Enhancement of atmospheric pressure chemical ionization for the determination of free and glycine-conjugated bile acids in human serum

A highly sensitive and accurate method based on the precolumn derivatization of bile acids (BA) with a high ionization efficiency labeling reagent 1,2-benzo-3,4-dihydrocarbazole-9-ethyl-benzenesulfonate (BDEBS) coupled with LC/MS has been developed. After derivatization, BA molecules introduced a weak basic nitrogen atom into the molecular core structure that was readily ionized in commonly used acidic HPLC mobile phases. Derivatives were sufficiently stable to be efficiently analyzed by atmospheric pressure chemical ionization (APCI)-MS/MS in positive-ion mode. The MS/MS spectra of BA derivatives showed an intense protonated molecular ion at m/z [M + H](+). The collision-induced dissociation of the molecular ion produced fragment ions at [MH - H2O](+), [MH - 2H(2)O](+), [MH - 3H(2)O](+). The characteristic fragment ions were at m/z 320.8, 262.8, and 243.7 corresponding to a cleavage of N - CO, O - CO, and C - OCC, respectively, and bonds of derivatized molecules. The selected reaction monitoring, based on the m/z [M + H]+ -> [MH - H2O](+), [MH - H2O](+), [MH - 2H(2)O](+), [MH-3H(2)O](+), 320.8, 262.8, and 243.7 transitions, was highly specific for the BA derivatives. The LODs for APCI in a positive-ion mode, at an S/N of 5, were 44.36-153.6 fmol. The validation results showed high accuracy in the range of 93-107% and the mean interday precision for all standards was < 15% at broad linear dynamic ranges (0.0244-25nmol/mL). Good linear responses were observed with coefficients of > 0.9935 in APCI/MS detection. Therefore, the facile BDEBS derivatization coupled with mass spectrometric analysis allowed the development of a highly sensitive and specific method for the quantitation of trace levels of the free and glycine-conjugated BA from human serum samples.

Influence of several non-nutrient additives on nonspecific immunity and growth of juvenile turbot, Scophthalmus maximus L.

The effects of three non-nutrient additives on nonspecific immunity and growth of juvenile turbot (Scophthalmus maximus L.) were studied in this feeding experiment. The five treatments are basal diet alone, basal diets containing three different additives [0.4 g kg(-1) of xylo-oligosaccharides (XOS), 1.3 g kg (-1) of yeast cell wall and 0.8 g kg (-1) of bile acids] individually or in combination. Two hundred and twenty-five turbots (average initial weight 151.3 +/- 11.3 g) were randomly allotted in five treatments with three replicates within each treatment in a 72-day period. Comparing with basal diet group, activities of C3, C4, phagocyte, lysozyme, specific growth rate and feed conversion rate in yeast cell wall, XOS and the combined groups was enhanced significantly (P < 0.05); however, these parameters in bile acid groups were increased slightly (P > 0.05) except for phagocyte (P < 0.05); superoxide dismutase activity in additive groups was not significantly increased (P > 0.05) except for the combined group (P < 0.05). In conclusion, supplementation of yeast cell wall and XOS enhanced the nonspecific immunity of juvenile turbot. Synergistic or additive effect of the three additives was not observed.

Secondary structural analysis of the mRNA regions encoding the hemagglutinin cleavage site basic amino acids of the avian influenza virus H5N1 subtype samples

Here we report the codon bias and the mRNA secondary structural features of the hemagglutinin (HA) cleavage site basic amino acid regions of avian influenza virus H5N1 subtypes. We have developed a dynamic extended folding strategy to predict RNA secondar