Synthetic preparation and immunological evaluation of ß-mannosylceramide and related N-acyl analogues.

The synthesis of the invariant natural killer (iNK) T cell agonist ß-mannosylceramide along with a series of fatty amide analogues is reported. Of the six ß-glycosylation protocols investigated, the sulfoxide methodology developed by Crich and co-workers proved to be the most effective where the reaction of a mannosyl sulfoxide and phytosphingosine derivative gave a key glycolipid intermediate as a 95 : 5 mixture of ß- to α-anomers in high yield. A series of mannosyl ceramides were evaluated for their ability to activate D32.D3 NKT cells and induce antitumour activity.

Real-time differentiation of ethylbenzene and the xylenes using selected ion flow tube mass spectrometry.

RATIONALE: Monitoring of isomeric analytes using mass spectrometry usually requires a time-consuming chromatographic separation of the analytes before analysis. Selected ion flow tube mass spectrometry (SIFT-MS) can provide rapid direct analysis of ethylbenzene and xylene by utilizing the different reaction chemistry of the isomers. O2 + yields the same product ions from each isomer but in different ratios. OH- yields different product ions. METHODS: The reaction chemistry of C8 H10 with the reagent ion OH- generated from a microwave discharge of moist air in a commercial SIFT-MS instrument was utilized in this study. The product ion from OH- yielded ions at different masses for each isomer. To gain an understanding of how the product ion from ethylbenzene of HO2 - was generated, a theoretical study of the potential reaction surface was undertaken that accounted for the experimental observations. RESULTS: Measurements of OH- with ethylbenzene showed the product ion to be HO2 - at m/z 33. The reaction of OH- with xylene yielded the major product ion at m/z 105, C8 H9 - . HO2 - also underwent a slow secondary reaction with CO2 and O2 present from air in the samples. These findings were supported by calculations of the potential energy surface for the reactions. Measurements made on a certified gas mixture of ethylbenzene and xylene in the concentration range up to 5000 ppbv gave a linear response for each analyte. CONCLUSIONS: A fast, efficient method was developed for monitoring xylene and ethylbenzene in a mixture without the need for chromatographic separation before analysis using SIFT-MS.