A spectrophotometric assay for nitrate in an excess of nitrite.

Miranda et al. have developed a method for simultaneous evaluation of nitrate and nitrite concentrations using reduction of nitrate by vanadium(III) combined with detection by the acidic Griess reaction [K.M. Miranda, M.G. Espey, D.A. Wink, A rapid, simple spectrophotometric method for simultaneous detection of nitrate and nitrite, Nitric Oxide 5 (2001) 62-71]. The sensitivity of the nitrate assay decline if the mixture analyzed contains a large excess of nitrite relative to nitrate, for instance, in the case of oxidation products of nitric oxide (NO) in aerated solutions, or in sweat. By this reason nitrite should be removed before the nitrate assay, if [NO2-]>[NO3-]. Here we lay out an improved method allowing the above limitation to be erased, using sulfamic acid for nitrite removal. We also describe some modifications that enhance the reproducibility of the assay.     

Thiamine deficiency caused by thiamine antagonists triggers upregulation of apoptosis inducing factor gene expression and leads to caspase 3-mediated apoptosis in neuronally differentiated rat PC-12 cells

Recent evidence suggests that alterations in oxidative metabolism induced by thiamine deficiency lead to neuronal cell death. However, the molecular mechanisms underlying this process are still under extensive investigation. Here, we report that rat pheochromocytoma PC-12 cells differentiated in the presence of NGF into neurons undergo apoptosis due to thiamine deficiency caused by antagonists of thiamine - amprolium, pyrithiamine and oxythiamine. Confocal laser scanning fluorescence microscopy revealed that annexin V binds to PC-12 cells in presence of thiamine antagonists after 72 h incubation. Results also show that thiamine antagonists trigger upregulation of gene expression of mitochondrial-derived apoptosis inducing factor, DNA fragmentation, cleavage of caspase 3 and translocation of active product to the nucleus. We therefore propose that apoptosis induced by amprolium, pyrithiamine or oxythiamine occurs via the mitochondria-dependent caspase 3-mediated signaling pathway. In addition, our data indicate that pyrithiamine and oxythiamine are more potent inducers of apoptosis than amprolium.     

A micro-fluidic study of whole blood behaviour on PMMA topographical nanostructures

Background  

Polymers are attractive materials for both biomedical engineering and cardiovascular applications. Although nano-topography has been found to influence cell behaviour, no established method exists to understand and evaluate the effects of nano-topography on polymer-blood interaction.     

Synthesis of a natural product-inspired eight-membered ring lactam library via ring-closing metathesis

We have prepared a novel speculative eight-membered lactam demonstration library based on the skeletal structure of the potent antitumor marine natural product octalactin A. The basic scaffold was readily constructed in a convergent fashion via ring-closing metathesis chemistry from the corresponding diene amides. A cursory examination of the biological properties of the library validates the relevance and significance of these structures.     

A SPOT on the chromatin landscape? Histone peptide arrays as a tool for epigenetic research

Post-translational modifications of histones serve as docking sites and signals for effector proteins and chromatin-remodeling enzymes, thereby influencing many fundamental cellular processes. Nevertheless, there are huge gaps in the knowledge of which proteins read and write the 'histone code'. Several techniques have been used to decipher complex histone-modification patterns. However, none is entirely satisfactory owing to the inherent limitations of in vitro studies of histones, such as deficits in the knowledge of the proteins involved, and the associated difficulties in the consistent and quantitative generation of histone marks. An alternative technique that could prove to be a useful tool in the study of the histone code is the use of synthetic peptide arrays (SPOT blot analysis) as a screening approach to characterize macromolecules that interact with specific covalent modifications of histone tails.