Search results for "N compounds"
showing 10 items of 203 documents
Water Structure Recovery in Chaotropic Anion Recognition: High-Affinity Binding of Dodecaborate Clusters to γ-Cyclodextrin
2015
Dodecaborate anions of the type B12X12(2-) and B12X11Y(2-) (X=H, Cl, Br, I and Y=OH, SH, NH3(+), NR3(+)) form strong (K(a) up to 10(6) L mol(-1), for B12Br12(2-)) inclusion complexes with γ-cyclodextrin (γ-CD). The micromolar affinities reached are the highest known for this native CD. The complexation exhibits highly negative enthalpies (up to -25 kcal mol(-1)) and entropies (TΔS up to -18.4 kcal mol(-1), both for B12I12(2-)), which position these guests at the bottom end of the well-known enthalpy-entropy correlation for CDs. The high driving force can be traced back to a chaotropic effect, according to which chaotropic anions have an intrinsic affinity to hydrophobic cavities in aqueous …
Tin(IV) catalyzed D-galacturonic acid anomerization
2008
A comparative kinetic study of anomerization between the four main forms (alpha/beta-pyranosides and alpha/beta-furanosides) of D-galacturonic acid (GalAH(2), 1) and tin(IV) complexed D-galacturonate ([Sn(CH(3))(2)(GalA)(H(2)O)(2)], 2) in D(2)O, is reported. Important differences are shown by pD vs. mutarotation rate profiles of 1 and 2. Coordination, in fact, causes: i) a spectacular increase of the rate due to kinetic template assistance of the carboxylic tail holding the metal in close proximity to the reactive centre and ii) a change in the dependence of the rate on the pD. Entropic and enthalpic factors contribute to the huge activation energy decrease in 2. Anomerization rates of the …
Anti-cancer activity of di- and tri-organotin(IV) compounds with D-(+)-Galacturonic acid on human tumor cells
2018
Abstract We have compared the anti-proliferative activity in vitro, of R2SnGala (1-3) [R = Me, n-Bu, Ph] and novel R3SnGala (4, 5) [R = Me, n-Bu] with D-(+)-Galacturonic acid [HGala; Galaq-, q = (2) and (1) for R2SnGala and R3SnGala, respectively] compounds, towards human tumor cell lines of intestinal carcinoma (HCT-116) and breast adenocarcinoma (MCF-7). The new synthesized 4 and 5 compounds were characterized, in solution, by 1H, 13C and 119Sn NMR, that showed that HGala acts as monoanionic moiety and evidenced the dynamic behavior of the compounds, due to inter-conversions involving the anomeric carbon atom of the ligand. Cell viability, apoptosis induction and cell cycle distribution w…
Antifungal activity and tautomeric cyclization equilibria of formylphenylboronic acids
2019
2-Formylphenylboronic acid and four isomeric fluoro-2-formylphenylboronic acids have been found active against a series of fungal strains: Aspergillus, Fusarium, Penicillium and Candida. The level of antifungal activity was evaluated by agar diffusion tests as well as the determination of minimum inhibitory concentrations (MICs) by serial dilution method. Among the tested compounds, 4-fluoro-2-formylphenylboronic acid - an analogue of the known antifungal drug Tavaborole (AN2690) - proved to be the most potent antifungal agent. The tautomeric equilibrium leading to the formation of 3-hydroxybenzoxaboroles as well as the position of the fluorine substituent were revealed to play a crucial ro…
Spectroelectrochemistry of cytochrome c and azurin immobilized in nanoporous antimony-doped tin oxide
2011
Stable immobilization of two redox proteins, cytochrome c and azurin, in a thin film of highly mesoporous antimony-doped tin oxide is demonstrated via UV-vis spectroscopic and electrochemical investigation.
Size-selective incorporation of DNA nanocages into nanoporous antimony-doped tin oxide materials.
2011
A conductive nanoporous antimony-doped tin oxide (ATO) powder has been prepared using the sol-gel method that contains three-dimensionally interconnected pores within the metal oxide and highly tunable pore sizes on the nanoscale. It is demonstrated that these porous materials possess the capability of hosting a tetrahedral-shaped DNA nanostructure of defined dimensions with high affinity. The tunability of pore size enables the porous substrate to selectively absorb the DNA nanostructures into the metal oxide cavities or exclude them from entering the surface layer. Both confocal fluorescence microscopy and solution FRET experiments revealed that the DNA nanostructures maintained their int…
Complexation of the potassium ion by diaza crown compounds in aqueous solutions
1988
The conductance behavior of potassium nitrate in water with and without 1,7,10,16-tetraoxa-4,13-diazacyclooctandecane[2.2] and 4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo-8.8.8-exacosane[2.2.2] macrocyclic ligands have been studied in order to analyze the complexation behavior of potassium cations in water. The absence of the complexation found in the [2.2] system is discussed in terms of the ligand structural features (presence of hydrogen bond donor and acceptor sites). The ion pair association constant of potassium cryptate as obtained from conductance measurements is also reported and discussed.
Complexation and Extraction of PAHs to the Aqueous Phase with a Dinuclear Pt II Diazapyrenium‐Based Metallacycle
2010
New palladium and platinum metallacycles have been synthesized by reaction between a 2,7-diazapyrenium-based ligand and Pd(II) and Pt(II) complexes. The inclusion complexes between the metallacycles and polycyclic aromatic hydrocarbons (PAHs) in CD(3)NO(2) and D(2)O were studied by NMR spectroscopy. The structures of the inclusion complexes of the Pt metallacycle as host with pyrene, phenanthrene, and triphenylene were confirmed by single crystal X-ray crystallography. The association constants between the Pt metallacycle and the selected PAHs were determined in CH(3)CN following the characteristic charge-transfer band displayed in their UV/Vis absorption spectrum. Although in aqueous solut…
Diorganotin(IV) N-acetyl-L-cysteinate complexes: synthesis, solid state, solution phase, DFT and biological investigations.
2009
Diorganotin(IV) complexes of N-acetyl-L-cysteine (H(2)NAC; (R)-2-acetamido-3-sulfanylpropanoic acid) have been synthesized and their solid and solution-phase structural configurations investigated by FTIR, Mössbauer, (1)H, (13)C and (119)Sn NMR spectroscopy. FTIR results suggested that in R(2)Sn(IV)NAC (R = Me, Bu, Ph) complexes NAC(2-) behaves as dianionic tridentate ligand coordinating the tin(IV) atom, through ester-type carboxylate, acetate carbonyl oxygen atom and the deprotonated thiolate group. From (119)Sn Mössbauer spectroscopy it could be inferred that the tin atom is pentacoordinated, with equatorial R(2)Sn(IV) trigonal bipyramidal configuration. In DMSO-d(6) solution, NMR spectr…
Tributyltin affects phagocytic activity of Ciona intestinalis hemocytes
1995
Organotin compounds have been used in marine anti-fouling paints as biocides. Because tunicates are vulnerable to these compounds in their natural habitats, we used Ciona intestinalis to establish an assay for phagocytosis in vitro of yeast by hemocytes after exposure to different concentrations (0.0015, 0.015, 0.15 and 1.5 microM) of four organotin compounds: tributyltin (TBT), triphenyltin (TPT), dibutyltin (DBT) and diphenyltin (DPT). To evaluate the phagocytic activity, we used a method based on fluorescence excitation of yeast pre-treated with eosin-Y. The percentage of phagocytosis decreased from 45.1 +/- 3.49 to 22.4 +/- 5.14 at 1.5 microM of TBT (P0.001); it was significantly reduce…