Gary L. Glish

Mass spectrometry/mass spectrometry : techniques and applications of Tandem mass spectrometry

Introduction to mass spectrometry/mass spectrometry - history of mass spectrometry/mass spectrometry, concepts and principles, nomenclature MS/MS instrumentation - principles of charged-particle analysis, sector-based MS/MS instruments, quadrupole instruments, hybrid instruments, MS/MS with ion-trapping techniques, reaction regions reactions in MS/MS - unimolecular dissociation, activation reactions reactive collisions, charge permutation reactions applications of MS/MS to fundamental studies - ion structures, reaction meachanisms, thermochemistry characteristics of MS/MS for analytical applications - sample considertions, choice of ionization method, interpretation of MS/MS spectra analytical applications - environmental applications, natural products applications, industrial products applications, foods and flavours applications, forensic chemistry applications, petroleum and petroleum products applications, bioorganic applications, pharmaceutical applications, applications to continuos flow samples and processes conclusions and outlook - instrumentation in MS/MS, outlook for advanced applications, interpretation of MS/MS data, conclusions. Appendices: MS/MS scan modes on various instrument configurations frequently used symbols and acronyms.

Tandem Mass Spectrometry of Small, Multiply Charged Oligonucleotides

Multiply charged anions derived from electrospray ionization of the sodium salts of various small oligonucleotides (n = 4−8) have been subjected to tandem mass spectrometry (MS/MS) in a quadrupole ion trap. All ions were observed to dissociate with high efficiencies even under conditions not ordinarily conducive for the observance of high MS/MS efficiency. Large fractions of the total product ion signal could be attributed to single-cleavage reactions with the parent ion charge shared among the two product ions in various combinations. In every case, the most facile reaction was observed to be the loss of the adenine anion. This reaction was then observed to be followed by cleavage of the 3′ C–O bond of phosphodiester linkage of the sugar from which the adenine had been lost.

Ion trap mass spectrometry

The quadrupole ion trap is a mass spectrometer whose essential components can be held in one hand. But it has a mass range of about 105 daltons per charge, provides molecular weight and structural information on biopolymers, and has the greatest sensitivity of all mass spectrometers. These features, however, have become available only within the past few years. They stem from an almost neglected 1958 invention, one in which interest was maintained by only a few research groups, notably those of John Todd at the University of Kent in England and Ray March at Trent University in Canada. Development of a new scanning method by George Stafford and his coworkers of Finnigan Corp. provided the impetus that led Finnigan to introduce a commercial ion trap in 1983. Since then, the device has been transformed from a simple gas chromatography detector to a high-performance mass spectrometer. In the late 1950s, Wolfgang Paul and his coworkers at ...

The basics of mass spectrometry in the twenty-first century.

Enormous advances in our understanding of the chemistry underlying life processes have identified new targets for therapeutic agents. The discovery of effective therapeutics to address these targets is often accomplished through parallel synthetic and screening efforts. In almost all cases, what has enabled target identification and allowed parallel approaches to drug discovery to be effective are the development of either new analytical tools or the improvement of currently existing ones. Among these tools, mass spectrometry has evolved to become an irreplaceable technique in the analysis of biologically related molecules. This article will guide researchers in drug discovery through the basic principles of mass spectrometry.

Tandem mass spectrometry of alkali cationized polysaccharides in a quadrupole ion trap

Quadrupole ion trap mass spectrometry is used to study the linkage type dependent dissociation pathways of alkali-cationized disaccharides, mostly of the type glucosyl(1 → X)glucose (X = 1, 2, 3, 4, or 6). The reaction mechanisms of a set of disaccharides containing all possible α anomeric linkage types and some β anomers are probed with tandem mass spectrometry, MSn, and double resonance experiments. Tandem mass spectrometry experiments on an 18O-labeled disaccharide show that the dissociation paths for Li and Na cationized species are the same. Experiments on three trisaccharides (isomaltotriose, maltotriose, and panose), a tetrasaccharide (isomaltotetraose), and a pentasaccharide (maltopentaose) show that tandem mass spectrometry provides all available linkage information and MSn can provide selected linkage information. The mode of alkali binding is examined via semiempirical calculations and by measuring alkali-carbohydrate relative cation affinities.

Ion isolation and sequential stages of mass spectrometry in a quadrupole ion trap mass spectrometer

Sequential reactions with as many as eleven steps (MS12) are accomplished with a quadrupole ion trap mass spectrometer. Both collision induced dissociation and ion/molecule reactions can be utilized in these reaction sequences. The isolation of intermediate products is performed extremely rapidly through the application of a combination of d.c. and r.f. potentials to give, to the ions of interest, coordinates near a cusp of the stability diagram (az = 0.150, qz = 0.781). The ion yields and signal-to-noise (S/N) ratios can be quite high for each individual step, resulting in good ultimate yields and S/N ratios even after multiple reaction steps. The scan functions used are investigated in detail by exploring the ejection of xenon isotopes in experiments which reveal the shape of the stability diagram in the cusp region. The resolution of the isolation procedure is investigated. These ion isolation capabilities are applied in a series of steps to cause extensive dissociation of the saturated sterane, cholestane, to yield a stable aromatic ion, C6H+5, and to demonstrate that the m/z 79 fragment of dimethylpyrrole is protonated benzene. They also allow multiple charge exchange and dissociation reactions to be performed in sequence on a single population of molecular ions.

Quantification of human uridine-diphosphate glucuronosyl transferase 1A isoforms in liver, intestine, and kidney using nanobore liquid chromatography-tandem mass spectrometry.

Uridine-disphosphate glucuronosyl transferase (UGT) enzymes catalyze the formation of glucuronide conjugates of phase II metabolism. Methods for absolute quantification of UGT1A1 and UGT1A6 were previously established utilizing stable isotope peptide internal standards with liquid chromatography-tandem mass spectrometry (LC-MS/MS). The current method expands upon this by quantifying eight UGT1A isoforms by nanobore high-performance liquid chromatography (HPLC) coupled with a linear ion trap time-of-flight mass spectrometer platform. Recombinant enzyme digests of each of the isoforms were used to determine assay linearity and detection limits. Enzyme expression level in human liver, kidney, and intestinal microsomal protein was determined by extrapolation from spiked stable isotope standards. Intraday and interday variability was <25% for each of the enzyme isoforms. Enzyme expression varied from 3 to 96 pmol/mg protein in liver and intestinal microsomal protein digests. Expression levels of UGT1A7, 1A8, and 1A10 were below detection limits (<1 pmol/mg protein) in human liver microsome (HLMs). In kidney microsomes the expression of UGT1A3 was below detection limits, but levels of UGT1A4, 1A7, 1A9, and 1A10 protein were higher relative to that of liver, suggesting that renal glucuronidation could be a significant factor in renal elimination of glucuronide conjugates. This novel method allows quantification of all nine UGT1A isoforms, many previously not amenable to measurement with traditional methods such as immunologically based assays. Quantitative measurement of proteins involved in drug disposition, such as the UGTs, significantly improves the ability to evaluate and interpret in vitro and in vivo studies in drug development.

Kinetic energy effects in mass spectrometry/mass spectrometry using a sector/quadrupole tandem instrument

Abstract Using a new hybrid (magnet/quadrupole) tandem mass spectrometer the effects of ion kinetic energy and target mass upon energy deposition have been investigated. In the range 1–100 eV, the degree of fragmentation is very sensitive to changes in the translational energy of the parent ion. Comparisons with MS/MS spectra recorded for the same ions (protonated 5-indanol, protonated diethylamine) using other instruments show that less significant changes in spectra occur in the kV energy range. Plots of branching ratios for competitive collision-induced dissociation channels against collision energy (1–100 eV) resemble, qualitatively, breakdown curves displaying ion abundances versus internal energy. In addition, comparisons of the effect of collision energy are made with spectral changes resulting from selection of the scattering angle in kV energy collisions. It is evident that translational energy selection is a counterpart, for spectrometers operating at low translational energy, of angle-resolved mass spectrometry.

Coupling of an atmospheric-samling ion source with an ion-trap mass spectrometer☆

Abstract An atomospheric-sampling glow-discharge ionization source has been interfaced with an ion-trap mass spectrometer. Under optimum conditions, the efficiency of ion injection is 1–5%. Several factors have a significant effect on the ion injection efficiency, including the voltages on the three-element lens system situated between the ion-source exit and the ion-trap entrance end-cap, the pressure of the bath gas present in the ion-trap vacuum housing, the nature of the bath gas and the amplitude of the radiofrequency voltage applied to the ring electrode during ion injection. Collision-induced dissociation (and electron detachment from anions) is also observed for some ions on injection, depending on the conditions. The most important experimental variables in determining the extent to which dissociation (or electron detachment) occurs are the nature of the bath gas, the bath gas presure and the radiofrequency voltage applied to the ring electrode during injection. These effects are illustrated with data obtained for polyatomic anions injected from the golw-discharge ion source.

Selective ion isolation/rejection over a broad mass range in the quadrupole ion trap

Techniques are presented for mass-selective ion manipulation over a wide mass range in a three-dimensional quadrupole. The methods use an auxiliary, low-amplitude radio-frequency signal applied to the endcap electrodes. This signal is either held at a single frequency as the fundamental radio-frequency trapping amplitude is ramped or swept over a frequency range while the fundamental radio-frequency trapping amplitude is held at a fixed level. Ion isolation and ejection are demonstrated for ions formed within the ion trap using electron ionization and for ions injected into the ion trap formed either by an air-sustained glow discharge or by electrospray. Mass-selective ion ejection is used to reduce matrix-ion-induced space charge during ion injection, thereby producing signal enhancement for the detection of 2, 4, 6-trinitrotoluene in air. Mass-selective isolation of ions with mass-to-charge ratios above the normal operating range (m / z 650) for the ion trap is also demonstrated after injection of myoglobin ions formed via electrospray.