Negative Fast Atom Bombardment Spectra Research Articles

An Unusual Polar Lipid from the Cell Membrane of Mycoplasma fermentans

The major unidentified polar lipid (compound X), recently demonstrated in the cell membrane of Mycoplasma fermentans, was purified by preparative silicic acid column chromatography. Chemical analyses of acid-hydrolyzed compound X revealed that, in addition to fatty acids, it contains glycerol, choline and phosphate in a molar ratio of approximately 1:1:2, and an amino acid that has a retention time similar to that of homoserine. The methylated fatty acid fraction of compound X was subjected to gas-liquid chromatography and revealed methyl palmitate and methyl stearate in a 4.6:1 molar ratio. The structure of compound X was further analyzed by combining mass spectrometry, 31P-NMR and 1H-NMR. The positive and negative fast atom bombardment spectra showed a major component of M(r) 1048 and a minor component of M(r) 1076. Two different phosphate groups were identified in each of the components by 31P-NMR. Fast atom bombardment, tandem mass spectrometry, negative and positive chemical ionization mass spectrometry together with mass spectra analyses of the water-soluble and ether-soluble products obtained by methanolysis has shown that, in addition to palmitic and stearic acid residues, the presence of glycerol, ribitol, cholinephosphate and homoserinephosphate residues. It is suggested that the apparent structure of compound X is either a phosphatidylcholine attached via a phosphotriester bond to a ribitolphosphohomoserine moiety or a phosphatidylhomoserine attached via a phosphotriester bond to a ribitolphosphocholine moiety. The major molecular species is the dipalmitoylderivative (M(r) 1048), whereas the minor molecular species is a stearoyl palmitoyl derivative (M(r) 1076).

An Unusual Polar Lipid from the Cell Membrane of Mycoplasma fermentans

The major unidentified polar lipid (compound X), recently demonstrated in the cell membrane of Mycoplasma fermentans, was purified by preparative silicic acid column chromatography. Chemical analyses of acid‐hydrolyzed compound X revealed that, in addition to fatty acids, it contains glycerol, choline and phosphate in a molar ratio of approximately 1:1:2, and an amino acid that has a retention time similar to that of homoserine. The methylated fatty acid fraction of compound X was subjected to gas‐liquid chromatography and revealed methyl palmitate and methyl stearate in a 4.6:1 molar ratio. The structure of compound X was further analyzed by combining mass spectrometry, 31P‐NMR and 1H‐NMR. The positive and negative fast atom bombardment spectra showed a major component of Mr 1048 and a minor component of Mr, 1076. Two different phosphate groups were identified in each of the components by 31P‐NMR. Fast atom bombardment, tandem mass spectrometry, negative and positive chemical ionization mass spectrometry together with mass spectra analyses of the water‐soluble and ether‐soluble products obtained by methanolysis has shown that, in addition to palmitic and stearic acid residues, the presence of glycerol, ribitol, cholinephosphate and homoserinephosphate residues. It is suggested that the apparent structure of compound X is either a phosphatidylcholine attached via a phosphotriester bond to a ribitolphosphohomoserine moiety or a phosphatidylhomoserine attached via a phosphotriester bond to a ribitolphosphocholine moiety. The major molecular species is the dipalmitoylderivative (Mr 1048), whereas the minor molecular species is a stearoyl palmitoyl derivative (Mr 1076).

Mass spectrometry as an aid to the identification of ergots and dihydroergots: Comparison of hard and soft ionization techniques

An analysis of the 70 eV electron impact (EI) and fast atom bombardment (FAB) mass spectral features of a variety of ergoline and dihydroergoline derivatives of therapeutic importance is presented with emphasis upon analytical utility. Derivatives which carry non-peptide based C-8 substituents are fully characterized by EI-MS through provision of molecular weight evidence and fragment ions diagnostic of both the ergoline skeleton and the C-8 substituent. Peptidic ergolines and dihydroergolines are poorly characterized by EI-MS, but their FAB-MS clearly reveal [M + 1] + (high intensity) and [M - 1] − (high to low intensity) ions in positive and negative ion spectra, respectively. Negative FAB spectra of salts also display diagnostic anion—base conjugate ions.

Analysis of sub-microgram quantities of nucleotides by fast atom bombardment mass spectrometry.

Nucleotides of the structure P1,Pn-di(adenosine-5')-n-phosphate (n = di- through penta-) in the form of salts, and P1,P4-di(guanosine-5')tetraphosphate sodium salt have been analyzed by fast atom bombardment (FAB) mass spectrometry. A 0.2 molar solution of p-toluenesulfonic acid in glycerol has been evaluated as a matrix. In this matrix, the metal ions of the nucleotide salts are readily exchanged for protons, resulting in a simple spectrum with only one peak in the molecular ion region corresponding to the free phosphoric acid of the nucleotide plus or minus a proton (positive or negative mode), instead of the multiplicity of peaks arising from a series of metal and matrix adduct ions found with glycerol as matrix. The detection limit for analytes using this matrix is improved by a factor of ten compared to glycerol alone. It appears that the high acidity and the surfactant properties of p-toluenesulfonic acid both contribute to this result. Useful spectra are obtained from 250 ng of each of the above mentioned nucleotides, with the detection limit being somewhat lower in the positive mode. However, both positive and negative FAB spectra are useful and the results are complementary.

Fast atom bombardment mass spectrometry of nucleosides and nucleotides

The positive and negative fast atom bombardment spectra of two nucleosides, 10 mononucleotides, two derivatized mononucleotides and 11 dinucleoside monophosphates have been recorded. Molecular ions (protonated or deprotonated) and some structurally significant fragments, sometimes involving cationization, were obtained. The spectra were compared with field desorption and thermospray ionization spectra whenever possible.