Out-of-phase ELDOR spectroscopy: A precise tool for investigating structure and dynamics of charge-transfer states in organic photovoltaic blends.

We developed a technique allowing the direct observation of photoinduced charge-transfer states (CTSs)-the weakly coupled electron-hole pairs preceding the completely separated charges in organic photovoltaic (OPV) blends. Quadrature detection of the electron spin echo (ESE) signal enables the observation of an out-of-phase ESE signal of CTS. The out-of-phase Electron-Electron Double Resonance (ELDOR) allows measuring electron-hole distance distributions within CTS and its temporal evolution in the microsecond range.

Insights into Folding and Molecular Environment of Lyophilized Proteins Using Pulsed Electron Paramagnetic Resonance Spectroscopy.

There is still an insufficient understanding of how the characteristics of protein drugs are maintained in the solid state of lyophilizates, including aspects such as protein distances, local environment, and structural preservation. To this end, we evaluated protein folding and the molecules' nearest environment by electron paramagnetic resonance (EPR) spectroscopy. Double electron-electron resonance (DEER) probe distances of up to approximately 200 Å and is suitable to investigate protein folding, local concentration, and aggregation, whereas electron spin echo envelope modulation (ESEEM) allows the study of the near environment within approximately 10 Å of the spin label.

Effective radius of a contact diffusion-controlled reaction between small solutes and a polymer chain.

The aim of this study was to develop a formula for estimating the effective radius of a diffusion-controlled irreversible contact reaction between diffusing solutes and a nonlinear immobile polymer molecule. Analytical expressions for the reaction radius were obtained that took into account averaging over conformations for chains with arbitrary segment-to-segment angles and distributions of dihedral angles. A comparison of the analytical results with the results of computer stochastic modeling of the reaction showed good agreement over a wide range of parameters.

Slow magnetic relaxation and strong magnetic coupling in the nitroxyl radical complexes of lanthanide(iii) with diamagnetic ground state (Ln = Lu, Eu).

Radical lanthanide complexes are appealing platforms to investigate the possibility to engineer relevant magnetic couplings between the two magnetic centers by exploiting the strongly donating magnetic orbitals of the radical. In this paper, we report a spectroscopic and magnetic study on [LnRad(NO)], where Ln = Eu or Lu and Rad is the tridentate tripodal nitroxyl radical 4,4-dimethyl-2,2-bis(pyridin-2-yl)-1,3-oxazolidine-3-oxyl. A thorough magnetic investigation by Electron Paramagnetic Resonance (EPR) spectroscopy and magnetometry, fully supported by calculations, allowed us to unravel an unprecedentedly large antiferromagnetic coupling between the Eu and the radical ( = +19.

Adrenochrome formation during photochemical decomposition of "caged" epinephrine derivatives.

Control of biological activity with light is a fascinating idea. "Caged" compounds, molecules modified with photolabile protecting group, are one of the instruments for this purpose. Adrenergic receptors are essential regulators of neuronal, endocrine, cardiovascular, vegetative, and metabolic functions.

The influence of inactivated entomopathogenic bacterium on the immune responses of the Colorado potato beetle.

Background: Invasion of microorganisms into the gut of insects triggers a cascade of immune reactions accompanied by increased synthesis of effectors (such as antimicrobial peptides, cytokines, and amino acids), leading to changes in the physiological state of the host. We hypothesized that even an inactivated bacterium can induce an immune response in an insect. The aim of this study was to compare the roles of reactive oxygen species (ROS) formation and of the response of detoxification and antioxidant systems in a Colorado potato beetle (CPB) larval model in the first hours after invasion by either an inactivated or live bacterium.

Mechanism of UV photodegradation of fluoroquinolone antibiotic ciprofloxacin in aqueous solutions.

Mechanism of direct UV photolysis of the zwitterionic and anionic forms of the quinolone antibiotic ciprofloxacin (CIP) was revealed by combination of nanosecond laser flash photolysis, steady-state photolysis coupled with high resolution LC-MS and DFT quantum-chemical calculations. For both forms, the main intermediate is a dissociative triplet state, which loses a fluorine ion to form a triplet carbocation; subsequent solvent attack of the latter leads to the formation of products of hydroxylation both the aromatic ring and the piperazyl substituent. Correspondingly, the quantum yield of photolysis of both CIP forms does not depend on the excitation wavelength, but depends on the concentration of dissolved oxygen.

Temperature behavior of the velocity autocorrelation function in large MD models of water.

Velocity autocorrelation functions (VACFs) were calculated using the molecular dynamics method in the TIP4P/2005 and SPC/E water models of 157 464 molecules at temperatures ranging from 250 to 370 K. The large size of the models and the high accuracy of the calculations allow us to reliably compute the long-time tails of the VACFs, showing that they systematically change shape from hydrodynamic (argon-like) at high temperatures to that typical of supercooled liquids at low temperatures. These tails in the range of 2-10 ps can be well fitted by a combination of two power functions: At-3/2 - Bt-β (A, B > 0, β ≈ 2).

Cytotoxic and ROS generation activity of anthraquinones chelate complexes with metal ions.

Anthraquinones (AQs) are very effective chemotherapeutic agent, however their fundamental shortcoming is high cardiotoxicity caused by reactive oxygen species (ROS). Therefore, development of improved antitumor drugs with enhanced efficacy but reduced side effects remains a high priority. In the present study we evaluated the cytotoxicity and ROS generation activity of chelate complex of redox-active anthraquinone 2-phenyl-4-(butylamino)naphtho[2,3-h]quinoline-7,12-dione (Q1) with iron and copper ions.

Temperature Dependence of the Sensitivity of PVDF Pyroelectric Sensors to THz Radiation: Towards Cryogenic Applications.

The application of terahertz (THz) science in industrial technology and scientific research requires efficient THz detectors. Such detectors should be able to operate under various external conditions and conform to existing geometric constraints in the required application. Pyroelectric THz detectors are among the best candidates.

The venom of Habrobracon hebetor induces alterations in host metabolism.

The ability of parasitic wasps to manipulate a host's metabolism is under active investigation. Components of venom play a major role in this process. In the present work, we studied the effect of the venom of the ectoparasitic wasp Habrobracon hebetor on the metabolism of the greater wax moth host (Galleria mellonella).

Flame-Retardant Glass Fiber-Reinforced Epoxy Resins with Phosphorus-Containing Bio-Based Benzoxazines and Graphene.

This paper presents a study of the flammability and thermal decomposition products of glass fiber-reinforced epoxy resin (GFRER) with the addition of cardanol-based phosphorus-containing benzoxazine monomer (CBz) and graphene and their combinations in different proportions (up to 20 wt.%). The addition of CBz alone or in combination with graphene resulted in an increase in the limiting oxygen index (LOI) and self-extinguishing in the UL-94 HB test.

Study of oxygen transport in glassy polymers on a nanometer length scale utilizing the kinetic Monte Carlo simulations.

Diffusion-controlled deactivation of excited phenanthrene and oxidation of triplet aryl-nitrene by molecular oxygen were used to determine the energetics of oxygen jump rates in the set of glassy polymers: poly(methyl methacrylate), poly(n-butyl methacrylate), polycarbonate, polystyrene, and polysulfone. To interpret experimental results, a simple model based on the transition state theory of diffusion jump has been used. The kinetic Monte Carlo simulations of phenanthrene deactivation and nitrene oxidation were carried out in a cubic lattice that modeled a polymer matrix.

Glycyrrhetinic acid interaction with solvated and free electrons studied by the CIDNP and dissociative electron attachment techniques.

Electron transfer plays a crucial role in living systems, including the generation of reactive oxygen species (ROS). Oxygen acts as the terminal electron acceptor in the respiratory chains of aerobic organisms as well as in some photoinduced processes followed by the formation of ROS. This is why the participation of exogenous antioxidants in electron transfer processes in living systems is of particular interest.

The mutual lipid-mediated effect of the transmembrane domain of SARS-CoV-2 E-protein and glycyrrhizin nicotinate derivatives on the localization in the lipid bilayer.

Glycyrrhizinic acid (GA) is one of the active substances in licorice root. It exhibits antiviral activity against various enveloped viruses, for example, SARS-CoV-2. GA derivatives are promising biologically active compounds from perspective of developing broad-spectrum antiviral agents.

Involvement of bacteria in the development of fungal infections in the Colorado potato beetle.

Entomopathogenic fungi may interact with insects' symbiotic bacteria during infection. We hypothesized that topical infection with Beauveria bassiana may alter the microbiota of the Colorado potato beetle (CPB) and that these modifications may alter the course of mycoses. We used a model with two concentrations of conidia: (1) high concentration that causes rapid (acute) pathogenesis with fast mortality followed by bacterial decomposition of insects; (2) lower concentration that leads to prolonged pathogenesis ending in conidiation on cadavers.

Cobalt-Imidazole Complexes: Effect of Anion Nature on Thermochemical Properties.

A solvent-free method was proposed for the synthesis of hexaimidazolecobalt(II) nitrate and perchlorate complexes-[Co(CHN)](NO) and [Co(CHN)](ClO)-by adding cobalt salts to melted imidazole. The composition, charge state of the metal, and the structure of the resulting complexes were confirmed by elemental analysis, XPS, IR spectroscopy, and XRD. The study of the thermochemical properties of the synthesized complexes showed that [Co(CHN)](NO) and [Co(CHN)](ClO) are thermally stable up to 150 and 170 °C, respectively.

Quantification of Distributions of Local Proton Concentrations in Heterogeneous Soft Matter and Non-Anfinsen Biomacromolecules.

A new method to quantitatively analyze heterogeneous distributions of local proton densities around paramagnetic centers in unstructured and weakly structured biomacromolecules and soft matter is introduced, and its feasibility is demonstrated on aqueous solutions of stochastically spin-labeled polysaccharides. This method is based on the pulse EPR experiment ih-RIDME (intermolecular hyperfine relaxation-induced dipolar modulation enhancement). Global analysis of a series of RIDME traces allows for a mathematically stable transformation of the time-domain data to the distribution of local proton concentrations.

Toward New Horizons in Verdazyl-Nitroxide High-Spin Systems: Thermally Robust Tetraradical with Quintet Ground State.

High-spin organic tetraradicals with significant intramolecular exchange interactions have high potential for advanced technological applications and fundamental research, but examples reported to date exhibit limited stability and processability. In this work, we designed the first tetraradical based on an oxoverdazyl core and nitronyl nitroxide radicals and successfully synthesized it using a palladium-catalyzed cross-coupling reaction of an oxoverdazyl radical bearing three iodo-phenylene moieties with a gold(I) nitronyl nitroxide-2-ide complex in the presence of a recently developed efficient catalytic system. The molecular and crystal structures of the tetraradical were confirmed by single crystal X-ray diffraction analysis.

Self-assembly of spin-labeled antimicrobial peptides magainin 2 and PGLa in lipid bilayers.

The cationic antimicrobial peptides PGLa and magainin 2 (Mag2) are known for their antimicrobial activity and synergistic enhancement in antimicrobial and membrane leakage assays. Further use of peptides in combinatory therapy requires knowledge of the mechanisms of action of both individual peptides and their mixtures. Here, electron paramagnetic resonance (EPR), double electron-electron resonance (DEER, also known as PELDOR) and electron spin echo envelope modulation (ESEEM) spectroscopies were applied to study self-assembly and localization of spin-labeled PGLa and Mag2 in POPE/POPG membranes with a wide range of peptide/lipid ratios (P/L) from ∼1/1500 to 1/50.

The Impact of Long-Term Hypoxia on the Antioxidant Defense System in the Siberian Frog Rana amurensis.

The Siberian frog Rana amurensis has a uniquely high tolerance to hypoxia among amphibians, as it is able to withstand several months underwater with almost no oxygen (0.2 mg/liter) vs. several days for other studied species.

Primary photophysical and photochemical processes for cerium ammonium nitrate (CAN) in acetonitrile.

Cerium ammonium nitrate (CAN) is an important photolytic source of NO radicals in aqueous nitric acid solutions and in acetonitrile. In this work we performed the study of primary photochemical processes for CAN in acetonitrile by means of ultrafast TA spectroscopy and quantum chemical calculations. Photoexcitation of CAN is followed by ultrafast (< 100 fs) intersystem crossing; the vibrationally cooled triplet state decays to pentacoordinated Ce(III) intermediate and NO radical with the characteristic time of ca.