Search results for "two-dimensional"
showing 10 items of 350 documents
Laser spectroscopy and the properties of light nuclei near the neutron drip line
1993
The interesting nuclear structure phenomena observed in some light nuclei at the neutron drip line suggest the measurement of basic ground state properties such as spins, magnetic moments and electric quadrupole moments. Here it will be discussed what experiments are presently feasable using laser spectroscopy. For the outstanding example of a “halo” nucleus,11Li, the development of a technique combining β-asymmetry detected optical pumping in a fast beam with NMR spectroscopy has yielded pertinent results, the most recent of which is an experimental value of the nuclear quadrupole moment.
Two-dimensional single- and multiple-quantum correlation spectroscopy in zero-field nuclear magnetic resonance.
2020
We present single- and multiple-quantum correlation $J$-spectroscopy detected in zero ($<\!\!1$~$\mu$G) magnetic field using a \Rb vapor-cell magnetometer. At zero field the spectrum of ethanol appears as a mixture of \carbon isotopomers, and correlation spectroscopy is useful in separating the two composite spectra. We also identify and observe the zero-field equivalent of a double-quantum transition in ${}^{13}$C$_2$-acetic acid, and show that such transitions are of use in spectral assignment. Two-dimensional spectroscopy further improves the high resolution attained in zero-field NMR since selection rules on the coherence-transfer pathways allow for the separation of otherwise overlappi…
Prognostic value of nuclear matrix protein expression in localized prostate cancer.
2012
The aim of the study was to correlate nuclear matrix (NM) protein expression profiles with the risk of PSA progression or death in early prostate cancer (PCa).High-resolution two-dimensional gel electrophoresis (2D-PAGE) was used to identify tumor-associated NM proteins in the PCa specimens obtained from 94 patients. The association between the expression of each protein and the probability of PSA progression or death was studied through univariate analysis. Unsupervised hierarchical clustering analysis was then used to generate patient clusters showing comparable outcomes by including the proteins that were predictive at univariate analysis. PSA-free and overall survival curves relative to…
Di-n-butyltin oxide as a chemical carbon dioxide capturer
2010
Abstract Several synthetic routes to the decakis(di-n-butyltin(IV)) oxocluster, (n-Bu2SnO)6[(n-Bu2SnOCH3)2(CO3)]2 (1), a diorganotin compound previously shown to belong to the class of organotins able to store carbon dioxide, as well as its reactivity toward dimethyl carbonate (DMC), are described. The synthetic route from n-Bu2SnO and DMC was applied for the preparation of the ethoxy analogue of 1, oxocluster 2, using diethyl carbonate. The structural relationship connecting cluster 1, with its precursor PRE-1 isolated from recycling experiments and n-Bu2SnO is discussed. For this purpose, the reactivity of PRE-1 with trifluoromethanesulfonic acid was investigated in order to trace structu…
Parallel simulation of dense two-dimensional polymer systems
1990
Abstract We present a parallel algorithm for the simulation of dense lattice polymer systems. The algorithm will be given for a two-dimensional system although the algorithm can be generalized to higher dimensions. We discuss timing results and applications.
Single Peptide Backbone Surrogate Mutations to Regulate Angiotensin GPCR Subtype Selectivity
2020
Mutating the side-chains of amino acids in a peptide ligand, with unnatural amino acids, aiming to mitigate its short half-life is an established approach. However, it is hypothesized that mutating specific backbone peptide bonds with bioisosters can be exploited not only to enhance the proteolytic stability of parent peptides, but also to tune its receptor subtype selectivity. Towards this end, four [Y]6-Angiotensin II analogues are synthesized where amide bonds have been replaced by 1,4-disubstituted 1,2,3-triazole isosteres in four different backbone locations. All the analogues possessed enhanced stability in human plasma in comparison with the parent peptide, whereas only two of them a…
Steroidal saponins from Dioscorea preussii.
2014
Abstract Three new steroidal saponins, named diospreussinosides A–C (1–3), along with two known ones (4, 5) were isolated from rhizomes of Dioscorea preussii. Their structures were elucidated mainly by 1D and 2D NMR spectroscopic analysis and mass spectrometry as (25S)-17α,25-dihydroxyspirost-5-en-3β-yl-O-α- l -rhamnopyranosyl-(1 → 4)-α- l -rhamnopyranosyl-(1 → 4)-β- d -glucopyranoside (1), (25S)-17α,25-dihydroxyspirost-5-en-3β-yl-O-α- l -rhamnopyranosyl-(1 → 4)-α- l -rhamnopyranosyl-(1 → 4)-[α- l -rhamnopyranosyl-(1 → 2)]-β- d -glucopyranoside (2), and (24S,25R)-17α,24,25-trihydroxyspirost-5-en-3β-yl-O-α- l -rhamnopyranosyl-(1 → 4)-α- l -rhamnopyranosyl-(1 → 4)-[α- l -rhamnopyranosyl-(1 → …
Indole alkaloids from the coprophilous fungus Aphanoascus fulvescens
2019
Abstract The Ascomycete fungus Aphanoascus fulvescens isolated from goose dung was investigated for its secondary metabolites, yielding five new indole alkaloids okaramines V–Z (1–5) and eleven known derivatives (6–16). Their structures were determined by 1D, 2D NMR spectra and HRMS data. Compounds 6, 8, 11 and 12 showed significant to moderate cytotoxicity against the mouse lymphoma cell line L5178Y with IC50 values ranging from 4.0 to 14.7 μM. Preliminary structure-activity relationships are discussed.
Secondary metabolites from the roots of Paronychia chionaea
2011
Two novel secondary metabolites, compounds (1–2) were isolated from the roots of Paronychia chionaea. On the basis of spectroscopic data including 1D and 2D NMR experiments (COSY, TOCSY, HSQC, and HMBC), and mass spectroscopy, their structures were established as 6- C-[α-L-arabinopyranosyl-(1→2)-β-D-glucopyranosyl]-7- O-[β-D-glucopyranosyl]-luteolin 3′-methyl ether (1), and 2-(methoxy)-2-(3,5-dimethoxy 4-hydroxyphenyl)-ethane-1,2-diol 1- O-β-D-glucopyranoside (2).
Steroidal saponins from Dracaena marginata
2013
Three new steroidal saponins and ten known ones were isolated from the bark of Dracaena marginata, along with two known steroidal saponins from the roots. Their structures were elucidated on the basis of extensive 1D and 2D NMR experiments and mass spectrometry as (25R)-26-(beta-D-glucopyranosyloxy)3beta,22alpha-dihydroxyfurost-5-en-1beta-yl O-alpha-L-rhamnopyranosyl-(1 --> 2)-[alpha-L-rhamnopyranosyl-(1 --> 4)]-beta-D-glucopyranoside (1), (25R)-26-(beta-D-glucopyranosyloxy)-3beta,22alpha-dihydroxyfurost-5-en-1beta-yl O-alpha-L-rhamnopyranosyl-(1 --> 2)-4-O-sulfo-alpha-L-arabinopyranoside (2), and (25S)-3beta-hydroxyspirost-5-en-1beta-yl O-alpha-L-rhamnopyranosyl-(1 --> 2)-4-O-sulfo-alpha-L…