title: Spectroscopic investigation of new water soluble Mn(II)(2) and Mg(II)(2) complexes for the substrate binding models of xylose/glucose isomerases.
abstract: In methanol, the reaction of stoichiometric amounts of Mn(OAc)(2)·4H(2)O and the ligand H(3)hpnbpda [H(3)hpnbpda=N,N'-bis(2-pyridylmethyl)-2-hydroxy-1,3-propanediamine-N,N'-diacetic acid] in the presence of NaOH, afforded a new water soluble dinuclear manganese(II) complex, [Mn2(hpnbpda)(μ-OAc)] (1). Similarly, the reaction of Mg(OAc)(2)·4H(2)O and the ligand H3hpnbpda in the presence of NaOH, in methanol, yielded a new water soluble dinuclear magnesium(II) complex, [Mg2(hpnbpda)(μ-OAc)(H2O)2] (2). DFT calculations have been performed for the structural optimization of complexes 1 and 2. The DFT optimized structure of complex 1 shows that two manganese(II) centers are in a distorted square pyramidal geometry, whereas the DFT optimized structure of complex 2 reveals that two magnesium(II) centers adopt a six-coordinate distorted octahedral geometry. To understand the mode of substrate binding and the mechanistic details of the active site metals in xylose/glucose isomerases (XGI), we have investigated the binding interactions of biologically important monosaccharides d-glucose and d-xylose with complexes 1 and 2, in aqueous alkaline solution by a combined approach of FTIR, UV-vis, fluorescence, and (13)C NMR spectroscopic techniques. Fluorescence spectra show the binding-induced gradual decrease in emission of complexes 1 and 2 accompanied by a significant blue shift upon increasing the concentration of sugar substrates. The binding modes of d-glucose and d-xylose with complex 2 are indicated by their characteristic coordination induced shift (CIS) values in (13)C NMR spectra for C1 and C2 carbon atoms.
authors.affiliation: Department of Chemistry, University of Kalyani, Kalyani, Nadia 741235, West Bengal, India.
authors.forename: Ayan
authors.initials: A
authors.lastname: Patra
authors.affiliation: Department of Chemistry, University of Kalyani, Kalyani, Nadia 741235, West Bengal, India. Electronic address: mbera2009@klyuniv.ac.in.
authors.forename: Manindranath
authors.initials: M
authors.lastname: Bera
mesh_terms: D019747:Aldose-Ketose Isomerases / Q000737:chemistry* / Q000378:metabolism*; D001665:Binding Sites; D002247:Carbon Isotopes; D008274:Magnesium / Q000737:chemistry* / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D008345:Manganese / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D009942:Organometallic Compounds / Q000737:chemistry* / Q000378:metabolism; D011789:Quantum Theory; D012995:Solubility; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet; D017550:Spectroscopy, Fourier Transform Infrared; D013379:Substrate Specificity; D014867:Water / Q000737:chemistry* / Q000378:metabolism
chemical_list: D002247:Carbon Isotopes; D009942:Organometallic Compounds; D014867:Water; D008345:Manganese; D019747:Aldose-Ketose Isomerases; C023298:xylose isomerase; D008274:Magnesium
keywords: Carboxylate coordination; Fluorescence spectra; Magnesium(II) complex; Manganese(II) complex; NMR spectra; Sugar binding