Structural characterization of toxic cyclic peptides from blue-green algae by tandem mass spectrometry.

Combined use of chemical degradation, derivatization, and tandem mass spectrometry for rapid structural characterization of toxic cyclic peptides from blue-green algae at the nanomole level is described. Previously, all blue-green algal toxins were thought to belong to a family of seven-residue cyclic peptides, having the general structure cyclo-D-Ala-L-Xaa-erythro-beta-methyl-D-isoaspartic acid-L-Yaa-Adda-D-isoglutamic acid-N-methyldehydroalanine, where Xaa and Yaa represent variable amino acids of the L configuration and Adda is 3-amino-9-methoxy-2,6,8-trimethyl-10-phenyl-deca-4,6-dienoic acid. Structural characterization of two additional toxins indicates that further variability can exist within this family of naturally occurring toxic cyclic peptides. Isoaspartic acid and dehydroalanine can substitute for beta-methylisoaspartic acid and N-methyldehydroalanine, respectively.

A hybrid HRGC/MS/MS method for the characterization of tetrachlorinated-p-dioxins in environmental samples.

A new instrumental method for the characterization of the analyte 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) by selected reaction monitoring (SRM) analysis is investigated. The method uses high-resolution gas chromatography coupled to a hybrid tandem mass spectrometer. The technique was evaluated with regard to four performance parameters: sensitivity, linearity, repeatability and selectivity. The method compares favorably with the traditional selected ion monitoring HRGC/HRMS technique, and the selectivity of the new method is shown to surpass the established HRGC/HRMS method. This new method could allow the characterization of samples that have undergone less rigorous cleanup than is now possible by the traditional mass spectrometric methods. The presence of TCDDs in a real sample was confirmed by using the new HRGC/(hybrid)MS/MS SRM method, which was not possible by using HRGC/HRMS analysis.

Structure and biological relationships of Coxiella burnetii lipopolysaccharides.

Lipopolysaccharides (LPSs) extracted from nine strains of Coxiella burnetii were analyzed for chemical compositions, molecular heterogeneity by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and lethal toxicities in galactosamine-sensitized mice. The structure of a unique disaccharide of hydrolyzed phase I LPS was determined to be galactosaminuronyl-alpha (1-6)-glucosamine (GalNU-alpha (1-6)-GlcN, C12H22N2O10) with an Mr of 354. The Mr of LPSs of C. burnetii intra- and interspecific strains and the content of GalNU-alpha (1-6)-GlcN and two sugars, virenose and dihydrohydroxystreptose, were used as biochemical markers of truncated LPSs. Smooth-phase I LPS contained all three compounds, semi-rough-phase I LPS did not contain virenose, and rough-phase II LPS contained none of the three compounds. These analyses indicate that the intermediate to larger Mr LPSs require the addition of GalNU-alpha (1-6)-GlcN and dihydrohydroxystreptose to obtain the major (10.5 kDa), the intermediate (between 10.5 and 27 kDa), and the minor (23 kDa) LPS bands. The addition of virenose to the major and the minor bands produced the large Mr phase I LPSs. Extreme microheterogeneity in the banding profile ranging in Mr from the 2.5 to 10.5 kDa may be due to unidentified components, while the microheterogeneity in Mr of the 10.5-kDa and larger LPS bands is related to variations in the compounds described here. All of the LPSs were toxic in galactosamine-sensitized mice, albeit they were 100-1000-fold less toxic than Escherichia coli and Salmonella typhimurium endotoxin.

Metabolic profiles of penaied shrimp: dietary lipids and ovarian maturation.

The major impediment to the culture of penaeid shrimp in captivity in the United States has been an inability to obtain ovarian maturation and spawning. Lipid profiles of tissues (gonads, hepatopancreas, and tail muscle) of Penaeus setiferus caught at sea have shown that cholesterol is the dominant sterol and that polyunsaturated fatty acids known to be essential in man comprise a significant portion of the fatty acid fraction. A prioprietary marine ration contains cholesterol, but is devoid of polyunsaturated fatty acids. Ovarian maturation and spawning were obtained when the shrimp diet was supplemented with an annelid rich in lipids containing these compounds. The biochemical significance of these findings is discussed.