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METAL-COMPLEX FORMATION ON THE SURFACE OF AMORPHOUS ALUMINUM HYDROXIDE .4. INTERACTION OF OXOVANADIUM(IV) AND VANADATE(V) WITH ALUMINUM HYDROXIDE IN THE PRESENCE OF SUCCINIC, MALIC AND 2-MERCAPTOSUCCINIC ACIDS
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EFFECT OF THE LIGAND STRUCTURE ON THE FORMATION OF COPPER(II) COMPLEXES ON THE SURFACE OF AMORPHOUS ALUMINUM HYDROXIDE IN THE PRESENCE OF 2,3-DIAMINOPROPIONIC AND 2,4-DIAMINOBUTYRIC ACIDS
No full textANCHORING OF COPPER(II)-DIPEPTIDE COMPLEXES TO THE SURFACE OF AMORPHOUS ALUMINUM HYDROXIDE
No full textCopper(II) complexes are formed by dipeptides on the surface of aluminium hydrous oxide upon simultaneous adsorption of metal ion and ligands from aqueous solution; the complexes are effectively anchored to the surface through binding of carboxylate groups to aluminium atoms
METAL-COMPLEX FORMATION ON THE SURFACE OF AMORPHOUS ALUMINUM HYDROXIDE .2. COPPER(II) COMPLEXES WITH PYRIDINEDICARBOXYLIC ACIDS
No full textMETAL-COMPLEX FORMATION ON THE SURFACE OF AMORPHOUS ALUMINUM HYDROXIDE .5. INTERACTION OF COPPER(II) WITH ALUMINUM HYDROXIDE IN THE PRESENCE OF ORTHO-TYROSINE, META-TYROSINE AND PARA-TYROSINE AND DOPA
No full textMETAL-COMPLEX FORMATION ON THE SURFACE OF AMORPHOUS ALUMINUM HYDROXIDE .3. COPPER(II) COMPLEXES OF O-PHOSPHO-L-SERINE AND O-PHOSPHO-L-TYROSINE
No full textNoncovalent interactions in high-performance liquid chromatography enantioseparations on polysaccharide-based chiral selectors
No full textDesigned more than thirty years ago in order to improve and maximize the discrimination capability of native polysaccharides, cellulose- and amylose-based selectors have shown excellent and unequalled performances for the enantioseparation of chiral compounds. The successful story of these chiral selectors relies on a multi-site high-ordered chiral platform which is held up by intramolecular hydrogen bonds (HBs), and makes the polymer able to host and discriminate enantiomers. In this environment, both achiral and stereoselective intermolecular noncovalent interactions play a pivotal role, and HBs, halogen bonds (XBs), dipole-dipole, π-π stacking, steric repulsive, and van der Waals interactions underlie adsorption process and formation of transient diastereomeric assemblies between the polymer and the enantiomer pair. In the last decades, advances in computational chemistry and spectroscopic techniques have improved knowledge of noncovalent interactions, contributing to decode their functions in chemical systems. Significantly, over time the growing interplay between experimental and theoretical approaches has contributed to unravel intermolecular forces underlying selector-selectand association and to understand recognition patterns. On this basis, this review summarizes seminal and representative studies dealing with noncovalent interactions that function in HPLC enantioseparations promoted by cellulose benzoates and phenylcarbamates of amylose and cellulose. The importance of integrating theoretical and experimental approaches to profile mechanisms and interaction patterns is highlighted by discussing focused case studies. In particular, the advantageous utilization of electrostatic potential (V) analysis and molecular dynamics (MD) simulations in this field is evidenced. A systematic compilation of all published literature has not been attempted
Electron paramagnetic resonance studies and effects of vanadium in Saccharomyces cerevisiae
No full textVanadium uptake by whole cells and isolated cell walls of the yeast Saccharomyces cerevisiae was studied. When orthovanadate was added to wild-type S. cerevisiae cells growing in rich medium, growth was inhibited as a function of the VO4(3-) concentration and the growth was completely arrested at a concentration of 20 mM of VO4(3-) in YEPD. Electron paramagnetic resonance (EPR) spectroscopy was used to obtain structural and dynamic information about the cell-associated paramagnetic vanadyl ion. The presence of EPR signals indicated that vanadate was reduced by whole cells to the vanadyl ion. On the contrary, no EPR signals were detected after interaction of vanadate with isolated cell walls. A 'mobile' and an 'immobile' species associated in cells with small chelates and with macromolecular sites, respectively, were identified. The value of rational correlation time tau r indicated the relative motional freedom at the macromolecular site. A strongly 'immobilized' vanadyl species bound to polar sites mainly through coulombic attractions was detected after interaction of VO2+ ions with isolated cell walls
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