Facile identification of photocleavable reactive metabolites and oxidative stress biomarkers in proteins via mass spectrometry

Described herein is a method which combines bond selective fragmentation by photodissociation with online liquid chromatographic separation and mass spectrometric analysis. Photoexcitation of proteins or peptides with 266-nm light does not normally yield abundant fragmentation; however, incorporation of a suitable carbon-sulfur or carbon-halogen bond that is proximal to a chromophore allows access to direct dissociation pathways, resulting in homolytic cleavage of these bonds. Radicals generated through this process can cause further dissociation of the peptide backbone, which is useful for site specifically identifying the point of modification. Two specific applications of this technique for peptide analysis in model systems are presented: (1) identification of reactive metabolites which covalently modify cysteine residues, and (2) characterization of halogenated tyrosine residues which are biomarkers related to oxidative stress. In both cases, these naturally occurring post translational modifications create photocleavable bonds which can be fragmented by 266-nm light. The selectivity offered by photodissociation allows facile identification of the peptides of interest even in complex mixtures, and subsequent selective radical directed backbone fragmentation pinpoints the site of modification. This combination greatly simplifies data analysis and provides more confident assignments.     

Selective determination of hydrogen peroxide by adduct formation with a dinuclear iron(III) complex and flow injection analysis/tandem mass spectrometry

A highly selective method for the determination of hydrogen peroxide is presented. In a flow injection analysis (FIA) instrument, the analyte is brought into contact with a dinuclear heptadentate iron(III) complex. The formation of the peroxide adduct is quantified using electrospray tandem mass spectrometry (ESI-MS/MS). Selected reaction monitoring (SRM) based on the transition from the triply charged peroxide adduct with m/z = 251.2 to the triply charged fragment ion of m/z = 240.5 is performed. The limit of detection for hydrogen peroxide is 10(-7) mol dm(-3), limit of quantification is 3 x 10(-7) mol dm(-3), and a linear range of 2.5 decades starting at the limit of quantification is observed.     

Effects of lipopolysaccharide-induced inflammation on expression of growth-associated genes by corticospinal neurons

Background  

Inflammation around cell bodies of primary sensory neurons and retinal ganglion cells enhances expression of neuronal growth-associated genes and stimulates axonal regeneration. We have asked if inflammation would have similar effects on corticospinal neurons, which normally show little response to spinal cord injury. Lipopolysaccharide (LPS) was applied onto the pial surface of the motor cortex of adult rats with or without concomitant injury of the corticospinal tract at C4. Inflammation around corticospinal tract cell bodies in the motor cortex was assessed by immunohistochemistry for OX42 (a microglia and macrophage marker). Expression of growth-associated genes c-jun, ATF3, SCG10 and GAP-43 was investigated by immunohistochemistry or in situ hybridisation.     

Monte-Carlo study of electromagnetic showers of high energy electrons and photons in aligned crystals

Abstract

A Monte–Carlo program to investigate electromagnetic shower formation in single crystals for particle energies up to 300 GeV is presented. It is based on the well known EGS4-code for amorphous materials and accounts for coherent radiation and pair production which arise in a crystal. Channeling radiation and crystal field assisted pair production are calculated within the uniform field approximation. The increase of energy loss of channeled electrons due to radiation cooling is also included. Good agreement with the available experimental data can be reported.     

Radiation from 39 and 45 MeV electrons channeled in Lithium Niobate

Abstract

Channeling radiation from 39 and 45 MeV electrons channeled along the <0001> axis, the (0110) plane and the (1210) plane of a 30 μm thick LiNbO ₃ crystal has been measured. Calculations of the planar crystal potentials were performed by means of the many-beam formalism. Good agreement between theory and experiment is obtained for the planar channeling radiation. Associated with channeling additional radiation lines have been observed, which may be explained by a periodic perturbation of the continuum potential.     

High-pressure cells for in situ multi-anvil experiments

A new series of high-pressure cells for in situ multi-anvil experiments is described. The cells are based on the conventional COMPRES cells, but modifications are made to improve the passage of X-rays. The modifications include cutting slits in parts of the assemblies that have very high X-ray absorption, such as lanthanum chromite and rhenium, the use of low-Z thermal insulation, such as forsterite, in place of zirconia, and the partial replacement of zirconia by MgO equatorial windows combined with a mullite octahedron. Details of the designs, thermal characterizations, and examples of the application of these cells are described.     

Beiträge zur Chemie des Phosphors. 61. Zur Struktur der Salze M(PC6H5)3, [M = K,Na]

Contributions to the Chemistry of Phosphorus. 61 About the Structure of the Salts M (PC₆H₅)₃ (M = K, Na) The structure of the salts M(PC₆H₅)₃ (M = K, Na) was determined by means of ²¹P nmr spectroscopy. Contrary to the opinion presented in the literature on the potassium salt, both compounds have an open chain structure. so that they are 1,3-Dialkali-l,2,3-triphenyl-tri-phosphides. The structure was proved by comparison of the ³¹P nnmr parameters with those of triphenyl-cyclotriphosphane 3 . and 1,2,3 triphenyl-triphosphane 5 . The occurrence of only AB₂ spin systems each for both of the pure salts as well as for an equimolecular mixture of these compounds indicates a fast inter- and possibly intramolecular metal exchange in solution. The latter of which probably takes place in the case of the solved homologue 1,-4-dipotassium-l,2,3,4-tetra-phenyl-tetraphosphide 6. for which the ³¹P nmr data indicate a quasi-cyclic conformation.