Search results for "two-dimensional"
showing 10 items of 350 documents
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…
Genes coding for intermediate filament proteins closely related to the hagfish "thread keratins (TK)" alpha and gamma also exist in lamprey, teleosts…
2005
The "thread keratins (TK)" alpha and gamma so far have been considered highly specialized intermediate filament (IF) proteins restricted to hagfish. From lamprey, we now have sequenced five novel IF proteins closely related to TKalpha and TKgamma, respectively. Moreover, we have detected corresponding sequences in EST and genomic databases of teleosts and amphibians. The structure of the TKalpha genes and the positions of their deduced amino acid sequences in a phylogenetic tree clearly support their classification as type II keratins. The genes encoding TKgamma show a structure typical for type III IF proteins, whereas their positions in phylogenetic trees favor a close relationship to the…
Intermediate filament protein profiles of human testicular non-seminomatous germ cell tumors: correlation of cytokeratin synthesis to cell differenti…
1991
Abstract The patterns of cytoskeletal differentiation were studied in 20 testicular non-seminomatous germ cell tumors by immunohistochemistry, using diverse monoclonal antibodies specific for different intermediate filament (IF) proteins and for desmoplakin. Immuno-fluorescence and immunoperoxidase methods on both formalin-fixed and frozen tissues were applied, in some cases together with a gel electrophoretic analysis of IF proteins. The tumors examined included embryonal carcinoma (EC), endodermal sinus tumor (EST), choriocar-cinoma and teratoma. Nine of the tumors were composed of only one histological type, the others showed mixed components. Cytokeratins 8 and 18 were identified in all…