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Biomedical subjects

R B Cody

Publications and source records attributed to R B Cody.

7 recordsLinked to original sources
PubMed2000

Electron monochromator mass spectrometry for the analysis of whole bacteria and bacterial spores.

Spores from a variety of Bacillus species were analyzed with direct probe mass spectrometry using an electron monochromator to select electrons of distinct energies for ionization. Electron energies were chosen to match the electron capture energies of taxonomically important compounds such as dipicolinic acid and fatty acids. Previous negative ion interferences were not observed when the monochromator was used, and the signal-to-noise ratio of targeted compounds was significantly enhanced using this approach. To demonstrate the selectivity of the technique, the monochromator was swept over a range of electron energies while monitoring the masses of compounds with known electron capture energies. Scanning the monochromator while the mass spectrometer was operated in single-ion mode enabled dipicolinic acid to be detected in 10(5) spores. The results presented here demonstrate the utility of the electron monochromator for selectively ionizing compounds directly in bacteria and bacterial spores.

Bacillus↗
PubMed2000

High-resolution LC/MS for analysis of minor components in complex mixtures: negative ion ESI for identification of impurities and degradation products of a novel oligosaccharide antibiotic.

High-resolution mass spectrometry has been routinely used for structural confirmation and identification; however, it has mostly been applied to relatively pure samples. Exact mass measurement of minor components such as impurities, degradation products or metabolites in complex mixtures has been difficult without prior separation and isolation. Here we report the utilization of on-line liquid chromatography in combination with high-resolution mass spectrometry for the identification of impurities and base degradation products of Sch 27899, a member of the everninomicin class of antibiotics. Nine Sch 27899-related impurities and degradation products were detected by negative ion electrospray ionization using a magnetic sector mass spectrometer. Exact mass measurements were obtained at a resolution of 5000 using polyethylene glycol (PEG) sulfates as internal standards. Corresponding elemental compositions were determined within a 2 ppm error tolerance and structures were proposed for all components.

Aminoglycosides↗
PubMed1995

A structural assignment for a stable acetaldehyde-lysine adduct.

Acetaldehyde is the first oxidation product of ethanol in vivo. Lysine residues in proteins such as hemoglobin have been implicated as target structures for acetaldehyde adducts resulting from ethanol consumption. Although the presence of both stable and unstable acetaldehyde-hemoglobin adducts has been established, the structural characterization of the adducts has received relatively little attention. As a model for such adduct formation, we studied the peptide pentalysine in vitro. Pentalysine has several potential sites for adduct formation. The amino-terminal amine group as well as the epsilon-amine groups of each lysine side chain can serve as potential sites for modification by acetaldehyde. Mass spectrometry, nuclear magnetic resonance, and Raman spectroscopy were employed to demonstrate that acetaldehyde forms a stable linkage to lysine amine groups via a Schiff base.

Acetaldehyde↗
PubMed1990

Hadamard transform measurement of tandem Fourier-transform mass spectra.

The simultaneous collection of multiple spectra using tandem (MS/MS) and multidimensional (MS/MS/MS) mass spectrometry from multiple precursors is demonstrated to yield correspondingly enhanced sensitivity. This approach utilizes Hadamard transform deconvolution and takes advantage of the multichannel dissociation capability of Fourier-transform mass spectrometry. By application of this to an 11-component mixture, the 11 spectra of the products of dissociating 11 different combinations of six of the component molecular ions are measured; Hadamard transformation yields individual spectra of the precursor ions exhibiting a signal-to-noise improvement of 1.8x over spectra measured separately, as predicted by theory. Precursor ion selection with high specificity and product formation with high abundance reproducibility are critical; spurious peaks resulting from imperfect reproducibility can be minimized by using simultaneous equation coefficients reflecting the degree of precursor dissociation. Extension of this technique to MSn spectra is demonstrated with simultaneous MS/MS/MS monitoring of three precursors and three daughters yielding nine spectra representing the nine possible dissociation pathways. For MSn spectra, coding the product relationships for each additional step (e.g., precursor----daughter, daughter----granddaughter) requires elimination of half of the remaining ions. No ions are lost for coding in an improved Hadamard approach in which the combined daughter spectrum of the selected half of the precursors is subtracted from that of the other half.

Fourier Analysis↗
PubMed1985

Analgesic potencies of morphine 3- and 6-sulfates after intracerebroventricular administration in mice: relationship to structural characteristics defined by mass spectrometry and nuclear magnetic resonance.

Morphine 3-sulfate, which carries a polar, acidic group at the 3-position much like morphine, does not differ greatly in analgesic potency from morphine following intracerebroventricular administration. This differs from the non-ionizable 3-methyl and 3-ethyl ethers, which are less potent analgesics than morphine. Morphine 6-sulfate, which differs from morphine by having an ionizable group at carbon-6 at physiological pH, is a more potent analgesic than morphine following intracerebroventricular administration. Variations in analgesic potency following modifications at the hydroxyl groups appear only to reflect alterations in point charges rather than structural alterations.

Analgesics↗
PubMed1985

Peptide mixture sequencing by tandem Fourier-transform mass spectrometry.

Picomole samples of the linear peptide gramicidin D and cyclic peptide gramicidin S are shown to be impure by the laser-desorption formation of multiple groups of molecular adduct peaks by using Fourier-transform mass spectrometry. Selective excitation of the molecular peaks of the major sample component followed by collisionally activated dissociation provides complete sequence information for the cyclic decapeptide and for 12 of the 15 amino acids of the linear peptide. This instrumentation shows striking advantages in sensitivity, resolution, and mass accuracy in comparison to tandem mass spectrometers used previously.

Amino Acid Sequence↗