Activation of methane by size-elected iron cluster cations, Fen+ (n=2-15): cluster-CHx (x=0-3) bond energies and reaction mechanisms

Journal ArticleThe kinetic energy dependences of the reactions of Fen + (n=2 - 15) with CD4 are studied in a guided ion beam tandem mass spectrometer over the energy range of 0-10 eV. All reactions exhibit thresholds and two main products, FenD+ and FenCD2+, are formed

Thermodynamics of ammonia activation by iron cluster cations: guided ion beam studies of the reactions of Fen+ (n=2-10,14) with ND3

Journal ArticleThe kinetic energy dependences of the reactions of Fen 1 (n52 - 10,14) with ND3 are studied in a guided ion beam tandem mass spectrometer over the energy range of 0-10 eV. Dehydrogenation of ammonia to form FenND1 is found to be efficient and exothermic for n54 in agreement with previous FT-ICR studies. In contrast to the ICR studies, we also observe exothermic dehydrogenation for n=3 and 5, although these processes are much less efficient than for n=4. Other clusters also undergo this process but exhibit an energy threshold

Guided ion beam studies of the reactions of Vn+ (n = 2-13) with D2: cluster-deuteride bond energies as a chemical probe of cluster electronic structure

Journal ArticleThe kinetic energy dependencies of the reactions of Vn+ (n=2 - 13) with D2 are studied in a guided ion beam tandem mass spectrometer. Products observed are VnD1 for all clusters and VnD2 + for n=4 - 13. All reactions are observed to exhibit thresholds, except for formation of VnD2 + for n =4,5,7,9,11- 13

Expression and Purification of Recombinant Von Willebrand Factor A1A2A3 Domains

In order to initiate the formation of a platelet plug Von Willebrand Factor (VWF) must be assembled into large multimers. VWF undergoes post translational modifications by dimerizing through multiple intermolecular disulfide bonds between carboxyl terminal ends of the protein and once in Golgi by forming interdimer disulfide bonds. The resulting multimers range in size between 500 to 20000 kDa. The protein dimerizes and the dimers then form a variety of disulfide crosslinked multimers with as many as 80 monomeric units, weighing more than 20 million Daltons. Studying such an enormous molecule poses special challenges. The separate domains within the VWF subunit exhibit specific properties, involving interactions with other molecules. Binding sites that are independent of multimer assembly but important for the hemostatic function are located in the A1A2A3 domains of VWF. We expressed the A1, A2, and A3 domains of von Willebrand factor in a single polypeptide using Pichia pastoris expression system. Proteins with disulfide bonds, requiring post translational modifications and glycosylation can be produced in their correctly native folded states with full function from Pichia pastoris. We purified the A1A2A3 domain using ethanol, ammonium sulfate precipitation and ion exchange chromatography. Our efforts in solubilizing the purified protein were unsuccessful more likely due to the unusual adhesive nature of the A1A2A3 domain of the VWF

Proteomic analysis of Salmonella enterica serovar Enteritidis following propionate adaptation

<p>Abstract</p> <p>Background</p> <p><it>Salmonella </it>Enteritidis is a highly prevalent and persistent foodborne pathogen and is therefore a leading cause of nontyphoidal gastrointestinal disease worldwide. A variety of stresses are endured throughout its infection cycle, including high concentrations of propionate (PA) within food processing systems and within the gut of infected hosts. Prolonged PA exposure experienced in such milieus may have a drastic effect on the proteome of <it>Salmonella </it>Enteritidis subjected to this stress.</p> <p>Results</p> <p>In this study, we used 2 D gel electrophoresis to examine the proteomes of PA adapted and unadapted <it>S</it>. Enteritidis and have identified five proteins that are upregulated in PA adapted cultures using standard peptide mass fingerprinting by MALDI-TOF-MS and sequencing by MALDI LIFT-TOF/TOF tandem mass spectrometry. Of these five, two significant stress-related proteins (Dps and CpxR) were shown (via qRT-PCR analysis) to be upregulated at the transcriptional level as well. Unlike the wild type when adapted to PA (which demonstrates significant acid resistance), PA adapted <it>S</it>. Enteritidis ∆<it>dps </it>and <it>S</it>. Enteritidis ∆<it>cpxR </it>were at a clear disadvantage when challenged to a highly acidic environment. However, we found the acid resistance to be fully restorable after genetic complementation.</p> <p>Conclusions</p> <p>This work reveals a significant difference in the proteomes of PA adapted and unadapted <it>S</it>. Enteritidis and affirms the contribution of Dps and CpxR in PA induced acid resistance.</p

Perturbations in the electronic spectrum of HCl and DCl.

Perturbations in the electronic spectrum of HCl and DCl

Proteomic Changes in the Plasma of Broiler Chickens with Femoral Head Necrosis

Femoral head necrosis (FHN) is a skeletal problem in broiler chickens, where the proximal femoral head cartilage shows susceptibility to separation from its growth plate. The selected birds with FHN showed higher body weights and reduced plasma cholesterol. The proteomic differences in the plasma of healthy and FHN-affected chickens were explored using matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF-MS) and liquid chromatography/electrospray ionization-tandem mass spectrometry (LC-MS/MS) to prospect for protein biomarkers. We isolated two differentially expressed low molecular weight proteins and identified them by MALDI peptide mass fingerprinting as fibrinogen- and fetuinderived peptides, respectively. These peptides were reduced in birds susceptible to femoral head problems. Quantitation of LC-MS/MS spectra showed elevated levels of gallinacin-9, apolipoprotein A1, and hemoglobin and reduced levels of alpha-1-acid glycoprotein, albumin, and SPINK7 proteins in FHN. These results suggest that the bodyweight and the lipid profiles along with the above proteins can be useful as noninvasive biomarkers of FHN