Variability in urinary oxalate measurements between six international laboratories

Hyperoxaluria is a major risk factor for kidney stone formation. Although urinary oxalate measurement is part of all basic stone risk assessment, there is no standardized method for this measurement.

Correlation between Accurate Electron Density and Linear Optical Properties in Amino Acid Derivatives: L-Histidinium Hydrogen Oxalate

The accurate electron density and linear optical properties of L-histidinium hydrogen oxalate are discussed. Two high-resolution single crystal X-ray diffraction experiments were performed and compared with density functional calculations in the solid state as well as in the gas phase. The crystal packing and the hydrogen bond network are accurately investigated using topological analysis based on quantum theory of atoms in molecules, Hirshfeld surface analysis, and electrostatic potential mapping. The refractive indices are computed from couple perturbed Kohn-Sham calculations and measured experimentally. Moreover, distributed atomic polarizabilities are used to analyze the origin of the linear susceptibility in the crystal, in order to separate molecular and intermolecular causes. The optical properties are also correlated with the electron density distribution. This compound also offers the possibility to test the electron density building block approach for material science and different refinement schemes for accurate positions and displacement parameters of hydrogen atoms, in the absence of neutron diffraction data.

Chiral Templating Activity of Tris(bipyridine)ruthenium(II) Cation in the Design of Three-Dimensional (3D) Optically Active Oxalate-Bridged {[Ru(bpy) 3 ][Cu 2 x Ni 2(1 - x ) (C 2 O 4 ) 3 ]} n (0 ≤ x ≤ 1; bpy = 2,2‘-bipyridine): Structural, Optical, and Magnetic Studies

Three-dimensional oxalate-based {[Ru(bpy)3][Cu2xNi2(1-x)(ox)3]}n (0≤ x ≤ 1, ox = C2O42-, bpy = 2,2‘bipyridine) were synthesized. The structure was determined for x = 1 by X-ray diffraction on single crystal. The compound crystallizes in the cubic space group P4132. It shows a three-dimensional 10-gon 3-connected (10,3) anionic network where copper(II) has an unusual tris(bischelated) environment. X-ray powder diffraction patterns and their Rietveld refinement show that all the compounds along the series are isostructural and single-phased. According to X-ray absorption spectroscopy, copper(II) and nickel(II) have an octahedral environment, respectively elongated and trigonally distorted. As shown by natural circular dichroism, the optically active forms of {[Ru(bpy)3][CuxNi2(1-x)(ox)3]}n are obtained starting from resolved Δ- or Λ-[Ru(bpy)3]2+. The Curie−Weiss temperatures range between −55 (x = 1) and −150 K (x = 0). The antiferromagnetic exchange interaction thus decreases when the copper contents increases in agreement with the crystallographic structure of the compounds and the electronic structure of the metal ions. At low temperature, the compounds exhibit complex long-range ordered magnetic behavior.

Polyfunctional Two- (2D) and Three- (3D) Dimensional Oxalate Bridged Bimetallic Magnets

We report major results concerning polyfunctional two- (2D) and three- (3D) dimensional oxalate bridged bimetallic magnets. As a consequence of their specific organisation they are composed of an anionic sub-lattice and a cationic counter-part. These bimetallic polymers can accommodate various counter-cations possessing specific physical properties in addition to the magnetic ones resulting from the interactions between the metallic ions in the anionic sub-lattice. Thus, molecular magnets possessing paramagnetic, conductive and optical properties are presented in this review.

Molecular-Based Magnetism in Bimetallic Two-Dimensional Oxalate-Bridged Networks. An X-ray and Neutron Diffraction Study

Bimetallic, oxalate-bridged compounds with bi- and trivalent transition metals comprise a class of layered materials which express a large variety in their molecular-based magnetic behavior. Because of this, the availability of the corresponding single-crystal structural data is essential to the successful interpretation of the experimental magnetic results. We report in this paper the crystal structure and magnetic properties of the ferromagnetic compound {[N(n-C3H7)4][MnIICrIII(C2O4)3]}n (1), the crystal structure of the antiferromagnetic compound {[N(n-C4H9)4][MnIIFeIII(C2O4)3]}n (2), and the results of a neutron diffraction study of a polycrystalline sample of the ferromagnetic compound {[P(C6D5)4][MnIICrIII(C2O4)3]}n (3). Crystal data:  1, rhombohedral, R3c, a = 9.363(3) Å, c = 49.207(27) Å, Z = 6; 2, hexagonal, P63, a = 9.482(2) Å, c = 17.827(8) Å, Z = 2. The structures consist of anionic, two-dimensional, honeycomb networks formed by the oxalate-bridged metal ions, interleaved by the templating cations. Single-crystal field dependent magnetization measurements as well as elastic neutron scattering experiments on the manganese(II)−chromium(III) samples show the existence of long-range ferromagnetic ordering behavior below Tc = 6 K. The magnetic structure corresponds to an alignment of the spins perpendicular to the network layers. In contrast, the manganese(II)−iron(III) compound expresses a two-dimensional antiferromagnetic ordering.

Crystal Structures, Magnetic Structures and Photophysics in Supramolecular Transition-Metal Oxalate Compounds

Polymeric two- and three-dimensional, homo- and heterometallic oxalatebridged coordination compounds offer exciting opportunities, mainly in the fields of molecular magnetism and photophysics. Given that a large variety of magnetic phenomena have been reported so far from these molecular magnets, very limited experience is gained from elastic neutron scattering experiments. Therefore, with two examples, we will address the topic of the elucidation of magnetic structures by means of the neutron scattering technique. In addition, due to the possibility of the variation of different metal ions in varying oxidation states, interesting photophysical processes can be observed within the extended three-dimensional host/guest systems.

Chiral, Three-Dimensional Supramolecular Compounds: Homo- and Bimetallic Oxalate- and 1,2-Dithiooxalate-Bridged Networks. A Structural and Photophysical Study.

In analogy to the [M(II)(bpy)(3)](2+) cations, where M(II) is a divalent transition-metal and bpy is 2,2'-bipyridine, the tris-chelated [M(III)(bpy)(3)](3+) cations, where M(III) is Cr(III) or Co(III), induce the crystallization of chiral, anionic three-dimensional (3D) coordination polymers of oxalate-bridged (&mgr;-ox) metal complexes with stoichiometries [M(II)(2)(ox)(3)](n)()(2)(n)()(-) or [M(I)M(III)(ox)(3)](n)()(2)(n)()(-). The tripositive charge is partially compensated by inclusion of additional complex anions like ClO(4)(-), BF(4)(-), or PF(6)(-) which are encapsulated in cubic shaped cavities formed by the bipyridine ligands of the cations. Thus, an elaborate structure of cationic and anionic species within a polymeric anionic network is realized. The compounds isolated and structurally characterized include [Cr(III)(bpy)(3)][ClO(4)] [NaCr(III)(ox)(3)] (1), [Cr(III)(bpy)(3)][ClO(4)][Mn(II)(2)(ox)(3)] (2), [Cr(III)(bpy)(3)][BF(4)] [Mn(II)(2)(ox)(3)] (3), [Co(III)(bpy)(3)][PF(6)][NaCr(III)(ox)(3)] (4). Crystal data: 1, cubic, P2(1)3, a = 15.523(4) Å, Z = 4; 2, cubic, P4(1)32, a = 15.564(3) Å, Z = 4; 3, cubic, P4(1)32, a = 15.553(3) Å, Z = 4; 4, cubic, P2(1)3, a = 15.515(3) Å, Z = 4. Furthermore, it seemed likely that 1,2-dithiooxalate (dto) could act as an alternative to the oxalate bridging ligand, and as a result the compound [Ni(II)(phen)(3)][NaCo(III)(dto)(3)].C(3)H(6)O (5) has successfully been isolated and structurally characterized. Crystal data: 5, orthorhombic, P2(1)2(1)2(1), a = 16.238(4) Å, b = 16.225(4) Å, c = 18.371(5) Å, Z = 4. In addition, the photophysical properties of compound 1 have been investigated in detail. In single crystal absorption spectra of [Cr(III)(bpy)(3)][ClO(4)][NaCr(III)(ox)(3)] (1), the spin-flip transitions of both the [Cr(bpy)(3)](3+) and the [Cr(ox)(3)](3)(-) chromophores are observed and can be clearly distinguished. Irradiating into the spin-allowed (4)A(2) --> (4)T(2) absorption band of [Cr(ox)(3)](3)(-) results in intense luminescence from the (2)E state of [Cr(bpy)(3)](3+) as a result of rapid energy transfer processes.

Orientation dependent molecular friction on organic layer compound crystals

High resolution friction force maps of the benzylammonium terminated crystalline surface of a layer compound are presented. The lateral force map acquired with an atomic force microscope, reveals a significant contrast between different molecular orientations yielding molecular rows which differ from their neighboring ones. The single crystals are formed by stacks of copper oxalate sheets sandwiched between stereoregular organic cations, resulting in highly organized surface structures. Single molecular defects are observed at small loads. The experimental results are compared with numerical calculations which indicate a transition from an unperturbed state at small loads to a distorted state at higher loads. (C) 2011 American Institute of Physics.

Pathophysiology and diagnosis of nephrocalcinosis

Nephrocalcinosis is the result of a myriad of hereditary or acquired diseases in the calcium, phosphate or oxalate metabolism that lead to deposition of calcium containing precipitates within the kidney. Nephrocalcinosis and nephrolithiasis are pathophysiologically tightly related and often co-exist. In the case of recurrent nephrolithiasis, nephrocalcinosis has to be excluded. Stone analysis can yield important clues to the underlying disease process. The best way to diagnose nephrocalcinosis and an accompanying nephrolithiasis is by native computer tomography scans. Untreated, nephrocalcinosis will lead to a progressive decline in renal function and eventually to end stage renal disease. Thus, for each case, the underlying disease process has to be determined and a causative therapy initiated.

Isolated extraordinary daytime urinary frequency of childhood: a case series of 26 children in Switzerland

BACKGROUND: The term 'isolated extraordinary daytime urinary frequency' designates an abnormally increased diurnal frequency of painless urination in a completely toilet-trained child with normal urinalysis. METHODS: We report the history of 26 children (16 boys and 10 girls; aged between 4.1 and 10 years) who were referred to us between 2002 and 2006 and subsequently diagnosed with this condition. RESULTS: Possible psychosocial problems, or recent emotional stressors, were disclosed in the majority of the children: recent (36 months or less) asylum seekers (n = 9), school-related problems (n = 4), parental divorce (n = 2) or death of the mother (n = 1). Possible dietary causes were observed in 9 patients: oxalate-rich beverages (n = 5) and liberal ingestion of 'acidic' juices (n = 4). A diet low in oxalates was recommended when children were consuming large quantities of oxalate-rich beverages; and a diet low in acidic juice was recommended in those liberally ingesting acidic juices. Reassurance and observation were the approach in the remaining cases. The median duration of the symptoms was 5 months. A longer (p < 0.05) duration was noted in children of asylum seekers. CONCLUSIONS: This functional condition is easily identifiable, but often under- or misdiagnosed. Confounding the condition might result in redundant investigation.