was successfully applied to image oxygen in a tumor.

CONCLUSION

SOX71, a succinylated derivative of OX071 was synthesized, characterized, and applied for in vivo EPR tumor oxygen imaging. SOX71 is highly biocompatible, and shows decreased sensitivity to oxygen and self-relaxation. This first report suggests that SOX71 is superior to OX071 for absolute oxygen mapping under a broad range of pO2 values.

New Sustainable Solvent Extraction Pathways for Rare Earth Metals via Oximes Molecules

A study on the synergistic extraction of Eu(III) ions with a series of chelating ligands and determination of the process parameters is presented by employing ionic liquids and typical organic diluents. The investigations of the liquid-liquid extraction, commonly applied in the separation science of 4f and 5f-ions acidic chelating compounds, 4-benzoyl-3-methyl-1-phenyl-2-pyrazolin-5-one (HP), 4-benzoyl-3-phenyl-5-isoxazolone (HPBI), and 2-thenoyltrifluoroacetone (HTTA) alone and in combination with two synergistic agents, meso-hexamethylpropyleneamine oxime (S2: HM-PAO) and its bis-imine precursor (S1: pre-HM-PAO), are presented. The interaction between the two extractants (acidic/neutral) in deuterochloroform was studied using 1H, 13C, and 1H-1H NOESY experiments. Several conclusions are given highlighting the role of the ionic diluent in complexation processes and selectivity with an employment of the two synergistic agents for various metal s-, p-, d-, and f-cations in the Periodic table, with almost 25 metal ions. The objective was to optimize a system for 4f-ions solvent extraction based on the new oxime molecules with β-diketone/isoxazolone/pyrazolone partnership. As detailed above, slight enhancements of extraction efficiencies were obtained either by using basic synergistic agents such as HM-PAO and/or using pre-HM-PAO. A competitive solvent extraction test of nearly 18 f-ions by various ligands (HTTA, S1, S2, and HPBI) and the two mixtures HTTA-S1 and HTTA-S2 diluted in ILs or organic diluents was also conducted in order to evaluate the switchable diluent impact. Additionally, electron paramagnetic resonance (EPR) spectroscopy was used to study the established chemical species with Cu2+ cations in the obtained organic extracts involving the two synergistic molecules.

Phosphorus doped cyanobacterial biochar catalyzes efficient persulfate oxidation of the antibiotic norfloxacin

In this study, cyanobacterial biochars (CBs) enriched/doped with non-metallic elements were prepared by pyrolysis of biomass amended with different N, S, and P containing compounds. Their catalytic reactivity was tested for persulfate oxidation of the antibiotic norfloxacin (NOR). N and S doping failed to improve CB catalytic reactivity, while P doping increased reactivity 5 times compared with un-doped biochar. Biochars produced with organic phosphorus dopants showed the highest reactivity. Post-acid-washing improved catalytic reactivity. In particular, 950 ℃ acid-washed triphenyl-phosphate doped CB showed the largest degradation rate and reached 79% NOR mineralization in 2 h. Main attributes for P-doped CBs high reactivity were large specific surface areas (up to 655 m2/g), high adsorption, high C-P-O content, graphitic P and non-radical degradation pathway (electron transfer). This study demonstrates a new way to reuse waste biomass by producing efficient P-doped metal-free biochars and presents a basic framework for designing carbon-based catalysts for organic pollutant degradation.

Oxidation 1-methyl naphthalene based on the synergy of environmentally persistent free radicals (EPFRs) and PAHs in particulate matter (PM) surface

Studies of the environmental fate through the interactions of particle-associated polycyclic aromatic hydrocarbons (PAHs) with environmentally persistent free radicals (EPFRs) are presented. The formation of PAHs and EPFRs typically occurs side by side during combustion-processes. The laboratory simulation studies of the model PAH molecule 1-Methylnaphthalene (1-MN) interaction with model EPFRs indicate a transformational synergy between these two pollutants due to mutual and matrix interactions. EPFRs, thorough its redox cycle result in the oxidation of PAHs into oxy-/hydroxy-PAHs. EPFRs have been shown before to produce OH radical during its redox cycle in aqueous media and this study has shown that produced OH radical can transform other PM constituents resulting in alteration of PM chemistry. In model PM, EPFRs driven oxidation process of 1-MN produced 1,4-naphthoquinone, 1-naphthaldehyde, 4-hydroxy-4-methylnaphthalen-1-one, and various isomers of (hydroxymethyl) naphthalene. Differences were observed in oxidation product yields, depending on whether EPFRs and PAHs were cohabiting the same PM or present on separate PM. This effect is attributed to the OH radical concentration gradient as a factor in the oxidation process, further strengthening the hypothesis of EPFRs' role in the PAH oxidation process. This finding is revealing new environmental role of EPFRs in a natural degradation process of PAHs. Additionally, it points to implications of such PM surface chemistry in the changing mobility of PAHs into an aqueous medium, thus increasing their bioavailability.

Q-band EPR cryoprobe

Following the success of cryogenic EPR signal preamplification at X-band, we present a Q-band EPR cryoprobe compatible with a standard EPR resonator. The probehead is equipped with a cryogenic ultra low-noise microwave amplifier and its protection circuit that are placed close to the sample in the same cryostat. Our cryoprobe maintains the same sample access and tuning which is typical in Q-band EPR, as well as supports high-power pulsed experiments on typical samples. The performance of our setup is benchmarked against that of existing commercial and home-built Q-band spectrometers, using CW EPR and pulsed EPR/ENDOR experiments to reveal a significant sensitivity improvement which reduces the measurement time by a factor of about 40× at 6 K temperature at reduced power levels.

Macroscopic sample shape effect on pulse electron double resonance (PELDOR) signal

Pulse electron double resonance (PELDOR), also called double electron-electron resonance (DEER), is a technique capable of measuring the strength of electron spin dipolar interactions, revealing spin-spin distance distributions in ordered and disordered solid materials. Previous work has shown that PELDOR signals acquire an out-of-phase component under conditions of high electron spin polarization, such as at low temperatures and high fields. In this paper, we show theoretically and experimentally that the size and sign of this effect depends on the macroscopic shape of the sample and its orientation in the external magnetic field. This effect is caused by dipolar interactions between distant spins and provides new insights into the fundamental physics of PELDOR.