Magnetic Field Effect in Bimolecular Rate Constant of Radical Recombination.

The influence of magnetic fields on chemical reactions, including biological ones, has been and still is a topical subject in the field of scientific research. Experimentally discovered and theoretically substantiated magnetic and spin effects in chemical radical reactions form the basis of research in the field of spin chemistry. In the present work, the effect of a magnetic field on the rate constant of the bimolecular spin-selective recombination of radicals in the bulk of a solution is considered theoretically for the first time, taking into account the hyperfine interaction of radical spins with their magnetic nuclei.

Comparative Analysis of Molecular Functions and Biological Role of Proteins from Cell-Free DNA-Protein Complexes Circulating in Plasma of Healthy Females and Breast Cancer Patients.

Cell-free DNA (cfDNA) circulates in the bloodstream packed in membrane-coated structures (such as apoptotic bodies) or bound to proteins. To identify proteins involved in the formation of deoxyribonucleoprotein complexes circulating in the blood, native complexes were isolated using affinity chromatography with immobilized polyclonal anti-histone antibodies from plasma of healthy females (HFs) and breast cancer patients (BCPs). It was found that the nucleoprotein complexes (NPCs) from HF plasma samples contained shorter DNA fragments (~180 bp) than BCP NPCs.

Sensitivity optimization in pulse EPR experiments with photo-labels by multiple-echo-integrated dynamical decoupling.

Photo-excited triplet states represent a new class of spin labels in pulse electron paramagnetic resonance (EPR), attracting increasing attention because of their unique spectroscopic properties. Despite certain advantages, the use of photo-labels has also some challenges, low repetition rates due to technical laser-related limitations and intrinsic properties of the labels. The application of additional pulse trains for multiple refocusing of the electron spin echo and integration of all observed echoes can significantly enhance sensitivity at a given repetition rate.

A new view on the mechanism of UV photodegradation of the tricyclic antidepressant carbamazepine in aqueous solutions.

Mechanism of direct UV photolysis of the tricyclic antidepressant carbamazepine (CBZ) at neutral pH was revealed by a combination of nanosecond laser flash photolysis, steady-state photolysis combined with high resolution LC-MS and DFT quantum-chemical calculations. The detection of short-lived intermediates and the detailed identification of final products were performed for the first time. The quantum yield of CBZ photodegradation (282 nm) is about 0.

The structural role and coordination environment of cobalt in 45PO-CaO-NaO phosphate glasses: thermal properties and Raman, UV-vis-NIR, and EPR spectroscopy.

Cobalt-containing materials are of interest for a wide range of applications, from biomaterials to solid-state lasers in optics. For instance, Co is known to trigger the formation of new blood vessels, angiogenesis. Here, the use of phosphate glasses as a vehicle for local release of Co ions is an attractive strategy to overcome the vascularisation limitation in tissue engineering.

Reduction of transient carnosine radicals depends on β-alanyl amino group charge.

Reduction of transient carnosine (β-alanyl-L-histidine) radicals by L-tryptophan, -acetyl tryptophan, and the Trp-Gly peptide in neutral and basic aqueous solutions was studied using the technique of time-resolved chemically induced dynamic nuclear polarization (TR CIDNP). Carnosine radicals were generated in the photoinduced reaction with triplet excited 3,3',4,4'-tetracarboxy benzophenone. In this reaction, carnosine radicals with their radical center at the histidine residue are formed.

Corrigendum to "CLIPPERS: Multiparametric and quantitative MRI features" [Radiology Case Reports 18 (2023) 368-376].

[This corrects the article DOI: 10.1016/j.radcr.

Hyperpolarizing DNA Nucleobases via NMR Signal Amplification by Reversible Exchange.

The present work investigates the potential for enhancing the NMR signals of DNA nucleobases by parahydrogen-based hyperpolarization. Signal amplification by reversible exchange (SABRE) and SABRE in Shield Enables Alignment Transfer to Heteronuclei (SABRE-SHEATH) of selected DNA nucleobases is demonstrated with the enhancement () of H, N, and/or C spins in 3-methyladenine, cytosine, and 6-O-guanine. Solutions of the standard SABRE homogenous catalyst Ir(1,5-cyclooctadeine)(1,3-bis(2,4,6-trimethylphenyl)imidazolium)Cl ("IrIMes") and a given nucleobase in deuterated ethanol/water solutions yielded low H values (≤10), likely reflecting weak catalyst binding.

Heavily Gd-Doped Non-Toxic Cerium Oxide Nanoparticles for MRI Labelling of Stem Cells.

Recently, human mesenchymal stem cells (hMSc) have attracted a great deal of attention as potential therapeutic agents in the treatment of socially significant diseases. Despite substantial advances in stem-cell therapy, the biological mechanisms of hMSc action after transplantation remain unclear. The use of magnetic resonance imaging (MRI) as a non-invasive method for tracking stem cells in the body is very important for analysing their distribution in tissues and organs, as well as for ensuring control of their lifetime after injection.

Spin Hyperpolarization in Modern Magnetic Resonance.

Magnetic resonance techniques are successfully utilized in a broad range of scientific disciplines and in various practical applications, with medical magnetic resonance imaging being the most widely known example. Currently, both fundamental and applied magnetic resonance are enjoying a major boost owing to the rapidly developing field of spin hyperpolarization. Hyperpolarization techniques are able to enhance signal intensities in magnetic resonance by several orders of magnitude, and thus to largely overcome its major disadvantage of relatively low sensitivity.

Fluorescently labeled human apurinic/apyrimidinic endonuclease APE1 reveals effects of DNA polymerase β on the APE1-DNA interaction.

The base excision repair (BER) pathway involves sequential action of DNA glycosylases and apurinic/apyrimidinic (AP) endonucleases to incise damaged DNA and prepare DNA termini for incorporation of a correct nucleotide by DNA polymerases. It has been suggested that the enzymatic steps in BER include recognition of a product-enzyme complex by the next enzyme in the pathway, resulting in the "passing-the-baton" model of transfer of DNA intermediates between enzymes. To verify this model, in this work, we aimed to create a suitable experimental system.

The Effect of Dietary Phospholipids on the Ultrastructure and Function of Intestinal Epithelial Cells.

Dietary composition substantially determines human health and affects complex diseases, including obesity, inflammation and cancer. Thus, food supplements have been widely used to accommodate dietary composition to the needs of individuals. Among the promising supplements are dietary phospholipids (PLs) that are commonly found as natural food ingredients and as emulsifier additives.

Blatter Radical-Decorated Silica as a Prospective Adsorbent for Selective NO Capture from Air.

Nitrogen oxides are adverse poisonous gases present in the atmosphere and having detrimental effects on the human health and environment. In this work, we propose a new type of mesoporous materials capable of capturing nitrogen monoxide (NO) from air. The designed material combines the robust Santa Barbara Amorphous-15 silica scaffold and ultrastable Blatter-type radicals acting as NO traps.

Parahydrogen-Induced Hyperpolarization of Unsaturated Phosphoric Acid Derivatives.

Parahydrogen-induced nuclear polarization offers a significant increase in the sensitivity of NMR spectroscopy to create new probes for medical diagnostics by magnetic resonance imaging. As precursors of the biocompatible hyperpolarized probes, unsaturated derivatives of phosphoric acid, propargyl and allyl phosphates, are proposed. The polarization transfer to H and P nuclei of the products of their hydrogenation by parahydrogen under the ALTADENA and PASADENA conditions, and by the PH-ECHO-INEPT+ pulse sequence of NMR spectroscopy, resulted in a very high signal amplification, which is among the largest for parahydrogen-induced nuclear polarization transfer to the P nucleus.

Change in the Electronic Structure of the Cobalt(II) Ion in a One-Dimensional Polymer with Flexible Linkers Induced by a Structural Phase Transition.

A new 1D-coordination polymer [Co(Piv)(NH(CH)NH)] (, Piv is MeCCO anion) was obtained, the mononuclear fragments {Co(OCR)} within which are linked by μ-bridged molecules of hexamethylenediamine (NH(CH)NH). For this compound, two different monoclinic 2/ (α-) and 2/ (β-) phases were found at room temperature by single-crystal X-ray diffraction analysis, with a similar structure of chains and their packages in unit cells. The low-temperature phase (γ-) of crystal at 150 K corresponds to the triclinic space group -1.

Influence of Ecological Factors on the Metabolomic Composition of Fish Lenses.

Multiple stressors related to changes in environmental conditions (such as water temperature, salinity, and natural and anthropogenic pollution) may cause biological responses of aquatic organisms that lead to significant variations in the biochemical reactions in their tissues and thereby change the concentrations of metabolites. We used a quantitative NMR-based metabolomic analysis of the fish lens for the evaluation of the influence of environmental factors on metabolic processes in aquatic animals. For this purpose, three species of freshwater fish-Perca fluviatilis, Rutilus rutilus lacustris, and Gymnocephalus cernua-were caught at approximately the same time at three locations in Siberia (Russia) that differed in levels of dissolved oxygen (LDO) and water purity, and the concentrations of 57 major metabolites in the fish lenses were determined.

Synthesis, crystal polymorphism and spin crossover behavior of adamantylboron-capped cobalt(II) hexachloroclathrochelate and its transformation into the CoCoCo-bis-macrobicyclic derivative.

Fast crystallization of the monoclathrochelate cobalt(II) intracomplex [Co(ClGm)(BAd)] (where ClGm is a dichloroglyoxime dianion and BAd is an adamantylboron capping group, 1), initially obtained by the direct template condensation of the corresponding chelating α-dioximate and cross-linking ligand synthons on the Co ion as a matrix, from benzene or dichloromethane afforded its structural triclinic and hexagonal polymorphs. Its prolonged recrystallization from dichloromethane under air atmosphere and sunlight irradiation unexpectedly gave the crystals of the CoCoCo-trinuclear dodecachloro-bis-clathrochelate intracomplex [[Co(ClGm)(BAd)]Co] (2), the molecule of which consists of two macrobicyclic frameworks with encapsulated low-spin (LS) Co ions, which are cross-linked by a μ-bridging Co ion as a bifunctional Lewis-acidic center. The most plausible pathway of such a 1 → 2 transformation is based on the photoinitiated radical oxidation of dichloromethane with air oxygen giving the reactive species.

A long-lived charge-separated state of spiro compact electron donor-acceptor dyads based on rhodamine and naphthalenediimide chromophores.

Spiro rhodamine (Rho)-naphthalenediimide (NDI) electron donor-acceptor orthogonal dyads were prepared to generate a long-lived charge separation (CS) state based on the electron spin control approach, to form the CS state, not the CS state, to prolong the CS state lifetime by the electron spin forbidden feature of the charge recombination process of CS → S. The electron donor Rho (lactam form) is attached three σ bonds, including two C-C and one N-N bonds (Rho-NDI), or an intervening phenylene, to the electron acceptor NDI (Rho-Ph-NDI and Rho-PhMe-NDI). Transient absorption (TA) spectra show that fast intersystem crossing (ISC) (<120 fs) occurred to generate an upper triplet state localized on the NDI moiety (NDI*), and then to form the CS state.

Charge Transfer Chromophores Derived from 3d-Row Transition Metal Complexes.

A series of new charge transfer (CT) chromophores of "α-diimine-M-catecholate" type (where M is 3d-row transition metals-Cu, Ni, Co) were derived from 4,4'-di--butyl-2,2'-bipyridyl and 3,6-di--butyl--benzoquinone () in accordance with three modified synthetic approaches, which provide high yields of products. A square-planar molecular structure is inherent for monomeric () and () chromophores, while dimeric complex () units two substantially distorted heteroleptic D-M-A (where D, M, A are donor, metal and acceptor, respectively) parts through a donation of oxygen atoms from catecholate dianions. Chromophores - undergo an effective photoinduced intramolecular charge transfer (λ = 500-715 nm, extinction coefficient up to 10 M·cm) with a concomitant generation of a less polar excited species, the energy of which is a finely sensitive towards solvent polarity, ensuring a pronounced negative solvatochromic effect.

Geometrization for Energy Levels of Isotropic Hyperfine Hamiltonian Block and Related Central Spin Problems for an Arbitrarily Complex Set of Spin-1/2 Nuclei.

Description of interacting spin systems relies on understanding the spectral properties of the corresponding spin Hamiltonians. However, the eigenvalue problems arising here lead to algebraic problems too complex to be analytically tractable. This is already the case for the simplest nontrivial (Kmax−1) block for an isotropic hyperfine Hamiltonian for a radical with spin-12 nuclei, where n nuclei produce an n-th order algebraic equation with n independent parameters.

Structural Anomaly in Glasses: Molecular Dynamics Study of Organic Radical in Dibutylphthalate at Different Temperatures.

Understanding the heterogeneous nano/microscopic structures of various organic glasses is fundamental and necessary for many applications. Recently, unusual structural phenomena have been observed experimentally in various organic glasses near their glass transition temperatures (Tg), including dibutyl phthalate (DBP). In particular, the librational motion of radical probe in the glass is progressively suppressed upon temperature increase.

Changes in Brain Activity in Healthy Women during Self-Regulation of Slow EEG Activity in the Prefrontal Cortex.

Frontal alpha asymmetry neurofeedback is used in affective disorders; however, little is known about the effects of this protocol on the composition of brain networks. In the current study, 13 healthy women underwent a course of self-regulation of the asymmetry of the EEG alpha or theta (control condition) band power. Before and after the course, resting state fMRI recordings were made.

Synthesis and Single-Electron Oxidation of Bulky Bis(m-terphenyl)chalcogenides: The Quest for Kinetically Stabilized Radical Cations.

Sterically encumbered bis(m-terphenyl)chalcogenides, (2,6-Mes C H ) E (E=S, Se, Te) were obtained by the reaction of the chalcogen tetrafluorides, EF , with three equivalents of m-terphenyl lithium, 2,6-Mes C H Li. The single-electron oxidation of (2,6-Mes C H ) Te using XeF /K[B(C F ) ] afforded the radical cation [(2,6-Mes C H ) Te][B(C F ) ] that was isolated and fully characterized. The electrochemical oxidation of the lighter homologs (2,6-Mes C H ) E (E=S, Se) was irreversible and impaired by rapid decomposition.

CLIPPERS: Multiparametric and quantitative MRI features.

Chronic lymphocytic inflammation with pontine perivascular enhancement responsive to steroids (CLIPPERS) is a rare chronic central-nervous-system inflammatory disorder that became known only recently, and the pathogenesis of CLIPPERS remains poorly understood. This report presents clinical and radiological features of a rare case: a young female patient who rapidly died of suspected CLIPPERS. Helpful multiparametric MRI diagnostic criteria are proposed that can help discriminate CLIPPERS from non-CLIPPERS pathologies.

Ferromagnetic Layers in a Topological Insulator (Bi,Sb)Te Crystal Doped with Mn.

Magnetic topological insulators (MTIs) have recently become a subject of poignant interest; among them, Z topological insulators with magnetic moment ordering caused by embedded magnetic atoms attract special attention. In such systems, the case of magnetic anisotropy perpendicular to the surface that holds a topologically nontrivial surface state is the most intriguing one. Such materials demonstrate the quantum anomalous Hall effect, which manifests itself as chiral edge conduction channels that can be manipulated by switching the polarization of magnetic domains.