Polynitroxides with varying numbers of nitroxide groups (one to four) derived from different aromatic core structures show intramolecular electron spin-spin coupling. The scope of this study is to establish an easy methodology for extracting structural, dynamical, and thermodynamical information from the EPR spectra of these polynitroxides which might find use as spin probes in complex systems, such as biological and host/guest systems, and as polarizing agents in dynamic nuclear polarization (DNP) applications. Density functional theory (DFT) calculations at the B3LYP/6-31G(d) level provided information on the structural details such as bond lengths and angles in the gas phase, which were compared with the single crystal X-ray diffraction data in the solid state. Polarizable continuum model (PCM) calculations were performed to account for solvent influences. The electron paramagnetic resonance (EPR) spectra of the polynitroxides in chloroform were analyzed in detail to extract information such as the percentages of different conformers, hyperfine coupling constants a, and rotational correlation times τ(c). The temperature dependence on the line shape of the EPR spectra gave thermodynamic parameters ΔH and ΔS for the conformational transitions. These parameters were found to depend on the number and relative positions of the nitroxide and other polar groups.
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Sci Rep
January 2025
Faculty of Biochemistry, Biophysics and Biotechnology, Department of Plant Physiology and Biochemistry, Jagiellonian University, Gronostajowa 7, 30-387, Kraków, Poland.
In this work a novel method for synthesis of 1,8-dihydroxynaphthalene melanin was presented, as well as the physicochemical properties, molecular structure, and characteristics of the pigment. The proposed synthesis protocol is simple and cost-effective with no enzymes or catalysts needed. The final product is not adsorbed on any surface, since the pigment is the result of autooxidation of 1,8-dihydroxynaphthalene.
View Article and Find Full Text PDFBiochem Biophys Res Commun
December 2024
Universidad Nacional de Córdoba, Facultad de Ciencias Exactas, Físicas y Naturales, Departamento de Química, Cátedra de Química Biológica, Córdoba, Argentina; CONICET, Instituto de Investigaciones Biológicas y Tecnológicas (IIByT). Córdoba, Argentina. Electronic address:
Monoterpenes (MTs), the major constituents of plant essential oils, cover a broad spectrum of biological activities through their interaction with biomembranes. MTs are highly hydrophobic substances with a net electrical dipole, but are not clearly amphipathic. As a result, they aggregate at increasing concentrations in aqueous media, and in membrane environments their behavior changes from dynamics modulators to disruptors.
View Article and Find Full Text PDFJ Hazard Mater
December 2024
Key Laboratory of Groundwater Resources and Environment, Ministry of Education, Jilin University, Changchun 130021, China; Jilin Provincial Key Laboratory of Water Resources and Water Environment, Jilin University, Changchun 130021, China. Electronic address:
This study systematically investigated the direct photoreduction of Cr(Ⅵ) in ice under simulated sunlight without external reductants. It was shown that the Cr(Ⅵ) photoreduction was observed only in ice at near-neutral pH values but not in aqueous solutions. Cr(Ⅵ) at an initial concentration of 10 μM was efficiently reduced by 75.
View Article and Find Full Text PDFEnviron Res
December 2024
U.S. Department of Energy, National Energy Technology Laboratory, Pittsburgh, PA, 15236-0940, USA.
Cadmium sulfide is widely employed in environmental catalysis due to its excellent catalytic behaviors. However, the inherent toxicity and leaching risk of CdS-based catalyst presents significant challenges for practical applications. This study explored the incorporation of CdS nanowires on the nitrogen-doped multi-wall carbon tubes (N-MWCNTs) substrate to minimize the leaching rate and mitigate the bio-toxicity by regulating the electron transfer process.
View Article and Find Full Text PDFChemistry
December 2024
Department of Chemistry, & Department of Bioscience & Biomedical Engineering, Indian Institute of Technology Bhilai, Durg, 491002, Chattisgarh, India.
The biotin-conjugated Fe(III) catecholate complex [Fe(BioL)], Fe(BioL) (BioLH=N-(3,4-dihydroxyphenethyl)-5-((3aS,4S,6aR)-2-oxohexahydro-1H-thieno[3,4-d]imidazol-4-yl)pentanamide) is reported as targeted magnetic resonance imaging (MRI) contrast agents (CAs) to increase the payload for early-stage imaging of tumours. The high spin state and octahedral coordination of the Fe(III) complex are confirmed by EPR spectra and DFT optimized structure, respectively. The overall formation constant (log K) of Fe(BioL) is determined as 45, which is higher than the known, more stable complex [Fe(EDTA)].
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