Search results for " nuclear magnetic resonance spectroscopy"
showing 10 items of 173 documents
Two-dimensional 1 H NMR spectra of ferricytochrome c 551 from Pseudomonas aeruginosa
1993
AbstractThe full assignment of 1H NMR signals of heme proton resonances of ferricytochrome c551 from Pseudomonas aeruginosa has been performed by means of 2D NMR experiments. This technique allows the complete and unequivocal assignment of all heme resonances, including methylene resonances of the propionic groups, directly implicated in the pH dependence of the redox properties of cytochrome c551.
Melatonin: Structural characterization of its non-enzymatic mono-oxygenate metabolite
2003
Oxidation of melatonin by Fenton reagents as well as with hypochlorous acid or oxoferryl hemoglobin has been investigated. Analysis of products by low resolution/mass spectra (MS), high resolution/MS, 1H-nuclear magnetic resonance (NMR), 13C-NMR, correlated spectroscopy (COSY) and heterocorrelated spectroscopy (HETCOR) 2D NMR reveals the formation of a single mono-oxygenated product under all conditions and unequivocally assigns the N-[2-(5-methoxy-2-oxo-2,3-dihydro-1H-indol-3-yl)-ethyl]-acetamide structure, which had not been previously considered.
Sodium ion distribution in the vitreous body
1996
We have studied the nuclear magnetic resonance (NMR) relaxation behavior, and thus the dynamic properties, of the sodium ion in the vitreous body at different temperatures. The 23Na NMR spectrum exhibits a resonance, the intensity of which accounts for an ion visibility of 100%. The 23Na longitudinal and transverse relaxation times, at all temperatures but the highest, present two components, suggesting that the sodium ions are present in two states of different mobility, whose populations are in slow exchange on the NMR time scale. The correlation times and quadrupole coupling constants for the two sodium pools have been derived. The faster relaxation of a fraction of the vitreal sodium ha…
Steroidal saponins from the fruits of Solanum torvum
2013
Abstract Seven steroidal glycosides have been isolated from the fruits of Solanum torvum Swartz. Their structures were established by 2D NMR spectroscopic techniques ( 1 H, 1 H-COSY, TOCSY, NOESY, HSQC, and HMBC) and mass spectrometry as (25 S )-26-(β- d -glucopyranosyloxy)-3-oxo-5α-furost-20(22)-en-6α-yl- O -β- d -xylopyranoside ( 1 ), (25 S )-26-(β- d -glucopyranosyloxy)-3-oxo-22α-methoxy-5α-furostan-6α-yl -O -β- d -xylopyranoside ( 2 ), (25 S )-26-(β- d -glucopyranosyloxy)-3β-hydroxy-22α-methoxy-5α-furostan-6α-yl- O -α- l -rhamnopyranosyl-(1 → 3)-β- d -glucopyranoside ( 3 ), (25 S )-3β-hydroxy-5α-spirostan-6α-yl- O -β- d -xylopyranoside ( 4 ), (25 S )-3-oxo-5α-spirostan-6α-yl- O -β- d -x…
An NMR Study of the Interaction of 15N-Labelled Bradykinin with an Antibody Mimic of the Bradykinin B2 Receptor
1997
An isotope-edited NMR study of the peptide hormone bradykinin (RPPGFSPFR) bound to the Fab fragment of a monoclonal antibody against bradykinin (MBK3) is reported. MBK3 was previously shown to provide a binding site model of the B2 bradykinin receptor [Haasemann, M., Buschko, J., Faussner, A., Roscher, A. A., Hoebeke, J., Burch, R. M. & Muller-Esterl, W. (1991) Anti-idiotypic antibodies bearing the internal image of a bradykinin epitope, J. Immunol. 147, 3882-3892]. Bradykinin was obtained in a uniformly 15N-labelled form using recombinant expression of a fusion protein consisting of the glutathione-binding domain of glutathione S-transferase fused to residues 354-375 of the high-molecular-…
Squarroside A, a biologically active triterpene saponin from Acanthophyllum squarrosum.
1993
A new bioactive saponin has been isolated from the roots of Acanthophyllum squarrosum. Based on spectroscopic data, especially direct and long-range heteronuclear 2D NMR analysis, and on chemical transformations, the structure of this new compound was elucidated as 3-O-beta-D-galactopyranosyl-(1--2)-[beta-D-xylopyranosyl-(1--3)]-beta- D-glucuronopyranosyl gypsogenin 28-O-beta-D-xylopyranosyl-(1--4)-alpha-L- rhamnopyranosyl-(1--2)-[alpha-L-arabinofuranosyl-(1--3)]-beta-D-4-O- acetylfucopyranoside for which we proposed the name squarroside A. This molecule showed a concentration dependent immunomodulatory effect in the in vitro lymphocyte transformation test.
Triterpene Saponins from Tupidanthus calyptratus
2001
Five new bisdesmosidic saponins (1--5) were isolated from the aerial parts of Tupidanthus calyptratus. Their structures were determined by (1)H--(1)H correlation spectroscopy (COSY, TOCSY, ROESY) and (1)H--(13)C correlation (HSQC, HMBC) NMR experiments, FABMS, and chemical data.
Structure and cytotoxicity of steroidal glycosides from Allium schoenoprasum
2013
Abstract A phytochemical analysis of the whole plant of Allium schoenoprasum , has led to the isolation of four spirostane-type glycosides ( 1 – 4 ), and four known steroidal saponins. Their structures were elucidated mainly by 2D NMR spectroscopic analysis and mass spectrometry as (20 S ,25 S )-spirost-5-en-3β,12β,21-triol 3- O -α- l -rhamnopyranosyl-(1 → 2)-β- d -glucopyranoside ( 1 ), (20 S ,25 S )-spirost-5-en-3β,11α,21-triol 3- O -α- l -rhamnopyranosyl-(1 → 2)-β- d -glucopyranoside ( 2 ), laxogenin 3- O -α- l -rhamnopyranosyl-(1 → 2)-[β- d -glucopyranosyl-(1 → 4)]-β- d -glucopyranoside ( 3 ), and (25 R )-5α-spirostan-3β,11α-diol 3- O -β- d -glucopyranosyl-(1 → 3)-[β- d -glucopyranosyl-…
Cytotoxic steroidal glycosides from Allium flavum.
2014
Abstract Three new spirostane-type glycosides ( 1 – 3 ) were isolated from the whole plant of Allium flavum . Their structures were elucidated mainly by 2D NMR spectroscopic analysis and mass spectrometry as (20 S ,25 R )-2α-hydroxyspirost-5-en-3β-yl O -β- d -xylopyranosyl-(1 → 3)-[β- d -galactopyranosyl-(1→2)]-β- d -galactopyranosyl-(1→4)-β- d -galactopyranoside ( 1 ), (20 S ,25 R )-2α-hydroxyspirost-5-en-3β-yl O -β- d -xylopyranosyl-(1 → 3)-[β- d -glucopyranosyl-(1→2)]-β- d -galactopyranosyl-(1→4)-β- d -galactopyranoside ( 2 ), and (20 S ,25 R )-spirost-5-en-3β-yl O -α- l -rhamnopyranosyl-(1 → 4)-[β- d -glucopyranosyl-(1→2)]-β- d -glucopyranoside ( 3 ). The three saponins were evaluated f…
In Vitro–In Vivo Fluctuation Spectroscopies
2010
Fluorescence correlation spectroscopy (FCS) was first developed for biophysical studies in analogy with photon scattering correlation spectroscopy. Although it is mainly devoted to the study of freely diffusing particles, FCS is actually able to discern between different kinds of motions, such as diffusion, anomalous diffusion, or drift motions. The frontier application of FCS nowadays is in medical studies both within cells and on the cell membranes, and in the investigation of single molecules in solid matrices. In this field, FCS originated also image correlation spectroscopy methods. The whole field can be unified under the name of fluorescence fluctuation spectroscopy (FFS). We present…