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M D LeBlanc

Publications and source records attributed to M D LeBlanc.

3 recordsLinked to original sources
PubMed2000

An annotated catalog of inverted repeats of Caenorhabditis elegans chromosomes III and X, with observations concerning odd/even biases and conserved motifs.

We have taken a computational approach to the problem of discovering and deciphering the grammar and syntax of gene regulation in eukaryotes. A logical first step is to produce an annotated catalog of all regulatory sites in a given genome. Likely candidates for such sites are direct and indirect repeats, including three subcategories of indirect repeats: inverted (palindromic), everted, and mirror-image repeats. To that end we have produced a searchable database of inverted repeats of chromosomes III and X of Caenorhabditis elegans, the first completely sequenced multicellular eukaryote. Initial results from the use of this catalog are observations concerning odd/even biases in perfect IRs. The potential usefulness of the catalog as a discovery tool for promoters was shown for some of the genes involved with G-protein functions and for heat shock protein 104 (hsp104).

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PubMed1992

Determination of erythromycin A in salmon tissue by liquid chromatography with ion-spray mass spectrometry.

A reverse-phase liquid chromatography/mass spectrometry (LC/MS) method, incorporating gradient elution, is described for the characterization of residual erythromycin A and its metabolites in salmon tissue. The method uses ion-spray, a mild atmospheric pressure ionization technique which provides an abundant protonated molecule well suited for selected ion monitoring experiments. Tandem mass spectrometry (MS/MS) using collision-induced dissociation was used to provide structural information. The LC/MS method was tested for the analysis of salmon tissue spiked with erythromycin A at levels between 0.01 and 1 p.p.m. A simple extraction and clean-up procedure, slightly modified from that described by Takatsuki et al. (J. Assoc. Off. Anal. Chem. 70, 708 (1987)), was used in this work. Using selected ion and selected reaction monitoring techniques, the LC/MS and LC/MS/MS methods provided detection limits of < 10 and 50 ng g-1, respectively. Confirmatory full-scan LC/MS and LC/MS/MS spectra were obtained at the 0.5 and 1 microgram g-1 levels, respectively. Using a combination of these techniques, the presence of residual erythromycin A was confirmed in the tissue of fish administered medicated feed containing the antibiotic. In addition, several metabolites and degradation products of erythromycin A, including anhydro-erythromycin and N-demethyl-erythromycin, were detected and where possible confirmed by comparison with authentic compounds. Although this analytical method has been shown to afford the necessary sensitivity and precision, application of these techniques to high-throughput quantitative analyses will require development of an improved clean-up procedure and preferably also of a suitable surrogate internal standard.

Animals↗