Human C4A peptide

Aspirin-exacerbated respiratory disease (AERD) has attracted a great deal of attention because of its association with increased asthma severity. To identify plasma biomarkers for the prediction of AERD, the six most abundant plasma proteins (albumin, IgG, antitrypsin, IgA, transferrin, and haptoglobin) in pooled plasma samples were removed using a multiple affinity removal system column. Two-dimensional gel electrophoresis (2DE) was used for differential display proteomic analysis of the pooled plasma. Proteins were identified by matrix assisted laser desorption ionization time-of-flight (MALDI-TOF)/TOF. Enzyme-linked immunosorbent assay (ELISA) was performed to identify and quantify apolipoprotein H (Apo H) in plasma from subjects with AERD and aspirin-tolerant asthma (ATA). Eight protein spots showed differences in relative intensity between pooled plasma from subjects with AERD (n = 8) and those with ATA (n = 8). MALDI-TOF/TOF analysis showed decreases in the levels of alpha-fibrinogen precursor, Apo H, fibrin beta, and proapolipoprotein in AERD as compared with ATA, and increases in chain A human complement component C3, 90-kDa heat shock protein, complement component C4a, and kininogen-1 isoform 2. Apo H concentrations were significantly increased in plasma from subjects with ATA than those with AERD and normal controls, as measured by ELISA (P < 0.01). AERD is characterized by changes in the levels of proteins involved in the coagulation and complement pathways. In addition, Apo H is up-regulated in ATA compared to AERD and normal controls, suggesting that Apo H may be involved in different pathogenesis of ATA from AERD. (C) 2013 Published by Elsevier Ltd.

The 2,6-di-tert-butyl-4-methoxyphenoxyl radical is shown to dimerize in solution and in the solid state. The X-ray crystal structure of the dimer, the first for a para-coupled phenoxyl radical, revealed a bond length of 1.6055(23) angstrom for the C4-C4a bond. This is significantly longer than typical C-C bonds. Solution equilibrium studies using both optical and IR spectroscopies showed that the kg for dissociation is 1.3 +/- 0.2 M at 20 degrees C, indicating a C-C bond dissociation free energy of -0.15 +/- 0.1 kcal mol(-1). Van't Hoff analysis gave an exceptionally small bond dissociation enthalpy (BDE) of 6.1 +/- 0.5 kcal mol(-1). To our knowledge, this is the smallest BDE measured for a C-C bond. This very weak bond shows a large deviation from the correlation of C-C bond lengths and strengths, but the computed force constant follows Badger's rule.