The analysis of haloethylenes using Resonance Electron Capture - Mass Spectrometry and data analysis software

Resonance Electron Capture Mass Spectrometry (REC-MS) is a sensitive experimental technique for the study of gas-phase compounds with positive electron affinity. This technique was used to study a class of compounds known as baloetbylenes containing chlorine and bromine substitutions. Haloetbylenes are an important class of compounds because ethylene is the simplest model system for studying resonance electron capture for larger π bond networks and the effects of substitution, both in position and type. Secondly, haloethylenes are environmental contaminants that result from large-scale industrial use thereby making it important to study methods that can produce additional specificity in environmental analysis and assist in unambiguously identifing the specific compound(s) present. Through experimentation a correlation was found showing that increasing chlorine substitution resulted in a lowering of the effective yield maximum for Cl⁻ in chioroethylenes and that these chioroethylenes can be identified by the shape and maxima of the yield curves. Additional fragmentation channels not previously observed were recorded and molecular ions (Mt) were observed for tetrachioroethylene and trichioroethylene, which were not previously known to exist. Higher energy fragmentations (6-10 eV) most likely result from Feshbach resonances involving the neutral (N) electronic to singlet (S) state transition. The effective yield maximum at 8 eV for production of the C₂Cl⁻ from tetrachioroethylene represents a special case and may result from a Feshbaeh resonance at the ionization potential of the parent molecule. Bromoethylenes have effective yield maxima that result from lower energy electron attachment for comparable fragmentation channels for chioroethylene species. A total of seven channels not having a maximum near zero eV were observed in bromoethylenes. No molecular ions were observed in any of the bromoethylenes studied. Theoretical studies show that the vertical electron attachment energy of a compound is dependent upon the type, number, and location of substituents while the adiabatic electron affinity is dependent upon the type and number of substituents but not on the regiochemistry. Additional theoretical work has led to a new explanation for Cl⁻ fragment ions that occur with electrons of near to zero eV energy from tetrachioroethylene as possibly arising through a predissociation mechanism that allows for π* and σ* mixing in a non-coplanar structure of the negative ion. Additional work was done to improve data analysis by developing a Visual Basic (VB) based software to parse data in output flIes. The program was entitled "Extractor" and resulted in a dramatic savings in time for data processing

Speeding up TOMAWAC by means of improved numerical methods

Hydrodynamic

Regulation of intracellular free arachidonic acid in Aplysia nervous system

We have studied the regulation of arachidonic acid (AA) uptake, metabolism, and release in Aplysia nervous system. Following uptake of [ 3 H]AA, the distribution of radioactivity in intracellular and extracellular lipid pools was measured as a function of time in the presence or absence of exogenous AA. The greatest amount of AA was esterified into phosphatidylinositol (relative to pool size). We found that the intracellular free AA pool underwent rapid turnover, and that radioactive free AA and eicosanoids were released at a rapid rate into the extracellular medium, both in the presence and absence of exogenous AA. Most of the released radioactivity originated from phosphatidylinositol.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/48020/1/232_2005_Article_BF01868464.pd

Electron molecule interactions of amino acids and peptides

Electron-biomolecule interactions are a biologically relevant field of study because there are several ion fragmentation techniques that have come to the forefront in mass spectrometric analysis that involve the interaction of charged peptides and free electrons. By studying the electron energies that cause fragmentation in neutral amino acids, amino acid derivatives, and peptides, new insights into the mechanisms of biomolecule damage and ion fragmentation have been gained. Low energy electron capture experiments performed on a standard mass spectrometer using a specifically designed probe for non-volatile compounds provided proof of principle for low energy electron capture leading to peptide fragments. The largest assigned ion from a peptide was the z7-1 ion from the peptide substance P. For peptides with carboxylic acids on the C-terminus, z-1 ions were observed along with (M-H)- ions for peptides smaller than a hexamer. The assignment of the ions produced by low energy electron capture to c and z-1 ions was supported by high resolution low electron energy negative ion mass spectrometry with the alanine dimer. Using resonance electron capture – mass spectrometry, the amino acid esters, i.e. ethyl, isopropyl, and t-butyl esters of glycine, alanine, and phenylalanine were studied and these showed effective yield peaks at 3.5-3.7 eV and 8.8–9.5 eV for the carboxylate negative ions that were not observed for the underivatized amino acids or their methyl esters. The effective yield peaks in the carboxylate negative ions are attributed to electronically excited Feshbach resonances. N-Acetyl amino acids and peptides show strong ions with effective yield maxima at 1-2 eV electron energy that are due to shape resonances of the π* orbital. The dominant ions are either the (M-H)- or z-1 ions for the compounds with cterminal carboxylic acids. Their methyl esters show c ions as the dominant fragments. The cleavage of the peptide backbone involves π* - σ* orbital mixing because capture occurs by the π orbitals but sigma bonds are ultimately cleaved. The general conclusion of this thesis is that electrons with energy between 1-2 eV are captured by shape resonances of the π* orbital at the amide bond leading to formation of z-1 and c type ions

Effect of a swim training on homocysteine and cysteine levels in rats.

International audienceThe purpose of this study was to investigate the effects of a 8-week of swim training on total plasma homocysteine and cysteine levels in 16 male Sprague-Dawley rats aged 17 weeks. We also evaluated the activity of hepatic cystathionine beta-synthase (CBS), an enzyme involved in the metabolism of Hcy, the concentration of plasma glutathione, taurine, and a fraction of vitamin B6: the pyridoxal 5-phosphate (PLP). After one week of acclimatization, rats were randomly divided into two groups: 8 non-trained (NTR) and 8 trained rats (TR). Following the training period, body weight gain was lower in TR than in NTR. Plasma homocysteine did not differ among groups while significantly lower plasma cysteine and taurine levels were found in TR (157.83 +/- 8.6 micromol/L; 133.01 +/- 9.32 micromol/L; P < 0.05) compared with data of NTR (176.19 +/- 4.9 micromol/L; 162.57 +/- 8.16 micromol/L; P < 0.05). No significant changes in hepatic CBS activity were observed in TR compared with NTR. Moreover, values for plasma glutathione and PLP concentrations were not affected by training.These results indicate that training reduces plasma cysteine and taurine levels whereas it does not modify other studied parameters. Thus, physical training may regulate cysteine metabolism

Fragmentation of peptide negative molecular ions induced by resonance electron capture

A simple robust method to study resonance gas-phase reactions between neutral peptides of low volatility and free electrons has been designed and implemented. Resonance electron capture (REC) experiments were performed by several neutral model peptides and two naturally occurring peptides. The assignment of negative ions (NIs) formed in these gas-phase reactions was based on high mass-resolving power experiments. From these accurate mass measurements, it was concluded that fragment NIs formed by low (1–2 eV) energy REC are of the same types as those observed in electron capture∕transfer dissociation, where the positive charge is a factor. The main feature resulting from these REC experiments by peptides is the occurrence of zn−1 ions, which are invariably of the highest abundances in the negative ion mass spectra of larger peptides. [M–H]− NIs presumably the carboxylate anion structure dominate the REC spectra of smaller peptides. There was no evidence for the occurrence of the complementary reaction, i.e., the formations of cn+1 ions. Instead, cn ions arose without hydrogen∕proton transfer albeit with lower abundances than that observed for zn−1 ions. Only the amide forms of small peptides showed more abundant ion peaks for the cn ions than for the zn−1 ions. The mechanisms for the N–Cα bond cleavage are discussed

On your feet: protocol for a randomized controlled trial to compare the effects of pole walking and regular walking on physical and psychosocial health in older adults

Physical activity is associated with better physical and mental health in older adults. Pole walking is a form of walking which may have additional health benefits in older adults, because of the addition of hand held poles, and consequent upper limb involvement. However, few studies have examined the potential additional effects of pole walking on physical and psychosocial health in older adults compared with walking. The aim of this study is to compare the effect of a pole walking program with the effects of a walking program, on physical and psychosocial wellbeing, in older adults in assisted living facilitie