Dissolved urate salts out calcium oxalate in undiluted human urine in vitro: implications for calcium oxalate stone genesis

Hyperuricosuria has long been documented as a predisposing factor to calcium oxalate (CaOx) stone pathogenesis. However, its mechanism is still without sound scientific foundation. Previously, we showed that hyperuricosuria, simulated by the addition of dissolved sodium urate, promotes the crystallization of CaOx. In the present study, we demonstrate that the urate's effect on the crystallization is attributable to its salting out CaOx from solution. Furthermore, analysis of urines revealed that their metastable limit decreased with increases in the product of the prevailing concentrations of calcium and urate: this has implications for CaOx stone genesis. We also outline anti-salting out strategies for future research for the prevention and/or treatment of CaOx calculi.     

Multispectral and hyperspectral image analysis of elemental and micro-Raman maps of cross-sections from a 16th century painting

Spectroscopic imaging is well suited to the study of micro-samples from artworks, where the sample material is limited and the maximum amount of information needs to be obtained. In this study, a new approach to imaging elemental data from energy dispersive X-ray analysis maps was used in conjunction with micro-Raman spectroscopic imaging to characterise the paint layers within micro-samples. Cross-sections from the 16th century painting Portrait of a Youth were found to contain vermilion, lead-tin yellow type 1 and a blue-green pigment consistent with terre-verte. The mid-preparatory layer (imprimatura) contains a high proportion of elements and mineral inclusions that indicates a clay-type composition. The ground layer was identified as anhydrite with large gypsum inclusions. The pigments and composition of the preparatory layers are consistent with those used by Italian Renaissance artist Dosso Dossi.     

ESI‐MS/MS of expanded porphyrins: a look into their structure and aromaticity

Electrospray mass spectrometry/mass spectrometry was used to investigate the gas‐phase properties of protonated expanded porphyrins, in order to correlate those with their structure and conformation. We have selected five expanded meso‐pentafluorophenyl porphyrins, respectively, a pair of oxidized/reduced fused pentaphyrins (22 and 24 π electrons), a pair of oxidized/reduced regular hexaphyrins (26 and 28 π electrons) and a regular doubly N‐fused hexaphyrin (28 π electrons). The gas‐phase behavior of the protonated species of oxidized and reduced expanded porphyrins is different. The oxidized species (aromatic Hückel systems) fragment more extensively, mainly by the loss of two HF molecules. The reduced species (Möbius aromatic or Möbius‐like aromatic systems) fragment less than their oxidized counterparts because of their increased flexibility. The protonated regular doubly fused hexaphyrin (non‐aromatic Hückel system) shows the least fragmentation even at higher collision energies. In general, cyclization through losses of HF molecules decreases from the aromatic Hückel systems to Möbius aromatic or Möbius‐like aromatic systems to non‐aromatic Hückel systems and is related to an increase in conformational distortion. Copyright © 2016 John Wiley & Sons, Ltd.     

Electrooxidation of nitrite on a silica-cerium mixed oxide carbon paste electrode

A silica-cerium mixed oxide (SiCe) was prepared by the sol-gel process, using tetraethylorthosilicate and cerium nitrate as precursors and obtained as an amorphous solid possessing a specific surface area of 459 m(2) g(-1). Infrared spectroscopy of the SiCe material showed the formation of the Si-O-Ce linkage in the mixed oxide. Scanning electron microscopy/energy dispersive spectroscopy indicated that the cerium oxide particles were homogenously dispersed on the matrix surface. X-ray diffraction and (29)Si solid-state nuclear magnetic resonance implied non-crystalline silica matrices with chemical environments that are typical for silica-based mixed oxides. X-ray photoelectron spectroscopy showed that Ce was present in approximately equal amounts of both the 3+ and 4+ oxidation states. Cyclic voltammetry data of electrode prepared from the silica-cerium mixed oxide showed a peak for oxidation of Ce(3+)/Ce(4+) at 0.76 V and electrochemical impedance spectroscopy equivalent circuit indicated a porous structure with low charge transfer resistance. In the presence of nitrite, the SiCe electrode shows an anodic oxidation peak at 0.76 V with a linear response as the concentration of the analyte increases from 3×10(-5) at 3.9×10(-3) mol L(-1).