Search results for "molecular conformation"
showing 10 items of 376 documents
Synthesis, Absolute Configuration, and Bacterial Mutagenicity of the 8 Stereoisomeric Vicinal Diol Epoxides at the Terminal Benzo Ring of Carcinogeni…
2011
The synthesis of the 8 possible stereoisomeric diol epoxides (DEs) at the terminal benzo ring of carcinogenic dibenz[a,h]anthracene (DBA) is reported. trans-3,4-Dihydroxy-3,4-dihydro-DBA (1) afforded the 4 bay region DEs: the enantiomeric pairs of the anti diastereomers (+)-3/(-)-3 and of the syn diastereomers (-)-4/(+)-4, respectively. trans-1,2-Dihydroxy-1,2-dihydro-DBA (2) served as precursor of the 4 reverse DEs: the enantiomeric pairs of the anti diastereomers (+)-5/(-)-5 and of the syn diastereomers (-)-6/(+)-6, respectively. The transformation of the olefinic double bond in the enantiomeric trans-dihydrodiols to epoxides was achieved by either (i) oxidation with m-chloroperoxybenzoic…
Plasmonic Focusing Reduces Ensemble Linewidth of Silver-Coated Gold Nanorods
2008
Silver coating gold nanorods reduces the ensemble plasmon line width by changing the relation connecting particle shape and plasmon resonance wavelength. This change, we term "plasmonic focusing", leads to less variation of resonance wavelengths for the same particle size distribution. We also find smaller single particle linewidth comparing resonances at the same wavelength but show that this does not contribute to the ensemble linewidth narrowing.
Structure, stability, and fragmentation of sodium bis(2-ethylhexyl)sulfosuccinate negatively charged aggregates in vacuo by MD simulations.
2014
Negatively charged supramolecular aggregates formed in vacuo by n bis(2-ethylhexyl)sulfosuccinate (AOT(-)) anions and n + n(c) sodium counterions (i.e., [AOT(n) Na(n+nc)](nc)) have been investigated by molecular dynamics (MD) simulations for n = 1 to 20 and n(c) = -1 to -5. By comparing the maximum excess charge values of negatively and positively charged AOTNa aggregates, it is found that the charge storage capability is higher for the latter systems, the difference decreasing as the aggregation number increases. Statistical analysis of physical properties like gyration radii and moment of inertia tensors of aggregates provides detailed information on their structural properties. Even for …
Synthesis, electrochemical and theoretical studies of the Au(i)-Cu(i) heterometallic clusters bearing ferrocenyl groups
2009
Treatment of the polymeric alkynyl compounds (AuC2R)n (R = Fc, C6H4Fc; Fc = ferrocenyl) with the diphosphine PPh2C6H4PPh2 gave complexes (RC2Au)PPh2C6H4PPh2(AuC2R) (1, R = Fc; 2, R = C6H4Fc) with end-capped ferrocenyl groups. The reactions of 1 or 2 with Cu(NCMe)4PF6 result in formation of the heterotrimetallic aggregates [{Au3Cu2(C2R)6}Au3(PPh2C6H4PPh2)3](PF6)2 (3, R = Fc; 4, R = C6H4Fc), which consist of the alkynyl clusters [Au3Cu2(C2R)6]−“wrapped” by the cationic [Au3(PPh2C6H4PPh2)3]3+“belt”. The novel compounds were characterized by NMR spectroscopy and ESI-MS measurements. The solid state structure of 3 is reported. Electrochemical properties of the complexes 1–4 have been studied. Th…
Entrapment of amino acids in gas phase surfactant assemblies: The case of tryptophan confined in positively charged (1R,2S)-dodecyl (2-hydroxy-1-meth…
2017
The ability of positively charged aggregates of the surfactant (1R,2S)‐dodecyl (2‐hydroxy‐1‐methyl‐2‐phenylethyl))dimethylammonium bromide (DMEB) to incorporate D-tryptophan or L-tryptophan in the gas phase has been investigated by electrospray ion mobility mass spectrometry (ESIâIMâMS). Strongly impacted by the pH of the electrosprayed solutions, both protonated (T+) and deprotonated (T-) tryptophan are effectively included into the aggregates, whereas, tryptophan in zwitterionic (T0) form is practically absent in singly charged DMEB aggregates but can be found in multiply charged ones. The ability to incorporate tryptophan increases with the aggregation number and charge state of aggr…
Isolated glyoxylic acid-water 1:1 complexes in low temperature argon matrices
2015
Abstract The 1:1 hydrogen bonded complexes between glyoxylic acid (GA) and water are studied in low temperature argon matrices. Four different complex structures were found in deposited matrices. The lowest energy conformer (T1) of GA was found to form complex, where the water molecule was attached to the opposite side of the intramolecular hydrogen bond in the molecule (T1B). Interestingly, this complex was estimated to be +8.0 kJ mol −1 higher in energy than the most stable structure (T1A), where the water is inserted into the internal hydrogen bond, and also found in solid argon but in smaller abundance. For the second-lowest energy conformer of GA (T2), the two lowest-energy complex str…
Rhenium(I) and platinum(II) complexes with diimine ligands bearing acidic phenol substituents: hydrogen-bonding, acid-base chemistry and optical prop…
2010
Tricarbonylchloro-rhenium(i) (1-4) and catecholato-platinum(ii) complexes (6, 7) of diimine ligands bearing phenol and O-protected phenol substituents have been prepared and fully characterised including single crystal structure analyses of 1, 4 and 7. The redox behaviour of the catecholato platinum(ii) complexes 6 and 7 has been probed by cyclic voltammetry, preparative oxidation and EPR spectroscopy (6˙(+), 7˙(+)). Reversible deprotonation of the hydroxy substituted complexes 1, 3 and 6 to 1(-), 3(-) and 6(-) resulted in significant changes in their electronic spectra. The luminescence properties of the diamagnetic complexes have been investigated using emission spectroscopy. DFT and TD-D…
Effect of T-R conformational change on sickle-cell hemoglobin interactions and aggregation
2004
We compare the role of a conformational switch and that of a point mutation in the thermodynamic stability of a protein solution and in the consequent propensity toward aggregation. We study sickle-cell hemoglobin (HbS), the beta6 Glu-Val point mutant of adult human hemoglobin (HbA), in its R (CO-liganded) conformation, and compare its aggregation properties to those of both HbS and HbA in their T (unliganded) conformation. Static and dynamic light scattering measurements performed for various hemoglobin concentrations showed critical divergences with mean field exponents as temperature was increased. This allowed determining spinodal data points T(S)(c) by extrapolation. These points were …
Acylated oleanane-type saponins from Ganophyllum giganteum
2014
Abstract Five oleanane-type saponins , 3- O -β- D -glucuronopyranosylzanhic acid 28- O -β- D -xylopyranosyl-(1→3)-[α- L -rhamnopyranosyl-(1→2)]-(4- O -acetyl)-β- D -fucopyranosyl ester ( 1 ), 3- O -β- D -glucopyranosylzanhic acid 28- O -β- D -xylopyranosyl-(1→3)-[α- L -rhamnopyranosyl-(1→2)]-(4- O -acetyl)-β- D -fucopyranosyl ester ( 2 ), zanhic acid 28- O -β- D -xylopyranosyl-(1→3)-[α- L -rhamnopyranosyl-(1→2)]-(4- O -acetyl)-β- D -fucopyranosyl ester ( 3 ), zanhic acid 28- O -α- L -rhamnopyranosyl-(1→2)-4- O -[(3′-hydroxy-2′-methyl-butyroyloxy)-3-hydroxy-2-methyl-butyroyloxy]-β- D -fucopyranosyl ester ( 4 ), medicagenic acid 28- O -α- L -rhamnopyranosyl-(1→2)-4- O -[(3′-hydroxy-2′-methyl-…
Effects of two-carbon bridge region methoxylation of benztropine: discovery of novel chiral ligands for the dopamine transporter
2001
6-Methoxylated and 8-oxygenated benztropines were prepared and evaluated for their DAT and SERT activity (binding and uptake inhibition). Methoxylation at the two-carbon bridge of benztropine produced a novel class of potent and selective DAT ligands. An interesting enantioselectivity was also observed for this new class of chiral benztropines. The inactivity of the 8-oxygenated analogues seems to point out that, unlike cocaine and its analogues, interactions of benztropine ligands with DAT may be strongly governed by the nitrogen atom.