This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. This collaboration is aimed at the understanding of unusual patterns of fragmentation that arise in the general area of proximity effects by a combined approach using experimental and theoretical methods. One study deals with rearrangements of protonated molecules in the gas phase compared to condensed phase, which is an area where few precedents exist. Precursor ion formation was accomplished by either electrospray (ESI), fast atom bombardment (FAB) or chemical (CI) ionization. Rearrangements and fragmentations were induced by tandem MS/MS methods and interrogated isotopic labeling, model compounds, and corroborated by theoretical calculations. Rearrangements and fragmentation of target classes of compounds that have been studied so far include: N-(2-benzoyloxyphenyl) benzamide and substituted analogues;4- and 2-nitrophenylphenyl ether, thioether, and amine analogues;various chalcones e.g. 2-(o-methoxy or o-hydroxyphenyl)-vinyl phenyl ketones and related compounds, 2,4-dinitrophenylphenyl ethers and amines, and N-(2,4-dinitrophenyl)-analine or phenylanaline and analogues.