Dissociative recombination of the acetaldehyde cation, CH(3)CHO(+)

Proteomic insights on the metabolism in inflammatory bowel disease

Inflammatory bowel diseases (IBD) are chronic and relapsing inflammatory conditions of the gut that include Crohn's disease and ulcerative colitis. The pathogenesis of IBD is not completely unraveled, IBD are multi-factorial diseases with reported alterations in the gut microbiota, activation of different immune cell types, changes in the vascular endothelium, and alterations in the tight junctions’ structure of the colonic epithelial cells. Proteomics represents a useful tool to enhance our biological understanding and to discover biomarkers in blood and intestinal specimens. It is expected to provide reproducible and quantitative data that can support clinical assessments and help clinicians in the diagnosis and treatment of IBD. Sometimes a differential diagnosis of Crohn's disease and ulcerative colitis and the prediction of treatment response can be deducted by finding meaningful biomarkers. Although some non-invasive biomarkers have been described, none can be considered as the “gold standard” for IBD diagnosis, disease activity and therapy outcome. For these reason new studies have proposed an “IBD signature”, which consists in a panel of biomarkers used to assess IBD. The above described approach characterizes “omics” and in this review we will focus on proteomics.

Variable temperature rate studies for the reaction H3O(+) + (C2H2)2 measured with a coaxial molecular beam radio frequency ring electrode ion trap

The independent molecule and ion temperature dependence of the rate coefficient for the H(3)O(+) and (C(2)H(2))(2) reaction producing C(2)H(5)O(+) are determined using a coaxial molecular beam radio frequency ring electrode ion trap (CoMB-RET). The H(3)O(+) temperature is varied from 25 to 170 K, while the equilibrated C(2)H(2)/(C(2)H(2))(2) beam temperatures sampled are 160, 180, 200, and 220 K. The rate coefficient of the H(3)O(+) + (C(2)H(2))(2) reaction is determined to be 4.0 × 10(-10) × (T(react)/300)(-2.5) in the reaction temperature range of T(react) = 114-187 K. The H(3)O(+) and C(2)H(2) radiative association reaction is found to have a rate coefficient below 1 × 10(-13) cm(3)·s(-1) at 187 K. This result is consistent with Herbst's experimental determination.

Fourier transform infrared matrix-isolation analysis of acetaldehyde fragmentation products after charge exchange with Ar•+ under varied ionization density conditions

The products of the Ar(•+) charge exchange ionization of acetaldehyde have been isolated and compared with related photoionization results and computational work. Acetaldehyde has been used to assess the effect of varied ion density in the ionization region of the electron bombardment matrix isolation apparatus. The amount of acetaldehyde destruction has been measured for constant gas-sample composition and constant ionization current for two anode geometries: a pin anode and a plate anode. For the same ionization current, a pin-shaped anode demonstrates higher precursor molecule destruction efficiency (85%) than the plate-shaped anode (30%), resulting in substantial effect on the yield and quantity of isolated products. When the plate anode is used, the observed infrared products correspond to matrix-isolated carbon monoxide (CO), methane (CH(4)), ketene (CH(2)CO), ethynyloxy radical (HCCO), formyl radical (HCO(•)), acetyl radical (CH(3)CO(•)), vinyl alcohol (H(2)C = CH-OH), and cationic proton-bound dimer, Ar(2)H(+). When the pin anode is used, the same products are observed with different relative proportions and new absorption features corresponding to dicarbon monoxide (CCO) and methyl radical (CH(3)(•)) are observed. The surprising observation of infrared absorptions corresponding to vinyl alcohol along with low yield of products anticipated through the analysis of photoelectron-photoionization coincidence measurements suggests that the initially formed fragmentation products are able to further react within the matrix-isolation environment to influence observed product yields. Related experiments, using the isotopomer CD(3)CHO, suggest that the observed products are formed via radical-radical reactions that occur under the high pressure conditions of the matrix isolation environment.