Magnetic Resonance in Chemistry最新文献

In our study, chemical investigation of the marine fungus Penicillium sp. led to the isolation of four isocoumarin derivatives, including two new compounds (1 and 2) and two known analogues (3 and 4). The structures of 1 and 2 were determined by comprehensive analysis of the 1D (¹H and ¹³C NMR spectra) and 2D NMR data (COSY, HSQC, HMBC, and NOESY spectra). The structure of 1 was confirmed by comparing the calculated and experimental ¹³C NMR data. Compounds 1 and 2 are isocoumarins that lack substitution at the C-5, C-6, and C-7 positions, a structural feature that is uncommon among this class of natural products. The current study enriched the chemical diversity of fungus-derived isocoumarin derivatives.

We report the nuclear magnetic resonance dispersion (NMRD) profile of superparamagnetic iron oxide nanoparticles (SPIONs) and compare the values obtained from its analysis with those from standard methods. Recorded at ¹H Larmor frequencies from 10 kHz to 600 MHz (0.23 mT to 14.1 T, static magnetic field), this profile covers water ¹H dynamics across a broad timescale encompassing all medically relevant magnetic field strengths in magnetic resonance imaging (MRI). This extensive coverage enables the extraction of accurate physicochemical parameters of the nanoparticles that dictate their efficiency (relaxivity). To support this approach, other conventional characterization methods, including TEM, DLS/zeta potential, and VSM, were employed and compared with the NMRD findings. To ensure robustness, the NMRD profiles were recorded at both 25°C and 37°C. Analysis of NMRD profiles, in conjunction with the appropriate theoretical model, successfully characterized SPIONs, yielding coherent parameters that compare favorably with those from conventional characterization methods.

The article reviews the electron paramagnetic resonance research carried out in India over the last three decades. After providing a broad picture of the number and type of publications pertaining to the period, studies on condensed matter physics topics such as manganites, high-Tc superconductors and water are spotlighted.

Spinocerebellar ataxia 12 (SCA12) is a progressive degenerative neurological disorder, primarily characterized by impaired coordination and balance. To investigate the correlation between proton (¹H) magnetic resonance spectroscopy (MRS) and structural imaging indices in patients with SCA12. T1-weighted MRI, DTI, and single voxel MRS point resolved spectroscopy (PRESS) in the left hemispheric cerebellum were acquired using a 3-T MR scanner in 40 SCA12 patients and 25 healthy controls. Correlations between metabolites, gray and white matter volume of lobules, fractional anisotropy (FA), and clinical, nonclinical, and genetic data were examined. Three machine learning algorithms (KNN, LDA, and SVM) were used to analyze the metabolic feature differences between SCA12 and HC groups. Significant decreases in choline (Cho [GPC (glycerophosphocholine) + PCh (phosphocholine)]) and N-acetyl aspartate (NAA) levels, along with increases in myo-inositol ratios to creatine, FA, and white matter volume values (p < 0.05), were observed in the cerebellum of the SCA12 group compared to healthy controls. Positive correlations were observed between NAA levels and cerebellar lobule volume, the SPM IQ score with the right crus II in the SCA12 group. The International Cooperative Ataxia Rating Scale (ICARS) score showed a negative correlation with white matter and specific cerebellar lobules. Disease duration and cytosine, adenine, and guanine (CAG) repeat length were negatively correlated with right lobule VIIIB, lobule IX, and left lobule X. Machine learning algorithms achieved an accuracy of over 95% in MRS data, and 88.89% in volumetric data. MRS, VBM, and DTI techniques reveal neuronal degeneration in SCA12 compared to healthy individuals.

The spin Hamiltonian parameters (SHPs) (g factors g_// and g_⊥ and hyperfine structure constants A_// and A_⊥) and their concentration (x) dependences for Cu²⁺ in xNaI·(30–x)·Na₂O·70B₂O₃ (5 ≤ x ≤ 25) glasses are theoretically investigated in a consistent way. The [CuO₆]¹⁰⁻ complexes are subject to the Jahn–Teller effect, leading to the relative elongations of about 7%. The concentration dependences of the SHPs are suitably attributed to the nonmonotonic piecewise relationships of cubic field parameter, covalency factor, relative tetragonal elongation ratio, and core polarization constant with NaI concentration x due to the modifications of local crystal fields and electron cloud distribution around impurity Cu²⁺. The calculated cubic field splittings E₁, g factors, and A_// at various concentrations x agree well with the measured results, and the values of corresponding A_⊥ are also predicted. The properties of optical and EPR spectra are discussed, and the microscopic mechanisms of the concentration dependences of the related quantities are also analyzed.

A chemical investigation of the 95% EtOH extract of Dendrobium nobile Lindl. led to the isolation of one new sesquiterpene component (1), together with one known compound (2). Its structure was completely and unambiguously assigned by 1D and 2D NMR spectra (¹H NMR, ¹³C NMR, HSQC, HMBC, COSY, and NOESY), and HR-ESI-MS spectroscopic analysis and the absolute configuration was confirmed by ECD calculation.

The hydroethanolic extract obtained from the seeds of Annona diversifolia Saff (Annonaceae) fruits was analyzed to obtain a new cycloheptapeptide, called papaucin (1) or cyclo(-Pro¹-Val²-Ile³-Thr⁴-Asn⁵-Leu⁶-Gly⁷-). Its molecular structure was determined using 1D and 2D NMR spectroscopic techniques (¹H, ¹³C, HSQC, COSY, HMBC, and TOCSY) and MALDI-TOF mass spectrometry. Additionally, the antiprotozoal activity was evaluated. Papaucin (1) showed moderate positive activity compared with in vitro assays of Entamoeba histolytica and Giardia lamblia, with IC₅₀ values of 63.07 and 67.62 μg mL⁻¹ respectively. On the other hand, in silico studies revealed a higher affinity of papaucin for the PFOR enzyme compared with metronidazole, as evidenced by a greater number of polar interactions. Regarding the ALR enzyme, papaucin also showed affinity, although at a binding site different from the main catalytic site. These results suggest that papaucin could exert its antiprotozoal effect through multiple mechanisms.