Search results for " Magnetic resonance"

Lignans from Torreya jackii identified by stopped-flow high-performance liquid chromatography–nuclear magnetic resonance spectroscopy

1999

Abstract Coupled reversed-phase HPLC–NMR spectroscopy has been applied to the rapid detection and identification of plant metabolites of Torreya jackii , a species of Taxaceae. Analysis consisted of gradient HPLC elution and directly coupled 1 H NMR (500 MHz) spectroscopic detection in a stopped-flow mode. Seven lignans were detected and their structures were elucidated, based on their HPLC– 1 H NMR spectra and MS data. The structures were confirmed by isolation of the single components followed by conventional NMR measurements.

Music and Emotions in the Brain: Familiarity Matters

2011

The importance of music in our daily life has given rise to an increased number of studies addressing the brain regions involved in its appreciation. Some of these studies controlled only for the familiarity of the stimuli, while others relied on pleasantness ratings, and others still on musical preferences. With a listening test and a functional magnetic resonance imaging (fMRI) experiment, we wished to clarify the role of familiarity in the brain correlates of music appreciation by controlling, in the same study, for both familiarity and musical preferences. First, we conducted a listening test, in which participants rated the familiarity and liking of song excerpts from the pop/rock repe…

Frontocingular Dysfunction in Bulimia Nervosa when Confronted with Disease-specific Stimuli

2011

Objective Bulimia nervosa (BN) is characterized by dysregulation of impulse control, in other words, uncontrolled eating. Functional neuroimaging studies have been sparse and have used variable methodologies. Method Thirteen medication-free female BN patients and 13 female healthy controls were investigated by functional magnetic resonance imaging using a disease-specific food paradigm. Stimuli were rated after the scanning procedure. Results Bulimia nervosa patients showed increased fear ratings and a trend for increased disgust. Magnetic resonance imaging data of 10 BN patients could be analysed. Three BN patients had to be excluded from the analysis because of minimal blood oxygen level …

Secondary metabolites from the aerial parts of Cytisus villosus Pourr

2017

Phytochemical investigation of the aerial parts of Cytisus villosus Pourr. resulted in the isolation and characterization of a new isoflavan, (3S, 4S)-2′,4′-dihydroxy-3′-methoxy-6,7-methylenedioxyisoflavan- 4-ol (1), and a new monoterpene, (4R,6S)-4-hydroxy-2,2,6-trimethyl-9-oxabicyclo [4.2.1] non-1(8)-en-7-one (2), together with four known flavonoids: geinstein (3), chrysin (4), chrysin -7-O-β-D-glucopyranoside (5) and 2″-O-α-L-rhamnosylorientin (6). The structures of the new compounds were elucidated on the basis of extensive spectroscopic analysis, including 1D, 2D NMR ((1)H, (13)C, COSY, TOCSY, HMBC and HSQC) and HRESIMS. The absolute configurations of 1 and 2 were established by the co…

Alkaloids from the Sponge-Associated FungusAspergillussp.

2012

Seven new alkaloids including tryptoquivaline K (1) and fumiquinazolines K–P (2–7), bearing a rare 1-aminocyclopropane-1-carboxylic acid residue, together with six known compounds (8–13), were isolated from the fungus Aspergillus sp. obtained from the Mediterranean sponge Tethya aurantium. The structures of the new compounds were determined by extensive analysis by 1D and 2D NMR spectroscopy and mass spectrometry. The absolute configurations of tryptoquivaline K (1) and fumiquinazolines K and L (2, 3) were determined by TDDFT ECD calculations of their solution conformers, and the configurational assignment of the related fumiquinazolines M–P (4–7) was achieved by comparison of their ECD spe…

Optical rotatory dispersion and circular dichroism of poly-L-lactide. A reply to a letter by M. Goodman and M. D'alagni (1)

1967

VCD studies on cyclic peptides assembled from L-α-amino acids and a trans-2-aminocyclopentane- or trans-2-aminocyclohexane carboxylic acid.

2010

The increasing interest in peptidomimetics of biological relevance prompted us to synthesize a series of cyclic peptides comprising trans-2-aminocyclohexane carboxylic acid (Achc) or trans-2-aminocyclopentane carboxylic acid (Acpc). NMR experiments in combination with MD calculations were performed to investigate the three-dimensional structure of the cyclic peptides. These data were compared to the conformational information obtained by electronic circular dichroism (ECD) and vibrational circular dichroism (VCD) spectroscopy. Experimental VCD spectra were compared to theoretical VCD spectra computed quantum chemically at B3LYP/6-31G(d) density functional theory (DFT) level. The good agreem…

Lactones from the Sponge-Derived Fungus Talaromyces rugulosus.

2017

The marine-derived fungus Talaromyces rugulosus isolated from the Mediterranean sponge Axinella cannabina and cultured on solid rice medium yielded seventeen lactone derivatives including five butenolides (1–5), seven (3S)-resorcylide derivatives (6–12), two butenolide-resorcylide dimers (13 and 14), and three dihydroisocoumarins (15–17). Among them, fourteen compounds (1–3, 6–16) are new natural products. The structures of the isolated compounds were elucidated by 1D and 2D NMR (Nuclear Magnetic Resonance) spectroscopy as well as by ESI-HRMS (ElectroSpray Ionization-High Resolution Mass Spectrometry). TDDFT-ECD (Time-Dependent Density Functional Theory-Electronic Circular Dichroism) calcul…

Cytotoxic hydrophilic iminophosphorane coordination compounds of d8 metals. Studies of their interactions with DNA and HSA

2012

The synthesis and characterization of a new water-soluble N,N-chelating iminophosphorane ligand TPAN-C(O)-2-NC(5)H(4) (N,N-IM) (1) and its d(8) (Au(III), Pd(II) and Pt(II)) coordination complexes are reported. The structures of cationic [AuCl(2)(N,N-IM)]ClO(4) (2) and neutral [MCl(2)(N,N-IM)] M=Pd (3), Pt(4) complexes were determined by X-ray diffraction studies or by means of density-functional calculations. While the Pd and Pt compounds are stable in mixtures of DMSO/H(2)O over 4 days, the gold derivative (2) decomposes quickly to TPAO and previously reported neutral gold(III) compound [AuCl(2)(N,N-H)] 5 (containing the chelating N,N-fragment HN-C(O)-2-NC(5)H(4)). The cytotoxicities of co…

Quantitative microscopy of magnetic domains in Fe(100) by core-level x-ray photoelectron spectroscopy

2005

We present an experimental technique for imaging of magnetic domain patterns based on element-specific core-level photoemission using polarized soft-x-ray radiation. It is applied to the measurement of domain patterns at the Fe(100) surface and at the surface of polycrystalline Fe. Different from well established imaging techniques that use a photoemission electron microscope to measure the secondary electron intensity at the Fe absorption threshold, we have investigated the photoemission intensity contrast on the the Fe $2{p}_{3∕2}$ core level using circularly polarized x-ray light. The linear and circular dichroism characteristics of the identical domain pattern are extracted by linear co…