@article {2333,
	title = {Dipole excitation of ions in linear radio frequency quadrupole ion traps with added multipole fields},
	journal = {International Journal of Mass Spectrometry},
	volume = {275},
	number = {1-3},
	year = {2008},
	note = {ISI Document Delivery No.: 338OVTimes Cited: 1Cited Reference Count: 35Zhao, XianZhen Douglas, D. J.},
	month = {Aug},
	pages = {91-103},
	type = {Article},
	abstract = {Ion motion with auxiliary dipole excitation and collisional damping in a linear radiofrequency quadrupole ion trap incorporating small amounts of even higher order multipoles is studied analytically. The ion motion is modeled in a pseudopotential that is mostly quadratic with small amounts of higher spatial harmonics. Ion motion along x and y axes is characterized by two uncoupled forced and damped anharmonic oscillator equations. A multiple time scales method is used to solve the equations of motion of ions with a first order perturbation Correction. Analytical relations between the oscillation amplitudes at steady state (the stationary amplitudes) and excitation frequency are calculated. The frequency response Curves show that in some cases bistable behavior might be obtained, i.e., there are two stable stationary amplitudes for a given excitation frequency. Crown Copyright (C) 2008 Published by Elsevier B.V. All rights reserved.},
	keywords = {BOUNDARY, higher order multipole, ion excitation, linear ion trap, MASS-SPECTROMETER, MOTION, nonlinear, OCTOPOLE FIELD, PAUL TRAPS, RESONANCE, RESONANCE EJECTION, SCAN, SIMULATION},
	isbn = {1387-3806},
	url = {<Go to ISI>://000258518200011},
	author = {Zhao, X. Z. and Douglas, D. J.}
}
@article {1414,
	title = {Multiple neutral loss monitoring (MNM): A multiplexed method for post-translational modification screening},
	journal = {Journal of the American Society for Mass Spectrometry},
	volume = {17},
	number = {3},
	year = {2006},
	note = {ISI Document Delivery No.: 021SETimes Cited: 11Cited Reference Count: 20},
	month = {Mar},
	pages = {307-317},
	type = {Article},
	abstract = {Post-translational modifications of proteins are involved in determining the activity of proteins and are essential for proper protein function. Current mass spectrometric strategies require one to specify a particular type of modification, in some cases also a particular charge state of a protein or peptide that is to be studied before the actual analysis. Due to these requirements, most of the modifications on proteins are not considered in such an experiment and, thus, a series of similar analyses need to be performed to ensure a more extensive characterization. A novel scan strategy has been developed, multiple neutral loss monitoring (MNM), allowing for the comprehensive screening of post-translational modifications (PTM) on proteins that fragment as neutral losses in a mass spectrometer. MNM method parameters were determined by performing product ion scans on a number of modified peptides over a range of collision energies, providing neutral loss energy profiles and optimal collision energies (OCE) for each modification, supplying valuable information pertaining to the fragmentation of these modifications and the necessary parameters that would be required to obtain the best analysis. As the optimal collision energy was highly dependent on the type of modification and the charge state of the peptide, the MNM scan was operated with a collision energy gradient. Autocorrelation analyses identified the type of modification, and convolution mapping analyses identified the associated peptide. The MNM scan with the new collision energy parameters was successfully applied to a mixture of four modified peptides in a BSA digest. The implementation of this technique will allow for comprehensive screening of all modifications that fragment as neutral losses.},
	keywords = {COLLISION-INDUCED DISSOCIATION, PEPTIDES, PROTEIN-PHOSPHORYLATION, PROTEOMIC ANALYSIS, SCAN, TANDEM MASS-SPECTROMETRY},
	isbn = {1044-0305},
	url = {<Go to ISI>://000236004700004},
	author = {Hoffman, M. D. and Sniatynski, M. J. and Rogalski, J. C. and Le Blanc, J. C. Y. and Kast, J.}
}
@article {1200,
	title = {Ion excitation in a linear quadrupole ion trap with an added octopole field},
	journal = {Journal of the American Society for Mass Spectrometry},
	volume = {16},
	number = {6},
	year = {2005},
	note = {ISI Document Delivery No.: 928AZTimes Cited: 17Cited Reference Count: 32},
	month = {Jun},
	pages = {835-849},
	type = {Article},
	abstract = {Modeling of ion motion and experimental investigations of ion excitation in a linear quadrupole trap with a 4 \% added octopole field are described. The results are compared with those obtained with a conventional round rod set. Motion in the effective potential of the rod set can explain many of the observed phenomena. The frequencies of ion oscillation in the x and y directions shift with amplitude in opposite directions as the amplitudes of oscillation increase. Excitation profiles for ion fragmentation become asymmetric and in some cases show bistable behavior where the amplitude of oscillation suddenly jumps between high and low values with very small changes in excitation frequency. Experiments show these effects. Ions are injected into a linear trap, stored, isolated, excited for MS/MS, and then mass analyzed in a time-of-flight mass analyzer. Frequency shifts between the x and y motions are observed, and in some cases asymmetric excitation profiles and bistable behavior are observed. Higher MS/MS efficiencies are expected when an octopole field is added. MS/MS efficiencies ((2) collision gas) have been measured for a conventional quadrupole rod set and a linear ion trap with a 4 \% added octopole field. Efficiencies are chemical compound dependent, but when an octopole field is added, efficiencies can be substantially higher than with a conventional rod set, particularly at pressures of 1.4 X 10(-4) torr or less. (c) 2005 American Society for Mass Spectrometry.},
	keywords = {EJECTION, MASS-SPECTROMETER, OF-FLIGHT SYSTEM, PAUL TRAP, RESONANT EXCITATION, SCAN, SIMULATION},
	isbn = {1044-0305},
	url = {<Go to ISI>://000229244800004},
	author = {Michaud, A. L. and Frank, A. J. and Ding, C. and Zhao, X. Z. and Douglas, D. J.}
}
