A Prismatic Analyser concept for Neutron Spectrometers

A development in modern neutron spectroscopy is to avoid the need of large samples. We demonstrate how small samples together with the right choice of analyser and detector components makes distance collimation an important concept in crystal analyser spectrometers. We further show that this opens new possibilities where neutrons with different energies are reflected by the same analyser but counted in different detectors, thus improving both energy resolution and total count rate compared to conventional spectrometers. The technique can be combined with advanced focusing geometries and with multiplexing instrument designs. We present a combination of simulations and data with 3 energies from one analyser. The data was taken on a prototype installed at PSI, Switzerland, and shows excellent agreement with the predictions. Typical improvements will be 2 times finer resolution and a factor 1.9 in flux gain compared to a Rowland geometry or 3 times finer resolution and a factor 3.2 in flux gain compared to a single flat analyser slab

Mitochondrial proteomics on human fibroblasts for identification of metabolic imbalance and cellular stress

<p>Abstract</p> <p>Background</p> <p>Mitochondrial proteins are central to various metabolic activities and are key regulators of apoptosis. Disturbance of mitochondrial proteins is therefore often associated with disease. Large scale protein data are required to capture the mitochondrial protein levels and mass spectrometry based proteomics is suitable for generating such data. To study the relative quantities of mitochondrial proteins in cells from cultivated human skin fibroblasts we applied a proteomic method based on nanoLC-MS/MS analysis of iTRAQ-labeled peptides.</p> <p>Results</p> <p>When fibroblast cultures were exposed to mild metabolic stress – by cultivation in galactose medium- the amount of mitochondria appeared to be maintained whereas the levels of individual proteins were altered. Proteins of respiratory chain complex I and IV were increased together with NAD⁺-dependent isocitrate dehydrogenase of the citric acid cycle illustrating cellular strategies to cope with altered energy metabolism. Furthermore, quantitative protein data, with a median standard error below 6%, were obtained for the following mitochondrial pathways: fatty acid oxidation, citric acid cycle, respiratory chain, antioxidant systems, amino acid metabolism, mitochondrial translation, protein quality control, mitochondrial morphology and apoptosis.</p> <p>Conclusion</p> <p>The robust analytical platform in combination with a well-defined compendium of mitochondrial proteins allowed quantification of single proteins as well as mapping of entire pathways. This enabled characterization of the interplay between metabolism and stress response in human cells exposed to mild stress.</p

Oligopeptide Sequences of the Metal Binding Domain of CueR Metalloregulatory Proteins as Candidates for Toxic Metal Ion Capture

Various toxic metal ion resistance systems operate from bacterial level up to higher plants and animals. In bacteria, metalloregulatory proteins are key factors in the control of metal ion level. Inspired by the metal binding domain of these highly sensitive metal ion sensor proteins we have designed artificial oligopeptides, containing two cysteine residues, and investigated their interaction with cadmium(II) and mercury(II) ions. The studied ligands bound both metal ions with a rather high stability. The composition and solution structure of the various metal ion complexes have been determined. The genetic code of one of the oligopeptide sequences has been introduced into E. coli BL21 cells and (over)produced in the form of a fusion protein. Preliminary investigation of the viability and potential metal ion accumulation of the modified bacteria, compared to control cells, in the presence of cadmium(II) and mercury(II) has also been performed