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H A Tajmir-Riahi

Publications and source records attributed to H A Tajmir-Riahi.

64 records · Page 4Linked to original sources
PubMed1988

Interaction of D-glucose with alkaline-earth metal ions. Synthesis, spectroscopic, and structural characterization of Mg(II)- and Ca(II)-D-glucose adducts and the effect of metal-ion binding on anomeric configuration of the sugar.

The interaction of D-glucose with the hydrated alkaline-earth metal halides has been studied in solution, and adducts of the type Mg(D-glucose)X2.4 H2O, Ca(D-glucose)X2.4 H2O, and Ca(D-glucose)2X2.4 H2O, where X = Cl- and Br-, have been isolated, and characterized by means of F.t.-i.r. and 1H-n.m.r. spectroscopy, X-ray powder diffraction, and molar conductivity measurements. Spectroscopic and other evidence suggested that the Mg(II) ion in the Mg(D-glucose)X2.4 H2O adducts six-coordinate, binding to a D-glucose molecule (possibly via O-1 and O-2 atoms) and to four H2O molecules, whereas, in the corresponding 1:1 Ca-D-glucose adduct, the Ca(II) ion is possibly seven-coordinate, binding to a sugar moiety (through the O-1, O-2, and other sugar donor atoms) and to four H2O molecules. In 1:2 Ca(D-glucose)2X2.4 H2O, the calcium ion may be eight-coordinate, binding to two D-glucose molecules (possibly via the O-1 and O-2 atoms of each sugar moiety) and to four H2O molecules. The strong, sugar H-bonding network is rearranged upon D-glucose adduct-formation, and the alpha-anomeric configuration is favored by these metal cation coordinations.

Calcium↗
PubMed1988

A laser Raman spectroscopic study of the interaction of the methylmercury cation with AMP, ADP and ATP.

The interaction of the CH3Hg+ cation with adenosine 5'-monophosphate, adenosine 5'-diphosphate, and adenosine 5'-triphosphate has been studied in aqueous solution at neutral pH by laser Raman spectroscopy. Metal binding is shown to occur preferentially at the N-1 ring position of adenine, with some indication of coordination to the N-7 site and substitution of a proton on the exocyclic NH2 group of the nucleic base. Binding of the cation to phosphate groups also occurs extensively, with both the -PO2-3 and -PO-2 groups. The equilibrium constants for the binding to the phosphate groups and for N-1 coordination are approx. 70 and 600 M-1, respectively.

Adenosine Diphosphate↗
PubMed1988

A laser Raman spectroscopic study of the interaction of calf-thymus DNA with Cu(II) and Pb(II) ions: metal ion binding and DNA conformational changes.

The interaction of calf-thymus DNA with Cu(II) and Pb(II) ions has been investigated in H2O and D2O solutions at physiological pH, using laser Raman spectroscopy. The results confirm the destabilizing effect of Cu2+ ions, which are shown to bind strongly to the guanine and cytidine bases, perturbing the A-T base pairs and disrupting the double-helical structure of DNA, whose conformation is markedly altered by these interactions. Earlier claims that Pb2+ ions destabilize DNA are not supported by the present study. These ions are found to interact only weakly with the nucleic bases, binding to the N7 position of the guanine bases and also interacting with the A-T pairs. Both types of ions are found to interact with the charged phosphate groups of DNA, although these sites are preferred over the nucleic bases by Pb2+ ions.

Copper↗
PubMed1987

Sugar interaction with biologically active cis-PtCl2(NH3)2 (anticancer) and its inactive trans isomer.

The interaction of D-glucuronic and D-gluconic acids with cis- and trans-PtCl2(NH3)2 (cisplatin and transplatin) has been investigated in aqueous solution and solid complexes of the type cis-[PtL(NH3)2]L.H2O and trans-[PtL2(NH3)2]L.H2O, where L = D-glucuronate or D-gluconate anions, are isolated and characterized by means of Fourier transform-infrared and 1H-NMR spectroscopy, and molar conductivity and X-ray powder diffraction measurements. Spectroscopic and other evidence indicated that the sugar anions bind monodentately in trans-[PtL2(NH3)2].H2O and bidentately in cis-[PtL(NH3)2]L.H2O complexes through the carboxylate oxygen atoms and other sugar donor groups. The strong sugar intermolecular hydrogen-bonding network is altered to that of the sugar-OH...NH3(H2O)...OH-sugar, upon platinum-ammine interaction. The D-glucuronate anion has the beta-anomer configuration both in the free salt and in these platinum-sugar complexes.

Cisplatin↗
PubMed1986

Sugar adducts with alkaline earth metal ions. Interaction of L-arabinose with Sr(II) and Ba(II) ions and the effects of metal ion binding on the sugar anomeric configurations.

The reaction between L-arabinose and hydrated Sr(II) or Ba(II) halide salts has been studied in H2O solution and adducts of the type M(L-arabinose)X(2).4H(2)O, where M = Sr(II) or Ba(II) and X = Cl- or Br- have been isolated and characterized by means of Fourier transform infrared spectroscopy, 1H-NMR spectroscopy, molar conductivity and X-ray powder diffraction measurements. Due to the marked spectral similarities with those of the structurally known Ca(L-arabinose)X2 . 4H2O (X= Cl- or Br-) compounds, the Sr(II) and the BA(II) ions are eight-coordinated, binding to two l-arabinose molecules via O1, O5 of the first and O3, O4 of the second sugar moiety and to four H2O molecules. 1H-NMR spectroscopy indicated that the free L-arabinose has the beta-anomer configuration in aqueous solution, whereas the alpha-anomer isomer is preferred by Mg(II), Ca(II), Sr(II) and Ba(II) ions, on complexation.

Journal Article↗
PubMed1986

Magnesium-sugar interaction. Synthesis, spectroscopic and structural characterization of Mg-sugar complexes containing beta-D-fructose.

The interaction between beta-D-fructose and hydrated magnesium salts has been studied and complexes of the type Mg(beta-D-fructose)Cl2.4H2O and Mg(beta-D-fructose)Br2.4H2O have been isolated and characterized. On the basis of comparisons of the spectroscopic and other chemical properties of several structurally known calcium-fructose compounds with those of the corresponding magnesium complexes, it is concluded that Mg2+ binds to two sugar moieties via O(2), O(3) of the first and O(4), O(5) of the second and to two water molecules, resulting in a six-coordinate geometry around the Mg2+. The strong sugar hydrogen-bonding network is rearranged upon sugar metallation and the sugar moiety shows the beta-anomer conformation in these magnesium-sugar complexes.

Journal Article↗
PubMed1986

Vitamin C interaction with cobalt-ammine cations. Synthesis, spectroscopic and structural characterization of cobalt-pentammine and cobalt-tetrammine sugar complexes containing L-ascorbate anion.

Interaction between [Co(NH3)5Cl]Cl2, [Co(NH3)4Cl2]Cl and L-ascorbic acid has been investigated in aqueous solution and solid complexes of the type [Co(NH3)5 ascorbate]Cl2 X H2O and [Co(NH3)4 ascorbate]Cl2 X H2O have been isolated and characterized by 13C-NMR, FT-IR and electron absorption spectroscopy. Spectroscopic and other evidence suggested that the sugar anion binds monodentately in the [Co(NH3)5 ascorbate]2+ cation via the ionized O3 oxygen atom and bidentately in [Co(NH3)4 ascorbate]2+ through the O1 and O4 oxygen atoms, resulting in a six-coordinate geometry around the Co(III) ion. The intermolecular sugar hydrogen-bonding network is perturbed upon sugar metalation and the sugar moiety shows a similar conformation to that of the sodium ascorbate compound in these series of cobalt-ammine complexes.

Ascorbic Acid↗
PubMed1985

Flexibility of DNA and RNA upon binding to different metal cations. An investigation of the B to A to Z conformational transition by Fourier transform infrared spectroscopy.

The interaction of DNA and RNA with Cu(II), Mg(II), [Co(NH3)6]3+ [Co(NH3)5Cl]2+ chlorides and, cis- and trans-Pt(NH3)2Cl2 (CIS-DDP, trans-DDP) has been studied by Fourier Transform Infrared (FT-IR) spectroscopy and a correlation between metal-base binding and conformational transitions in the sugar pucker has been established. It has been found that RNA did not change from A-form on complexation with metals, whereas DNA exhibited a B to Z transition. The marker bands for the A-form (C3'-endo-anti conformation) were found to be near 810-816 cm-1, while the bands at 825 and 690 cm-1 are marker bands for the B-conformation (C2'-endo, anti). The B to Z (C3'-endo. syn conformation) transition is characterized by the shift of the band at 825 cm-1 to 810-816 cm-1 and the shift of the guanine band at 690 cm-1 to about 600-624 cm-1.

Cations↗
PubMed1985

An FT-IR study of DNA and RNA conformational transitions at low temperatures.

Fourier Transform Infrared (FT-IR) spectra of solid samples of DNA and RNA obtained from freeze-drying at solid CO2 and liquid nitrogen temperatures, have been recorded and correlation between the conformational transitions and spectral changes is proposed. It is concluded that an equilibrium exists between A, B and Z conformations at low temperatures for the DNA molecule, which is temperature dependent, whereas the RNA molecule exhibits only the A conformation. The results have been compared with the metal-adducts of DNA and RNA, where one of the conformations is predominant. Marker infrared bands for the B conformer have been found to be the strong band at 825 cm-1 (sugar conformer mode) and a band with medium intensity at 690 cm-1 (guanine breathing mode). The A conformation showed characteristic bands at 810 and 675 cm-1. The B to Z conformational transition was characterized by the strong absorption bands near 820-810 cm-1 and at 665-600 cm-1.

Crystallization↗