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Liquid Secondary Ion Mass Spectrometry (liquid + secondary_ion_mass_spectrometry)
Selected AbstractsInvestigation of ion-pair precipitates of selected alkoxylates and complex salts of specific metal cations by liquid secondary ion mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 4 2002Abstract Liquid secondary ion (LSI) mass spectra of ion-pair precipitates obtained for Triton X-100 with strontium, lead, cadmium and mercury tetraphenylborates and for selected butoxylene,ethoxylene monoalkyl ethers with barium tetraiodobismuthate(III) are discussed. On the basis of LSI mass spectra, recorded in both positive and negative modes, the formulae of the ion-pair precipitates were determined. On the basis of B/E mass spectra, the fragmentation routes of [M , H + Ba]+ ions for butoxylene,ethoxylene monoalkyl ether complexes of barium and [M , H + Cd]+ ions for the Triton X-100 complex of cadmium are proposed. Copyright © 2002 John Wiley & Sons, Ltd. [source] Formation of cryptophanes from their precursors as viewed by liquid secondary ion mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 10 2001Thierry Brotin Abstract The formation of cryptophane-A (C1) and the deuterated cryptophanes C2,C6 from their respective precursors P1,P6 in a mass spectrometer ion-source was evidenced by liquid secondary ion mass spectrometry (LSIMS). Mass-analyzed ion kinetic energy experiments performed on the precursor molecular ions suggested that cryptophane formation occurred mainly in the liquid-matrix before desorption rather than in the gas phase. In addition, we observed that the presence of cations, such as lithium or sodium ions, inhibited the formation of the cryptophane molecular ions. In the light of these results we used the LSIMS technique to investigate the formation of the new cryptophanes C7,C13. All the data collected support the idea that a direct comparison can be made between these experimental findings and chemistry in solution. Copyright © 2001 John Wiley & Sons, Ltd. [source] Mass spectrometric and chemical stability of the Asp-Pro bond in herpes simplex virus epitope peptides compared with X-Pro bonds of related sequencesJOURNAL OF PEPTIDE SCIENCE, Issue 8 2002Zsolt Skribanek Abstract The mass spectrometric analysis of the immunodominant epitope region (273,284) of herpes simplex virus type 1 (HSV-1) glycoprotein D (gD) showed a favoured fission at the Asp-Pro peptide bond. The fast atom bombardment collision induced dissociation (FAB-CID) study of closely related X-Pro peptides documented that neither the length nor the amino acid composition of the peptide has a significant influence on this preferential cleavage. At the same time the DP bond proved to be sensitive to acidic conditions in the course of peptide synthesis. These observations prompted us to compare the chemical and mass spectrometric stability of a new set of nonapeptides related to the 273,284 epitope region of gD, i.e. SALLEDPVG and SALLEXPVG peptides, where X = A, K, I, S, F, E or D, respectively. The chemical stability of these peptides during acidic hydrolysis was investigated by electrospray ionization mass spectrometry (ESI-MS) and the products were identified by ESI-MS and on-line high performance liquid chromatography,mass spectrometry (HPLC-MS). The mass spectrometric fragmentation and bond stability of the untreated peptide samples were also studied using ESI-MS and liquid secondary ion mass spectrometry (LSIMS). Both the chemical hydrolysis and the mass spectrometric fragmentation showed that the Asp-Pro bond could easily be cleaved, while the KP bond proved to be stable under both circumstances. On the other hand, the XP bond (X = A, I, S, F or E) fragmented easily under the mass spectrometric conditions, but was not sensitive to the acidolysis. Copyright © 2002 European Peptide Society and John Wiley & Sons, Ltd. [source] ,Bubble chamber model' of fast atom bombardment induced processesRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 15 2003Marina V. Kosevich A hypothesis concerning FAB mechanisms, referred to as a ,bubble chamber FAB model', is proposed. This model can provide an answer to the long-standing question as to how fragile biomolecules and weakly bound clusters can survive under high-energy particle impact on liquids. The basis of this model is a simple estimation of saturated vapour pressure over the surface of liquids, which shows that all liquids ever tested by fast atom bombardment (FAB) and liquid secondary ion mass spectrometry (SIMS) were in the superheated state under the experimental conditions applied. The result of the interaction of the energetic particles with superheated liquids is known to be qualitatively different from that with equilibrium liquids. It consists of initiation of local boiling, i.e., in formation of vapour bubbles along the track of the energetic particle. This phenomenon has been extensively studied in the framework of nuclear physics and provides the basis for construction of the well-known bubble chamber detectors. The possibility of occurrence of similar processes under FAB of superheated liquids substantiates a conceptual model of emission of secondary ions suggested by Vestal in 1983, which assumes formation of bubbles beneath the liquid surface, followed by their bursting accompanied by release of microdroplets and clusters as a necessary intermediate step for the creation of molecular ions. The main distinctive feature of the bubble chamber FAB model, proposed here, is that the bubbles are formed not in the space and time-restricted impact-excited zone, but in the nearby liquid as a ,normal' boiling event, which implies that the temperature both within the bubble and in the droplets emerging on its burst is practically the same as that of the bulk liquid sample. This concept can resolve the paradox of survival of intact biomolecules under FAB, since the part of the sample participating in the liquid,gas transition via the bubble mechanism has an ambient temperature which is not destructive for biomolecules. Another important feature of the model is that the timescale of bubble growth is no longer limited by the relaxation time of the excited zone (,10,12,s), but rather resembles the timescale characteristic of common boiling, sufficient for multiple interactions of gas molecules and formation of clusters. Further, when the bubbles burst, microdroplets are released, which implies that FAB processes are similar to those in spraying techniques. Thus, two processes contribute to the ion production, namely, release of volatile solvent clusters from bubbles and of non-volatile solute from sputtered droplets. This view reconciles contradictory views on the dominance of either gas-phase or liquid-phase effects in FAB. Some other effects, such as suppression of all other ions by surface-active compounds, are consistent with the suggested model. Copyright © 2003 John Wiley & Sons, Ltd. [source] Mechanistic investigation of the interaction between bisquaternary antimicrobial agents and phospholipids by liquid secondary ion mass spectrometry and differential scanning calorimetryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 18 2002V. A. Pashynskaya Mechanisms of interaction between the antimicrobial drugs decamethoxinum and aethonium, which are based on bisquaternary ammonium compounds, and a phospholipid component of biological membranes, dipalmitoylphosphatidylcholine, were studied by means of liquid secondary ion mass spectrometry (LSIMS) and differential scanning calorimetry (DSC). Supramolecular complexes of the drugs with this phospholipid were recorded under secondary ion mass spectrometric conditions. The dependence of the structures of these complexes on structural parameters of the dications of the bisquaternary ammonium compounds was demonstrated. Tandem mass spectrometric investigations of the metastable decay of doubly charged ions of decamethoxinum and aethonium complexes with dipalmitoylphosphatidylcholine allowed estimation of structural parameters of these complexes in the gas phase. Interactions of decamethoxinum and aethonium with model membrane assemblies built from hydrated dipalmitoylphosphatidylcholine were studied using DSC. It was shown that while both drugs can interact with model membranes, the mechanisms of such interactions for decamethoxinum and aethonium differ. The correlation between the nature of these interactions and structural and electronic parameters of the dications of the two bisquaternary agents is discussed. Interpretation of combined mass spectrometric and calorimetric experimental data led to proposals that the molecular mechanisms of antimicrobial action of bisquaternary ammonium compounds are related to their effect on the membrane phospholipid components of microbial cells. Copyright © 2002 John Wiley & Sons, Ltd. [source] Identification of hemes and related cyclic tetrapyrroles by matrix-assisted laser desorption/ionization and liquid secondary ion mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 12 2002Hyung-Sun Youn Mass spectrometry has proven to be a powerful technique applicable on trace amounts for the identification of known hemes and cyclic tetrapyrroles, and for providing critical information for the structure of new and novel versions. This report describes investigations of the practical limits of detection for such bioinorganic prosthetic groups, primarily by liquid secondary ion mass spectrometry (LSIMS) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS), including a survey of the utility of common matrices. The lower limit of detection under favorable conditions extends to low picomole amounts. Certain derivatization techniques, such as methyl esterification and chelation to zinc, both increase the sensitivity of analyses and provide spectroscopic signatures that enable heme/cyclic tetrapyrrole ions to be identified in the presence of contaminants. Copyright © 2002 John Wiley & Sons, Ltd. [source] | ||||||||||