For proteins of <20 kDa, this new radical site dissociation method cleaves different and many more backbone bonds than the conventional MS/MS methods (e.g., collisionally activated dissociation, CAD) that add energy directly to the even-electron ions. A minimum kinetic energy difference between the electron and ion maximizes capture; a 1 eV difference reduces capture by 103. Thus, in an FTMS ion cell with added electron trapping electrodes, capture appears to be achieved best at the boundary between the potential wells that trap the electrons and ions, now providing 80 ± 15% precursor ion conversion efficiency. Capture cross section is dependent on the ionic charge squared (z2), minimizing the secondary dissociation of lower charge fragment ions. Electron capture is postulated to occur initially at a protonated site to release an energetic (∼6 eV) H• atom that is captured at a high-affinity site such as −S−S− or backbone amide to cause nonergodic (before energy randomization) dissociation. Cleavages betwe...

Electron Capture Dissociation for Structural Characterization of Multiply Charged Protein Cations

An overview of methods for preparing nanoparticles in the vapor phase is given, and recent advances are reviewed Developments in instrumentation for monitoring vapor-phase synthesis of nanoparticles and in modeling these processes are also included The most important developments relate to improved control and understanding of nanoparticle aggregation and coalescence during synthesis, and to methods for producing multi-component nanoparticles

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Vapor-phase synthesis of nanoparticles

1.1. Historical Background Hydrogen bonds1,2 are one of the principal intermolecular forces. A special class are ionic hydrogen bonds (IHBs) that form between ions and molecules with bonds strengths of 5-35 kcal/mol, up to a third of the strength of covalent bonds. These strong interactions are critical, for example, in ionic clusters and nucleation, in electrolytes, ion solvation, and acid-base chemistry, in the structures of ionic crystals, surfaces, silicates, and clays, in surface adsorption, and in self-assembly in supramolecular chemistry and molecular crystals.3 IHBs are also important in bioenergetics including protein folding, enzyme active centers, formation of membranes and proton transport, and biomolecular recognition. With such wide-ranging roles, the fundamental properties of IHB interactions need to be understood. The energetics of IHB interactions cannot be isolated and quantified in the condensed phase. However, these interactions can be isolated and studied quantitatively in gas phase. These studies lead to a fundamental understanding of relations between IHB bond strengths and molecular structure, the solvation of ions, especially in the critical inner shells, and acid-based phenomena and bioenergetics. This review will present the basic insights that have been obtained in the past four decades. It will present a comprehensive review of the thermochemistry and its structural implications obtained from ab initio calculations. Relevant recent results from spectroscopy will be also illustrated. The advent of variable temperature high-pressure mass spectrometry (HPMS) introduced by Field and co-workers in the 1960s4 and pulsed high-pressure mass spectrometry (PHPMS) introduced by Kebarle in the late 1960s5 have been particularly significant. These workers realized that at pressures of several torrs and gas densities of 1016-1017 cm-3 in ion sources, ions can undergo 103-106 collisions with neutral molecules during typical residence times of 0.1-10 ms and establish thermal ion populations and * E-mail: m.mautner@solis1.com. 213 Chem. Rev. 2005, 105, 213−284

http://www.astro-ecology.com/PDFTheIonicHydrogenBondChemicalReviews2005Paper.pdf

The Ionic Hydrogen Bond

Disulfide bonds in gaseous multiply-protonated proteins are preferentially cleaved in the mass spectrometer by low-energy electrons, in sharp contrast to excitation of the ions by photons or low-energy collisions. For S−S cyclized proteins, capture of one electron can break both an S−S bond and a backbone bond in the same ring, or even both disulfide bonds holding two peptide chains together (e.g., insulin), enhancing the sequence information obtainable by tandem mass spectrometry on proteins in trace amounts. Electron capture at uncharged S−S is unlikely; cleavage appears to be due to the high S−S affinity for H• atoms, consistent with a similar favorability found for tryptophan residues. RRKM calculations indicate that H• capture dissociation of backbone bonds in multiply-charged proteins represents nonergodic behavior, as proposed for the original direct mechanism of electron capture dissociation.

Electron Capture Dissociation of Gaseous Multiply-Charged Proteins Is Favored at Disulfide Bonds and Other Sites of High Hydrogen Atom Affinity

High-resolution spectroscopy of cluster ions.

The present invention is a method and apparatus for the synthesis of multi-component substances, comprising entities of at least two elements, molecules, grains, crystals, structural units, or phases of matter, in which the scale of the distribution of the elements, molecules, or phases of matter may range from on the order of nanometers or less, to about one millimeter, depending upon the specific materials and process conditions that are chosen. The method and apparatus of the present invention further provides processes for preparing these compositions of matter as thin films or particles.

Multi-component substances and processes for preparation thereof

Some novel ion-molecule chemistry within van der Waals clusters

Observation of intramolecular ion-molecule reactions within ionized clusters: the methyl halide systems

. We report the observation of laige (n up to -25) acetylene and methy-lacetylene cluster ions- the largest yet reported from ionization of neutral(C2H 2 )n or (CH 3 CCH)n clusters. The cluster ion intensity distributions of bothsystems display prominent magic numbers at n = 3. This finding is indicativeof Intracluster ion-molecule reactions giving rise to what are most likely ben-zene and trlmethylbenzene ions from (C2H2)n+ and (CH3CCH)n + cluster ions,respectively. The acetylene cluster Ion intensity distributions observed underefficient clustering conditions are further characterized by unexpected fea-tures, most notably a sharp break at n = 7 and a strong magic number at n= 14. The mass spectra of methylacetylene display a less dramatic break at n = 7and a weak magic number around n = 10. These surprising structures mayarise as a result of the formation of particularly stable covalently bondedmolecular ions. In view of the unique properties of carbon it is possible thatthese ions possess spherical cage geometries reminiscent of the fullerenes.t Alfred P Sloan Fbundation Fellow 1991-3.

http://www.researchgate.net/profile/James_Garvey3/publication/231403188_Intracluster_polymerization_reactions_within_acetylene_and_methylacetylene_clusters_ions/links/0912f50ef1c7b9abe5000000.pdf

James F. Garvey

Papers

Multi-component substances and processes for preparation thereof

Some novel ion-molecule chemistry within van der Waals clusters

Observation of intramolecular ion-molecule reactions within ionized clusters: the methyl halide systems

Intracluster Polymerization Reactions within Acetylene and Methylacetylene Clusters Ions.

Probing the Structure and Reactivity Of Hydrogen-Bonded Clusters of the Type {M}n{H2O}H+, via the Observation of Magic Numbers