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provided by Elsevier - Publisher Connector BOOK REVIEW Report of the 24th Asilomar Conference on

Jennifer S. Brodbelta and Alan G. Marshallb a Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, Texas, USA b National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida, USA

his Asilomar Conference reprises and updates an charge state for maximally informative peptide dissocia- Asilomar Conference of similar subject held in tion. Ryan Julian (University of California, Riverside) T1992. The program was well balanced with 25 introduced radical covalent labeling of peptides as a talks and 25 posters from a diverse range of participants means of inducing specific cleavages at the labeled amino and the conference was enhanced by the scenic coastal acid residue. site and spectacular weather. The Conference opened Carlito Lebrilla (University of California, Davis) gave with an overview by Alan Marshall, who noted that a comprehensive review of mass analysis of roughly 200 optimal performance requires attention to every stage glycans in milk and how their relative abundances can of the experiment: ionization (such as the use of more be correlated to diet and disease. Carol Nilsson (Pfizer, basic solvent to extend electrospray negative ionization Inc.) discussed how to isolate and identify phosphopro- to nonpolar analytes, including polycyclic aromatic teins and the site(s) of phosphorylation for glioblastoma hydrocarbons), ion accumulation, mass selection, ion cells (the most virulent type of brain cancer). Ljiljana transmission, ion trapping, signal generation and detec- Pasa-Tolic (Pacific Northwest National Laboratory) ex- tion, data reduction (such as phase correction for up to plained how best to combine high-pressure reversed- a 2-fold increase in mass resolving power), and various phase liquid chromatography and ultrahigh-resolution ion dissociation techniques. Eugene Nikolaev (The In- mass analysis for and also introduced a new stitute for Energy Problems) pointed out that if the multisegmented trapping cell for improved Fourier trans- number of trapped ions is sufficiently high, then their form-ion cyclotron resonance (FT-ICR) performance. space charge potential can become comparable to voltages In a preview of the 2009 Asilomar Conference on applied to trap electrodes. Single-ion simulation no longer Mass Spectrometry (Ion Spectroscopy, organized by suffices and it becomes necessary to model the behavior of Robert C. Dunbar and Thomas Baer, October 16–20, a million or more ions simultaneously with a supercom- 2009), two talks dealt with spectroscopy of gas-phase puter. He then showed how best to separately calculate ions. The main difficulty is that the gas-phase ion the potential contributions from the boundary electrodes, Ϫ concentration is approximately 10 15 M, so that absorp- image charge, and ion–ion interactions. tion cannot be detected directly. Rebecca Jockusch (Uni- Jenny Brodbelt introduced a novel peptide N-terminal derivatization strategy based on an isothiocyanate reagent versity of Toronto) presented early results on direct that effectively eliminates N-terminal (“b”) ions to leave detection of fluorescence of gas-phase rhodamine G only C-terminal (“y”) ions, thereby avoiding and elim- ions; the background is effectively zero, for greatly inating redundant sequence ions in identification of enhanced sensitivity. In a different approach, Valerie (MS/MS) product ions. Gabelica (Université de Liège) indirectly detected opti- James Reilly (Indiana University) discussed the use of cal absorption, based on ion dissociation induced by vacuum UV photons for photodissociation of peptides absorption of one (UV) or many (IR) photons, and and glycans, relative to the goal of achieving specific demonstrated base-stacking in single-strand and base- cleavages. Scott McLuckey (Purdue University) surveyed pairing and base-stacking in duplex DNA. various instrumental and chemical techniques and appli- Christopher Hendrickson (National High Magnetic cations for ion–ion reactions. The different dissociation Field Laboratory, Florida State University) used SIMION patterns for different charge stages can guide the choice of analysis to explain and optimize FT-ICR signal-detection sensitivity, and reduction of trapping and magnetron Address reprint requests to Dr. Jennifer S. Brodbelt, University of Texas at sidebands, by appropriate segmentation of the excitation, Austin, Department of Chemistry and Biochemistry, 1 University Station detection, and trapping electrodes. Alexander Makarov A5300, Austin, TX 78712-0165. E-mail: [email protected] Sponsored by the American Society for Mass Spectrometry, New Methods, (Thermo Fisher Scientific) gave a survey of recent devel- Instrumentation and Applications of Ion Traps, 24th Asilomar Conference opments in orbitrap MS, including various hybrid instru- on Mass Spectrometry, Friday, October 10 through Tuesday, October 14, 2008, Asilomar Conference Center, Pacific Grove, CA. Organized by Jen- ments designed to optimize collision-induced dissociation nifer Brodbelt and Alan Marshall. (CID) efficiency as well as deliberate distortion of the

Published online October 25, 2008 © 2009 Published by Elsevier Inc. on behalf of American Society for Mass Spectrometry. 1044-0305/09/$32.00 doi:10.1016/j.jasms.2008.10.014 R2 BRODBELT AND MARSHALL J Am Soc Mass Spectrom 2009, 20, R1–R3

Figure 1 harmonic trapping potential to reduce the effects of space ionization (by electrospray or simply by applying 3 kV charge. to the surface on which the sample is deposited) for James Hager (MDS Analytical Technologies) re- application to top-down proteomics, O-linked glycans, ported recent advances in a linear quadrupole ion trap, and tissue imaging. based on a combination of radial excitation and a Donald Douglas (University of British Columbia) modified fringing electric field and an additional dc detailed the addition of a few percent multipole fields axial field for faster scan rate and significantly im- (such as hexapole and octopole) to a linear quadrupole proved sensitivity. James Bruce (University of Washing- ion trap, by changing the relative size or relative rota- ton) presented several improvements in FT-ICR ion tional angle of adjacent quadrupole rods, for a 5- to manipulation, including an “inchworm” technique to 50-fold increase in MS/MS fragmentation efficiency. Jae convey ions from an external ion trap to the ICR cell Schwartz (Thermo Fisher Scientific) discussed a dual- with greatly suppressed time-of-flight mass discrimina- cell linear quadrupole ion trap configuration, for im- tion, concentric ring segmentation of the end cap elec- proved trapping efficiency and CID efficiency in the trodes for more quadrupolar trapping potential, and first high-pressure trap and higher-resolution detection improved resolution by introduction of an axial elec- in the second low-pressure trap. Both traps have slots in tron beam during detection. all four rods, for improved electric field symmetry. Li Evan Williams (University of California, Berkeley) Ding (Shimadzu Research Laboratory) also dealt with discussed preparation and infrared single-photon dis- two coupled quadrupole ion traps for MS/MS, but in sociation of hydrated ions in nanodroplets as a bridge this case with square wave rather than sinusoidal rf between bare ions and bulk solution to characterize voltage. Advantages include more efficient injection of solvation shells. By changing the charge state of a ions (or electrons, for ECD) into the trap by timing the hydrated ion by electron capture dissociation (ECD; entry during the period when the waveform voltage is gas-phase electrochemistry), Williams interprets the en- zero, as well as rapid MS/MS precursor ion selection suing reorganization of the ion hydration shell (hy- and wider product ion m/z range. drated ion nanocalorimetry) to propose a gas-phase Zheng Ouyang (Purdue University) began by describ- electrochemical absolute redox scale. The next two ing MS/MS based on simultaneous isolation of precursor speakers presented techniques designed to separate ions of more than one m/z value. He then analyzed and desorption and ionization to optimize the production of quantitated the higher surface smoothness required for gas-phase ions. Hilkka Kenttämaa (Purdue University) increasingly miniaturized quadrupole ion traps. Finally, described laser-induced acoustic desorption/chemical he used a pinched valve “shutter” as a discontinuous ionization as a means to achieve uniformly high ioniza- atmospheric pressure interface for improved MS perfor- tion efficiency for nonpolar species such as aliphatic mance with a linear quadrupole ion trap. and polycyclic aromatic hydrocarbons, for their suc- Gary Glish (University of North Carolina, Chapel cessful quantitation in petroleum by mass spectrome- Hill) showed that infrared multiphoton dissociation in a try. David Muddiman (North Carolina State University) quadrupole ion trap can be made mass-selective by described atmospheric pressure neutral desorption combining selective ion axial excitation with axially (with a laser, even without a MALDI matrix) and displaced laser irradiation. He also described a hybrid J Am Soc Mass Spectrom 2009, 20, R1–R3 BOOK REPORT R3 instrument in which ECD is conducted in a linear tide structure and hydrophobic/hydrophilic residue quadrupole trap inside a small magnet. From large-scale distribution, auguring the possibility to infer peptide survey data, Joshua Coon (University of Wisconsin, Mad- and protein structure (not just sequence and post- ison) used complementary data from CID and ETD to translational modifications) from ECD or ETD MS/MS. identify the nature and sites of post-translational modifi- Although ECD and ETD share many similarities, ECD cations (e.g., phosphorylation, methylation, acetylation) detected by FT-ICR and ETD in a multipole ion trap by MS/MS of proteins (e.g., preferential cleavage at pro- give different product ions as a result of the effect of line by CID but no cleavage by ETD) and applied them to ion-neutral collisions in ETD. identifying new phosphorylation “motifs” associated with The 24th Asilomar Conference on Mass Spectrome- particular biological recognition processes. He also try was fully subscribed, with 119 attendees. Poster showed that, with sufficiently high mass accuracy, it presentations ranged from X-ray diffraction of gas- becomes possible to distinguish N-terminal (b or c) phase ions to various ion trap configurations to various from C-terminal (y or z) peptide MS/MS product ions biological applications too numerous to describe here. according to whether the number of nitrogen plus Additional support provided by Applied Biosystems/ hydrogen atoms is even or odd. Yury Tsybin (Ecole MDS Analytical Technologies, Shimadzu, Waters Cor- Polytechnique Fédérale de Lausanne) correlated char- poration, and Thermo Scientific greatly enhanced the acteristic ECD/ETD fragmentation patterns with pep- Conference. (Figure 1).