Electrospray tandem mass spectrometric analysis of zeaxanthin and its oxidation products

Carotenoids have been implicated in protection of the eye from light-mediated photo-toxicity caused by free radicals. Under conditions of normal oxidative stress the carotenoids serve as protective antioxidants; however, when the oxidative stress exceeds the antioxidant capacity, carotenoids can be oxidized into numerous cleavage products. The determination and identification of oxidized carotenoids in biological samples remains a major challenge due to the small sample size and low stability of these compounds. We investigated the reaction of various zeaxanthin cleavage products with O-ethyl hydroxylamine to evaluate their levels in a biological sample. For this, a sensitive and specific electrospray tandem mass spectrometry (ESI-MS/MS) was developed, avoiding the classical lower sensitive and specific HPLC-UV and fluorescence absorption methods. Protonated molecules [M + H](+) of carotenoids upon collision-induced dissociation produced a number of structurally characteristic product ions. A series of complicated clusters of product ions differing in 14 (CH(2))and 26 (C(2)H(2))Da was characteristic of the polyene chain of intact carotenoids. All carotenoid ethyl oximes of zeaxanthin cleavage products were characterized by the losses of 60 and 61 Da in their MS/MS spectra. Through the application of the LC/MS/MS method, we identified two oxime derivatives of 3-hydroxy-beta-ionone and 3-hydroxy-14'-apocarotenal with protonated molecules at m/z 252 and m/z 370 respectively, in a human eye sample.     

Vacuum balance and related studies of green and red rusts

Green and red rusts are formed when iron is partially or completely oxidised. Analogues of the rusts may be precipitated from iron(II) and iron (III) salt solutions treated with alkali under reducing or oxidising conditions. Variations in surface area and porosity have been investigated by gravimetric nitrogen gas sorption, using vacuum microbalance techniques.Freshly-precipitated red rusts, hydrous iron (III) oxide, have surface areas of about 200–400 m²g^?1. When they are added to iron (II) hydroxide suspensions kept at pH 7, the green Fe (II)-Fe (III) rusts formed have lower surface areas of about 40–100 m²g^?1, depending on the initial iron(II) sulphate concentrations.     

硼酸溶液中氯柱硼镁石的溶解及相转化动力学

对氯柱硼镁石（2MgO•2B2O3•MgCl2•14H2O）在4.5％H3BO3水溶液40 ℃的溶解及相转化过程进行了动力学研究.对不同时间取出的液相的化学分析及不同阶段分离固相的鉴定结果表明,该复盐在溶解阶段出现与前所报导不同的同步溶解，最终产物是库水硼镁石（2MgO•3B2O3•15H2O）.提出了库水硼镁石的形成条件和溶解及相转化动力学机理，利用单纯形优化法配合Runge-Kutta微分方程组数值解法对实验数据进行处理，给出了转化结晶动力学方程.     

液相色谱-串联质谱法同时检测饲料中多种抗氧化剂

饲料中添加抗氧化剂能够阻止或延缓饲料中某些营养物质氧化,延长饲料贮存期,从而提高饲料利用率.     

Near-infrared spectroscopy of torbernites and metatorbernites

A suite of torbernites and metatorbernites have been analysed by near-infrared spectroscopy. The spectra of torbernites and metatorbernites in the first HOH fundamental overtone are different and the spectra of torbernites of different origins in the 6000-7500 cm(-1) region vary. NIR spectroscopy provides a method of studying the hydration of cations in the interlayer of torbernite. NIR spectroscopy shows that the spectra of torbernites from different origins in the water HOH first fundamental overtone and combination regions are different. This difference implies the hydration of cations is different for torbernite minerals. The structural arrangement of the water molecules in the interlayer is sample dependent. The NIR spectra of metatorbernites are different from that of torbernites and a similarity of the spectra of metatorbernites suggests that the water structure in metatorbernites is similar.     

Studies directed toward synthesis of quassinoids. VI—mass spectral fragmentation of D-ring seco esters and δ-lactone derivatives of cholic acid

Analogy and deuterium labeling demonstrate that considerable remote group interaction occurs between functional groups at positions 7 and 16 in 16, 17-secosteroids. It is proposed that ion-dipole interact?ions separations of distances of 10 to 2 Å will involve energies of 1–30 kcal mol^?1 and can play a significant role in fragmentation processes. Successive loss of one, two and three HOAc molecules from a milecular or daughter ion increase progressively in relative intensity; irregularity in this pattern indicates the operation of special factors or multiple genesis of daughter ions having the same m/e. Evidence is presented which suggests that facile ketene ejection from the acetate functional group only occurs from a radical ion and must be preceded by transfer of a hydrogen radical from the acetate group to the site of charge localization.     

Controllable self-assembly of parallel gold nanorod clusters by DNA origami

We demonstrate the self-assembly of three types of parallel gold nanorod clusters using a rod-like DNA origami as the template.     

Microwave-prompted Rapid and Efficient Synthesis of Diacyl Thiosemicarbazides and Semicarbazides in Solvent and Catalyst Free Condition

Eighteen 1-aroyl-4-（2-iodobenzoyl）thiosemicarbazides and corresponding semicarbazides were synthesized in excellent yield under microwave irradiation in solvent and catalyst free condition.     

Substitution reactions in ionic liquids. A kinetic study

The rate of the substitution reaction of (R)-3-chloro-3,7-dimethyloctane (1) with either methanol or benzyl alcohol in mixtures containing the ionic liquid [Bmim][N(CF₃SO₂)₂] was monitored using ³⁵Cl NMR spectroscopy. The enantiomeric excess of the product, (S)-3-methoxy-3,7-dimethyloctane (2a), was analyzed using chiral gas chromatography. This product showed a decreasing enantiomeric excess with increasing concentration of ionic liquid. The rate of reaction of substrate 1 in each case varied with the concentration of the ionic liquid. Polarity measurements of the solvent mixtures were undertaken by standard methods, which are compared both to each other and to the observed rates. Solvent reorganization and selective solvation are also each proposed as contributing to the difference in the observed rates of reaction.