Search results for "1H"
showing 10 items of 1291 documents
Accurate classification of childhood brain tumours by in vivo H-1 MRS - A multi-centre study
2013
Aims: To evaluate the accuracy of single-voxel Magnetic Resonance Spectroscopy (1H-MRS) as a non-invasive diagnostic aid for pediatric brain tumours in a multi-national study. Our hypotheses are (1) that automated classification based on 1H-MRS provides an accurate non-invasive diagnosis in multi-centre datasets and (2) using a protocol which increases the metabolite information improves the diagnostic accuracy. Methods: 78 patients under 16 years old with histologically proven brain tumours from 10 international centres were investigated. Discrimination of 29 medulloblastomas, 11 ependymomas and 38 pilocytic astrocytomas was evaluated. Single-voxel MRS was undertaken prior to diagnosis (1.…
Complete 1H and 13C NMR assignments of clerodane diterpenoids of Salvia splendens.
2006
Unambiguous and complete assignments of 1H and 13C NMR chemical shifts for five clerodane diterpenes, four of them isolated from Salvia splendens (salviarin, splendidin and splenolides A and B) and one obtained by acetylation of splenolide A, are presented. The assignments are based on 2D shift-correlated [1H,1H–COSY, 1H,13C-gHSQC–1J(C,H) and 1H,13C-gHMBC-nJ(C,H) (n = 2 and 3)] and nuclear Overhauser effect (NOE) experiments. The conformation of the rings of these compounds is supported by the 3J(H,H) values and NOE results. Copyright © 2006 John Wiley & Sons, Ltd.
Synthesis, Characterization and Catalytic Activity of mesoporous Mn-MCM-41 materials
2011
MCM-41 has been synthesized at two different pH using cetyl-trimethylammonium bromide (CTAB) surfactant as template and adding the silica precursor to aqueous solutions containing CTAB. The obtained solids were calcined at 600 ◦C for 4 h. Mn-MCM-41 powders with different Mn/Si molar ratios were prepared using the incipient wetness method, followed by calcination at 550 ◦C for 5 h. At the end of the impregnation process the powders colour changed from white to brown whose intensity depends on manganese quantity. The materials characterization was performed by X-ray diffraction, N2 adsorption, 29Si Cross Polarization–Magic Angle Spinning NMR, and X-ray Photoelectron Spectroscopy. The effects …
Tetranitroresorcin[4]arene: synthesis and structure of a new stereoisomer
2009
The direct reaction between 2-nitroresorcinol and acetaldehyde in alkaline medium yields tetranitro-C1-resorcin[4]arene in a moderate 8.2% overall yield which was characterized by single crystal X-ray crystallography, 1H NMR spectroscopy and electrospray ionization mass spectrometry (ESI-MS). In solution and in the solid state, the product adopts a unique, thermally stable and unprecedented rcct-boat conformation.
Preparation and structural studies on diorganotin(IV) complexes of N-nitroso-N-phenylhydroxylaminates
2007
Abstract Diorganotin(IV)-complexes of the N -nitroso- N -phenylhydroxylaminates (hereinafter cupf), Et 2 Sn(cupf) 2 ( 1 ), Bu 2 Sn(cupf) 2 ( 2 ), {[Bu 2 Sn(cupf)] 2 O} 2 ( 3 ), t -Bu 2 Sn(cupf) 2 ( 4 ) and Oc 2 Sn(cupf) 2 ( 5 , 6 ) were prepared and characterised by FT-IR and Mossbauer spectroscopic measurements. The binding modes of the ligand were identified by FT-IR spectroscopy, and it was found that the ligand is coordinated in chelating or bridging mode to the organotin(IV) center. The 119 Sn Mossbauer and FT-IR studies support the formation of trans -O h ( 1 – 6 ) structures. The X-ray diffraction analysis of 4 revealed that the tin centre is in a skew-trapezoidal geometry defined by…
Combined proton NMR wideline and NMR relaxometry to study SOM-water interactions of cation-treated soils
2013
Abstract Focusing on the idea that multivalent cations affect SOM matrix and surface, we treated peat and soil samples by solutions of NaCl, CaCl2 or AlCl3. Water binding was characterized with low field 1H-NMR-relaxometry (20 MHz) and 1H wideline NMR spectroscopy (400 MHz) and compared to contact angles. From 1H wideline, we distinguished mobile water and water involved in water molecule bridges (WaMB). Large part of cation bridges (CaB) between SOM functional groups are associated with WaMB. Unexpectedly, 1H NMRrelaxometry relaxation rates suggest that cross-linking in the Al-containing peat is not stronger than that by Ca. The relation between percentage of mobile water and WaMB water in…
CCDC 960138: Experimental Crystal Structure Determination
2013
Related Article: Mainak Mitra, Julio Lloret-Fillol, Matti Haukka, Miquel Costas, Ebbe Nordlander|2014|Chem.Commun.|50|1408|doi:10.1039/C3CC47830K
CCDC 894411: Experimental Crystal Structure Determination
2013
Related Article: S.Fustero, P.Bello, J.Miro, M.Sanchez-Rosello, M.A.Maestro, J.Gonzalez, C.del Pozo|2013|Chem.Commun.|49|1336|doi:10.1039/c2cc37796a
Impact of the ΔPhe configuration on the Boc-Gly-ΔPhe-NHMe conformation: experiment and theory
2019
Conformational propensities of N-t-butoxycarbonyl-glycine-(E/Z)-dehydrophenylalanine N′-methylamides (Boc-Gly-(E/Z)-ΔPhe-NHMe) in chloroform were investigated by NMR and IR techniques. The low-temperature crystal structure of the E isomer was determined by single crystal X-ray diffraction and the experimental data were elaborated by theoretical calculations using DFT (B3LYP, M06-2X) and MP2 approaches. The β-turn tendencies for both isomers were determined in the gas phase and in the presence of solvent. The obtained results reveal that the configuration of ΔPhe residue significantly affects the conformations of the studied dehydropeptides. The tendency to adopt β-turn conformations is sign…