A negative ion electrospray ionization tandem mass spectrometric technique was developed for the analysis of glycerophospholipids. Examination of the product ion mass spectrum of the deprotonated molecular ion provided sufficient information to identify both the class of glycerophospholipid and the molecular weights of the two fatty acid moieties. This technique was applied to the profiling of glycerophospholipids present in the chloroform/methanol extracts of four different bacterial species. The principal bacterial phospholipids detected by this technique were phosphatidylglycerols and diphosphatidylglycerols, accompanied by small amounts of phosphatidylethanolamines for two of the bacterial species examined. The fatty acid composition of the phosphatidylglycerols for each bacteria was determined by tandem mass spectrometry and presented graphically. Differences in the fatty acid composition for each bacterial species were readily apparent from a visual examination of the data sets.

Muramic acid is an amino sugar found in eubacterial cell walls and not elsewhere in nature. This study explored the use of electrospray tandem mass spectrometry (ESI MS/MS) in analysis of underivatized muramic acid in bacterial hydrolysates. Fungal hydrolysates were used as negative controls. The only processing used was hydrolysis in sulfuric acid followed by extraction with an organic base (N,N-dioctylmethylamine) to remove the acid prior to ESI MS/MS analysis. Compared with pure muramic acid, bacterial hydrolysates produced more complex ESI mass spectra, such that the protonated molecular ion at m/z 252 was barely detectable. In contrast, product ion spectra of m/z 252 were identical among pure muramic acid, Gram positive bacteria, and Gram negative bacteria. However, no characteristic product ion spectrum was manifested from m/z 252 in fungal samples. This allowed ready, visual differentiation of bacteria and fungi. Multiple reaction monitoring (MRM) following muramic acid fragmentations (m/z 252-->144 and m/z 252-->126) increased sensitivity and allowed quantitative differentiation when compared with the MRM of the internal standard N-methyl-D-glucamine (m/z 196-->44). ESI MS/MS required minimal sample preparation and allowed rapid sample throughput for analysis of muramic acid in whole bacterial cell hydrolysates.

Curie-point wire and quartz tube pyrolysis (Py) devices coupled to short column (2 and 5 meter) gas chromatography/mass spectrometry (GC/MS) systems are investigated for their ability to extract microbiologically-useful information from unprocessed, underivatized whole microorganisms. The U.S. Department of the Army is sponsoring the development of a Chemical, Biological Mass Spectrometer (CBMS) system to autonomously operate in fielded situations. As such, data are presented that are relevant to the design of a fieldable device such as the CBMS system. Ubiquitous (e.g. nucleic acid bases) as well as more highly specific (e.g. certain lipids) biological constituents are addressed for their use in microorganism detection and characterization by Py-GC/MS. The need for rapid generation of useful information is presented as well as the desire for a simplified graphical representation suitable for direct interpretation as opposed to purely computerized "black box" pattern recognition methods.

Cluster size distribution and collision-induced dissociation (CID) studies of protonated methanol and protonated methanol-water clusters yield information on the structure and energetics of such ions. Ions were formed at atmospheric pressure in a corona discharge source, and were subjected to CID in the center quadrupole of a triple quadrupole mass spectrometer. Cluster ions containing up to 13 molecules of methanol and/or water were observed and examined using CID experiments. The CID of all (CH3OH)n . H2O . H+ clusters, where n less-than-or-equal-to 8, showed that water loss was statistically favored over methanol loss and that the preferred dissociation channel involved loss of water with methanol molecules. These results support a model employing a chain of hydrogen-bonded solvent molecules rather than one in which fused rings of ligands surround a central hydronium ion. However, CID of larger clusters, where n greater-than-or-equal-to 9, showed that loss of one methanol was equal to or less than loss of water, reflecting a change in structure.