Search results for " Spectroscopy"

Polysaccharides from Pleurotus eryngii var. elaeoselini (Agaricomycetes), a New Potential Culinary-Medicinal Oyster Mushroom from Italy.

2020

Three water-soluble glucans (PELPS-A1, PELPS-A2, and PELPS-A3) purified from the hot water extract of the basidiomata of an edible mushroom Pleurotus eryngii var. elaeoselini by chromatography on DEAE-cellulose 32 and Sephadex G-100 column were found to consist of only D-glucose as monosaccharide constituent. Structural investigation was carried out by acid hydrolysis, periodate oxidation, and NMR experiments (1H-NMR, 13C-NMR, DQF-COSY, TOCSY, ROESY, HMQC, and HMBC). On the basis of these experiments, the structures of the repeating unit of the three isolated polysaccharides were established as follows: (1) PELPS-A1: {[→3)-α-D-Glcp-(1→]3→4)-α-D-Glcp-(1→2)-α-D-Glcp-(1→6)-α-D-Glcp-(1[→6)-β-D-…

Novel σ1 antagonists designed for tumor therapy: Structure – activity relationships of aminoethyl substituted cyclohexanes

2021

Abstract Depending on the substitution pattern and stereochemistry, 1,3-dioxanes 1 with an aminoethyl moiety in 4-position represent potent σ1 receptor antagonists. In order to increase the stability, a cyclohexane ring first replaced the acetalic 1, 3-dioxane ring of 1. A large set of aminoethyl substituted cyclohexane derivatives was prepared in a six-step synthesis. All enantiomers and diastereomers were separated by chiral HPLC at the stage of the primary alcohol 7, and their absolute configuration was determined by CD spectroscopy. Neither the relative nor the absolute configuration had a large impact on the σ1 affinity. The highest σ1 affinity was found for cis-configured benzylamines…

Rotational Raman spectroscopy of ethylene using a femtosecond time-resolved pump-probe technique.

2005

154309; Femtosecond Raman-induced polarization spectroscopy (RIPS) was conducted at low pressure (250 mb at 295 K and 400 mb at 373 K) in ethylene. The temporal signal, resulting from the beating between pure rotational coherences, was measured with a heterodyne detection. The temporal traces were converted to the frequency domain using a Fourier transformation and then analyzed thanks to the D2hTDS software (http://www.u-bourgogne.fr/LPUB/shTDS.html) dedicated to X2Y4 molecules with D2h symmetry. The effective Hamiltonian was expanded up to order 2, allowing the determination of five parameters with an rms of 0.017 cm(-1). Special care was taken in the precise modeling of intensities, taki…

Structure of SNX9 SH3 in complex with a viral ligand reveals the molecular basis of its unique specificity for alanine-containing class I SH3 motifs

2021

Class I SH3 domain-binding motifs generally comply with the consensus sequence [R/K]x0PxxP, the hydrophobic residue 0 being proline or leucine. We have studied the unusual 0 = Ala-specificity of SNX9 SH3 by determining its complex structure with a peptide present in eastern equine encephalitis virus (EEEV) nsP3. The structure revealed the length and composition of the n-Src loop as important factors determining specificity. We also compared the affinities of EEEV nsP3 peptide, its mutants, and cellular ligands to SNX9 SH3. These data suggest that nsP3 has evolved to minimize reduction of conformational entropy upon binding, hence acquiring stronger affinity, enabling takeover of SNX9. The R…

s-wave charmed baryon resonances from a coupled-channel approach with heavy quark symmetry

2009

We study charmed baryon resonances which are generated dynamically within a unitary meson-baryon coupled channel model that treats the heavy pseudoscalar and vector mesons on equal footing as required by heavy-quark symmetry. It is an extension of recent SU(4) models with t-channel vector meson exchanges to a SU(8) spin-flavor scheme, but differs considerably from the SU(4) approach in how the strong breaking of the flavor symmetry is implemented. Some of our dynamically generated states can be readily assigned to recently observed baryon resonances, while others do not have a straightforward identification and require the compilation of more data as well as an extension of the model to d-w…

Long-Range and Short-Range Structure of Proton-Conducting Y:BaZrO3

2011

Yttrium-doped barium zirconate (BZY) is the most promising candidate for proton-conducting ceramics and has been extensively studied in recent years. The detailed features of the crystal structure, both short-range and long-range, as well as the crystal chemistry driving the doping process, are largely unknown. We use very high resolution X-ray diffraction (HR-XRD) to resolve the crystal structure, which is very slightly tetragonally distorted in BZY, while the local environment around Zr4+ and Y3+ is probed with extended X-ray absorption fine structure (EXAFS), and the symmetry and vibrations are investigated by using Raman spectroscopy. It is found that barium zirconate shows some degree …

Application of time-resolved spectroscopy to concentration measurements in gas mixtures

2001

1296-2147; Concentration measurements using femtosecond Raman Induced Polarization Spectroscopy (RIPS) are performed in binary gas mixtures CO2-N2 and CO2-N2O at room temperature. The principle of these measurements is based on the nonlinear rotational time response of each molecular component of the mixture, The general form of this molecular response is a series of periodic transients with a period related to the rotational constant Be The relative strength of the individual responses allows an accurate determination of the concentration. Two techniques are presented using either two pulses (one pump and one probe) or three pulses (two pumps and one probe). (C) 2001 Academie des sciences/…

Cytotoxic drimane meroterpenoids from the Indonesian marine sponge Dactylospongia elegans

2017

Abstract Chemical investigation of the methanol extract of an Indonesian marine sponge Dactylospongia elegans (family Thorectidae) afforded two undescribed drimane meroterpenoidal metabolites, dactylospongenones G and H (1 and 2) together with thirteen known compounds (3–15) including pelorol, 5-epi-ilimaquinone, 5-epi-smenospongine, 5-epi-smenospongidine, nakijiquinone D, smenospongine C, isospongiaquinone, isosmenospongine, nakijiquinones A-C, G and 5-epi-nakijiquinone Q. The structures of the new metabolites were unambiguously determined by 1D and 2D NMR spectroscopy and by HRESIMS. All isolated compounds were assessed for their antimicrobial, antitubercular and cytotoxic activities. Sev…

High Pressure Liquid Chromatographic Analysis of Barbiturates in the Picomole Range by Fluorometry of Their DANS-Derivatives

1974

Determination of quality parameters of beers by the use of attenuated total reflectance-Fourier transform infrared spectroscopy

2005

Abstract The estimation of important quality parameters of beers, such as original and real extracts and alcohol content, has been evaluated by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) using a partial least square (PLS) calibration approach. Two sample populations, one consisting of 24 samples and other of 21 samples, obtained from the Spanish market and covering different types of beer were used. The first set was used for building and validating the model, whereas the second, measured 6 months after, was used for evaluating its robustness. The spectral range and the size of the calibration set and its suitability for building the PLS model have been …