The determination and characterisation of 2-naphthyloxycarbonyl chloride derivatised biogenic amines in pet foods

The need to monitor biogenic amines levels is essential for many areas of the food industry for two main reasons: the caustic nature and potential toxicity of these amines, and the potential to use amine levels as markers for freshness and quality in foodstuffs. Optimised analysis conditions used for the determination of biogenic amines derivatised with 2-napthyloxycarbonyl chloride has been applied to different pet food samples to assess the effectiveness of this method for complex sample matrices. Further to this, the use of high-resolution mass spectrometry has enabled the previously unconfirmed derivatised form of seven biogenic amines to be established. The derivatised forms identified include as mono substituted (tryptamine and histamine), bisubstituted (putrescine, cadaverine and tyramine), trisubstituted (spermidine) and tetrasubstituted (spermine). The methodology of biogenic amine determination was performed successfully to a range of pet food products highlighting the applicability to a variety of complex sample matrices.     

Development and validation of a LC method for the separation and determination of the anticancer‐active FeIII(4‐methoxy‐salophene) using the new second‐generation monolith

LC method with the newly introduced second‐generation monolithic silica RP‐18e column has been developed for the separation of Fe^III(salophene) and four methoxy‐substituted Fe^III(salophene) complexes. The method has been validated for the quantitation of Fe^III(4‐OMe‐salophene), a highly active anticancer substance in vitro, bound to serum albumin. Our routinely used high‐resolution continuum‐source atomic absorption spectroscopy method based on the determination of the central iron atom was unsuitable in this case because serum originally contains significant amounts of iron as revealed by a blank sample of serum albumin. The developed LC method depends on detecting the whole complex rather than the bound iron. Two morphologically different first‐ and second‐generation HPLC monolithic columns have been compared for this purpose. The newly introduced second‐generation monolithic silica column Chromolith® HighResolution RP‐18e column (100 × 4.6 mm, Merck) separated the mixture successful within 13 min. A mobile phase consisting of 25 mM phosphate buffer pH 3/methanol (60:40, v/v) was used at a flow rate of 1 mL/min. The dynamic linear working range of the calibration curve for Fe^III(4‐OMe‐salophene) was found to be between 1 and 200 μg/mL. Detection and quantitation limits were 0.3 and 1 μg/mL, respectively.     

Mechanism of UV-induced formation of Dewar lesions in DNA

The importance of a backbone: The mechanism of formation of Dewar lesions has been investigated by using femtosecond IR spectroscopy and ab?initio calculations of the exited state. The 4π?electrocyclization is rather slow, occurs with an unusual high quantum yield, and--surprisingly--is controlled by the phosphate backbone.     

Highly Enantioselective Hetero-Diels-Alder Reaction of 1,3-Bis(silyloxy)-1,3-dienes with Aldehydes Catalyzed by Chiral Disulfonimide

Bulking up with F: The title reaction proceeds using 1?mol?% of the new perfluoroisopropyl chiral disulfonimide catalyst 1 to deliver several 2,6-disubstituted and 2,5,6-trisubstituted dihydropyrones in good yields and with excellent enantiomeric ratios. The utility of this methodology is illustrated with the first enantioselective synthesis of a potent aromatase inhibitor.     

Extremely slow Li ion dynamics in monoclinic Li(2)TiO(3)-probing macroscopic jump diffusion via(7)Li NMR stimulated echoes

A thorough understanding of ion dynamics in solids, which is a vital topic in modern materials and energy research, requires the investigation of diffusion properties on a preferably large dynamic range by complementary techniques. Here, a polycrystalline sample of Li(2)TiO(3) was used as a model substance to study Li motion by both (7)Li spin-alignment echo (SAE) nuclear magnetic resonance (NMR) and ac-conductivity measurements. Although the two methods do probe Li dynamics in quite different ways, good agreement was found so that the Li diffusion parameters, such as jump rates and the activation energy, could be precisely determined over a dynamic range of approximately eleven decades. For example, Li solid-state diffusion coefficients D(σ) deduced from impedance spectroscopy range from 10(-23) m(2) s(-1) to 10(-12) m(2) s(-1) (240-835 K). These values are in perfect agreement with the coefficients D(SAE) deduced from SAE NMR spectroscopy. As an example, D(SAE) = 2 × 10(-17) m(2) s(-1) at 433 K and the corresponding activation energy determined by NMR amounts to 0.77(2) eV (400-600 K). At room temperature D(σ) takes a value of 3 × 10(-21) m(2) s(-1).     

Two-photon fluorescence microscopy imaging of cellular oxidative stress using profluorescent nitroxides

A range of varying chromophore nitroxide free radicals and their nonradical methoxyamine analogues were synthesized and their linear photophysical properties examined. The presence of the proximate free radical masks the chromophore's usual fluorescence emission, and these species are described as profluorescent. Two nitroxides incorporating anthracene and fluorescein chromophores (compounds 7 and 19, respectively) exhibited two-photon absorption (2PA) cross sections of approximately 400 G.M. when excited at wavelengths greater than 800 nm. Both of these profluorescent nitroxides demonstrated low cytotoxicity toward Chinese hamster ovary (CHO) cells. Imaging colocalization experiments with the commercially available CellROX Deep Red oxidative stress monitor demonstrated good cellular uptake of the nitroxide probes. Sensitivity of the nitroxide probes to H(2)O(2)-induced damage was also demonstrated by both one- and two-photon fluorescence microscopy. These profluorescent nitroxide probes are potentially powerful tools for imaging oxidative stress in biological systems, and they essentially "light up" in the presence of certain species generated from oxidative stress. The high ratio of the fluorescence quantum yield between the profluorescent nitroxide species and their nonradical adducts provides the sensitivity required for measuring a range of cellular redox environments. Furthermore, their reasonable 2PA cross sections provide for the option of using two-photon fluorescence microscopy, which circumvents commonly encountered disadvantages associated with one-photon imaging such as photobleaching and poor tissue penetration.     

An expeditious synthesis of the MDM2-p53 inhibitor AM-8553

The development of the structurally complex MDM2/p53 inhibitor AM-8553 was impeded by the low yield of the initial synthesis. A second generation synthesis is described that features a Noyori dynamic kinetic resolution, a highly diastereoselective allylation, and a novel oxazoline-assisted piperidinone forming reaction to provide AM-8553 in 35.6% yield and 11 steps.     

2-(2-Methoxyphenyl)-1,3-dimethyl-1H-benzoimidazol-3-ium iodide as a new air-stable n-type dopant for vacuum-processed organic semiconductor thin films

2-(2-Methoxyphenyl)-1,3-dimethyl-1H-benzoimidazol-3-ium iodide (o-MeO-DMBI-I) was synthesized and employed as a strong n-type dopant for fullerene C(60), a well-known n-channel semiconductor. The coevaporated thin films showed a maximum conductivity of 5.5 S/cm at a doping concentration of 8.0 wt% (14 mol%), which is the highest value reported to date for molecular n-type conductors. o-MeO-DMBI-I can be stored and handled in air for extended periods without degradation and is thus promising for various organic electronic devices.     

Interchenar retrotransfer of aureothin intermediates in an iterative polyketide synthase module

The course of the enigmatic iterative use of a polyketide synthase module was deduced from targeted domain inactivation in the aureothin assembly line. Mutational analyses revealed that the N-terminus of AurA is not involved in the iteration process, ruling out an ACP-ACP shuttle. Furthermore, an AurA(KS°, ACP°)-AurA(AT(0)) heterodimer proved to be nonfunctional, whereas aureothin production was restored in a ΔaurA mutant complemented with AurA(KS°)-AurA(ACP°). This finding supports a model according to which the ACP-bound polyketide intermediate is transferred back to the KS domain on the opposite PKS strand.