A glycoside flavonoid in kudzu (Pueraria lobata)

Kudzu (Pueraria lobata) foliage has been touted as a possible energy crop. High-performance liquid chromatography and mass spectrometry analysis of the methanolic kudzu foliage extracts confirmed the presence of robinin (kaempferol-3-O-robinoside-7-O-rhamnoside). Robinin accounted for 0.65±0.16% (dry basis) of kudzu biomass. Fast performance liquid chromatography (FPLC) was employed to fractionate robinin from the crude extract. The antioxidant capacity of robinin was evaluated by an oxygen radical absorbance capacity (ORAC) assay. The ORAC values of pure standard were compared with those of the extract fractions. One milligram of the FPLC-fractionated robinin generated an ORAC value of 5.15±2.00 μmol/mg of Trolox, whereas 1 mg of pure robinin generated an ORAC value of 12.34±0.45 μmol/mg of Trolox. Because of its antioxidant properties, robinin may be a flavonoid worth extracting prior to energy production.     

Identification of Hypoxic Cells Using an Organotellurium Tag Compatible with Mass Cytometry

Mass cytometry (MC) offers unparalleled potential for the development of highly parameterized assays for characterization of single cells within heterogeneous populations. Current reagents compatible with MC analysis employ antibody‐metal‐chelating polymer conjugates to report on the presence of biomarkers. Here, we expand the utility of MC by developing the first activity‐based probe designed specifically for use with the technology. A compact MC‐detectable telluroether is linked to a bioreductively sensitive 2‐nitroimidazole scaffold, thereby generating a probe sensitive to cellular hypoxia. The probe exhibits low toxicity and is able to selectively label O₂‐deprived cells. A proof‐of‐concept experiment employing metal‐bound DNA intercalators demonstrates that a heterogeneous mixture of cells with differential exposure to O₂ can be effectively discriminated by the quantity of tellurium‐labeling. The organotellurium reagents described herein provide a general approach to the development of a large toolkit of MC‐compatible probes for activity‐based profiling of single cells.     

Electrocrystallization of cadmium on anodically formed titanium oxide

The electrocrystallization of Cd on previously anodized Ti substrates was studied by means of electrochemical techniques and SEM images in three different solutions of CdSO₄ (2, 10, and 50 mM). Voltammetric characterization showed the typical behavior of metal electrodeposition on conducting substrates, and potentials for electrodeposition of Cd were identified. However, the response obtained at different potentials in current transients exhibited an abnormal behavior suggesting the influence of TiO₂ on the process of electrocrystallization. The characterization of the obtained electrodeposits by SEM images allowed relating electrochemical with morphological changes, in particular, variations in the crystal size and shape as well as formation of presumably Cd branches on the substrate surface. This behavior only allowed the analysis of current transients of the electrodeposits obtained in 2 mM CdSO₄ solution using general equation for diffusion-controlled 3D growth and relating parameters of Cd crystal growth on anodized Ti electrode with the observed morphological changes.     

Determination of glucan phosphorylation using heteronuclear 1H,13C double and 1H,13C,31P triple‐resonance NMR spectra

Phosphorylation and dephosphorylation of starch and glycogen are important for their physicochemical properties and also their physiological functions. It is therefore desirable to reliably determine the phosphorylation sites. Heteronuclear multidimensional NMR‐spectroscopy is in principle a straightforward analytical approach even for complex carbohydrate molecules. With heterogeneous samples from natural sources, however, the task becomes more difficult because a full assignment of the resonances of the carbohydrates is impossible to obtain. Here, we show that the combination of heteronuclear ¹H,¹³C and ¹H,¹³C,³¹P techniques and information derived from spectra of a set of reference compounds can lead to an unambiguous determination of the phosphorylation sites even in heterogeneous samples. Copyright © 2013 John Wiley & Sons, Ltd.     

Transmission of Molecular Structure on NMR Characteristics of Phosphorus-Nitrogen Double Bond Systems

Abstract

Elucidation of the origin for the large variability of 31P and I5N chemical shifts in compounds with P-N double bonds is a challenging task. We demonstrate here how trends in 3lP and 15N chemical shifts of iminophosphines and ylene-iminophosphoranes can be explained by the use of quantum chemical model concepts.     

Simultaneous Determination of Antimony(III) and Molybdenum(VI) by Adsorptive Stripping Voltammetry Using Quercetin as Complexing Agent

A sensitive and selective voltammetric method for simultaneous determination of Sb(III) and Mo(VI) using Quercetin (Q) as complexing agent is described. Optimal conditions were found to be: pH 3.7, C_Q=6.0 µmol L^?1 and E_acc=?0.10 V. The LOD (3σ) for Sb(III) are 0.076 and 0.040 µg L^?1, whereas for Mo(VI) are 0.086 and 0.048 µg L^?1 with t_acc of 60 and 120 s, respectively. The method was validated using synthetic sea water (ASTM D665) and was applied to the determination of Sb(III) and Mo(VI) in natural waters with satisfactory results.