Ion/surface reactions and ion soft-landing

The exposure of charged microdroplets containing organic ions to solid-phase reagents at ambient surfaces results in heterogeneous ion/surface reactions. The electrosprayed droplets were driven pneumatically in ambient air and then electrically directed onto a surface coated with reagent. Using this reactive soft landing approach, acid-catalyzed Girard condensation was achieved at an ambient surface by directing droplets containing Girard T ions onto a dry ketosteroid. The charged droplet/surface reaction was much more efficient than the corresponding bulk solution-phase reaction performed on the same scale. The increase in product yield is ascribed to solvent evaporation, which causes moderate pH values in the starting droplet to reach extreme values and increases reagent concentrations. Comparisons are made with an experiment in which the droplets were pneumatically accelerated onto the ambient surface (reactive desorption electrospray ionization, DESI). The same reaction products were observed but differences in spatial distribution were seen associated with the "splash" of the high velocity DESI droplets. In a third type of experiment, the reactions of charged droplets with vapor phase reagents were examined by allowing electrosprayed droplets containing a reagent to intercept the headspace vapor of an analyte. Deposition onto a collector surface and mass analysis showed that samples in the vapor phase were captured by the electrospray droplets, and that instantaneous derivatization of the captured sample is possible in the open air. The systems examined under this condition included the derivatization of cortisone vapor with Girard T and that of 4-phenylpyridine N-oxide and 2-phenylacetophenone vapors with ethanolamine.

Section: Introductionmentioning

confidence: 96%

Reactions of Microsolvated Organic Compounds at Ambient Surfaces: Droplet Velocity, Charge State, and Solvent Effects

Badu‐Tawiah

Campbell

Cooks

2012

“…SL is defined as intact capture of mass-selected polyatomic ions on substrates [6,7] and has already been successfully used to study charge retention by small closedshell ions [6 -9] and peptide and protein ions deposited onto self-assembled monolayer surfaces (SAMs) [10 -13]. Retention of biological activity (but not charge) by proteins deposited on liquid [10,14] and on plasma treated metal surfaces [15] has also been demonstrated.…”

mentioning

confidence: 99%

Effect of the surface on charge reduction and desorption kinetics of soft landed peptide ions

Hadjar

Wang

Laskin

2009

Self Cite

Charge reduction and desorption kinetics of ions and neutral molecules produced by soft-landing of mass-selected singly and doubly protonated Gramicidin S (GS) on different surfaces was studied using time dependant in situ secondary ion mass spectrometry (SIMS) integrated in a specially designed Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS) research instrument. Soft-landing targets utilized in this study included inert self-assembled monolayers (SAMs) of 1-dodecane thiol (HSAM) and its fluorinated analog (FSAM) on gold and hydrophilic carboxyl-terminated (COOH-SAM) and amine-terminated (NH 2 -SAM) surfaces. We observed efficient neutralization of soft-landed ions on the COOH-SAM surface, partial retention of only one proton on the HSAM surface, and efficient retention of two protons on the FSAM surface. For example, protein adsorption on substrates is a highly dynamic process that is strongly influenced by Coulomb interactions, hydrogen bonding, and relatively weak noncovalent interactions. These processes are highly dependant on the primary and the highorder structure of the protein and on the properties of the surface and the solvent.It has recently been demonstrated that soft-landing (SL) of mass-selected ions on surfaces is a useful mass spectrometric approach for probing details of this intrinsic behavior of immobilized biological molecules that removes the strong effects of solvents [3][4][5]. SL is defined as intact capture of mass-selected polyatomic ions on substrates [6,7] and has already been successfully used to study charge retention by small closedshell ions [6 -9] and peptide and protein ions deposited onto self-assembled monolayer surfaces (SAMs) [10 -13]. Retention of biological activity (but not charge) by proteins deposited on liquid [10,14] and on plasma treated metal surfaces [15] has also been demonstrated.Recently we reported the first detailed study of the kinetics of desorption and charge reduction following SL of doubly protonated Gramicidin S (GS) onto the FSAM surface [16]. We utilized an in-line 8 keV Cs ϩ ion gun that allowed us to interrogate the surface in situ and in real time using secondary ion mass spectrometry (SIMS). We followed the evolution of the SIMS spectrum as a function of time during and after the deposition of [GS ϩ 2H] 2ϩ and obtained unique kinetics signatures for doubly protonated, singly protonated, and neutral peptides retained on the surface. Using the characteristic ion signatures and a kinetic model we measured rate coefficients for charge reduction and thermal desorption of ions and neutral GS molecules from the surface. An important process established in that work was the instantaneous loss of one or two protons by a fraction of ions colliding with the FSAM surface. Collision induced fast charge reduction is followed by very slow proton loss by ions trapped on the surface. Thermal desorption of ionic and neutral species efficiently competes with the charge reduction process.In this research, we applied the same in situ SIMS tec...

“…It should be noted that ionsurface reactions can result in a number of chemically interesting phenomena and are not limited to surfaceinduced dissociation. Chemical sputtering, elastic and reactive ion scattering, and soft landing are all prevalent chemical processes that occur in the hyperthermal (1-100 eV) collision energy regime, and descriptions of each can be found in recent reviews [8,9]. The purpose of this article is to focus on ion-surface collisions as they pertain to ion activation, offering a perspective on SID and its application to various systems of interest and to present only a brief description of reactive ion scattering spectrometry (RISS).…”

mentioning

confidence: 99%

Surface-induced dissociation of small molecules, peptides, and non-covalent protein complexes

Wysocki

Joyce

Jones

et al. 2008

130

138

This article provides a perspective on collisions of ions with surfaces, including surfaceinduced dissociation (SID) and reactive ion scattering spectrometry (RISS). The content is organized into sections on surface-induced dissociation of small ions, surface characterization of organic thin films by collision of well-characterized ions into surfaces, the use of SID to probe peptide fragmentation, and the dissociation of large non-covalent complexes by SID. Examples are given from the literature with a focus on experiments from the authors' laboratory. The article is not a comprehensive review but is designed to provide the reader with an overview of the types of results possible by collisions of ions into surfaces. (J Am Soc Mass Spectrom 2008, 19, 190 -208) © 2008 American Society for Mass Spectrometry T andem mass spectrometry (MS/MS) is an essential tool for elucidating ion structure. The MS/MS experiment involves mass selection of a precursor ion followed by ion activation and subsequent dissociation. The ion activation step is commonly accomplished via collision-induced dissociation (CID) in which the initial kinetic energy of a projectile ion is converted into internal energy through inelastic collisions with a neutral gas. Several alternative activation methods have been used in tandem mass spectrometry, one of which is surfaceinduced dissociation (SID). SID is analogous to CID, except that a surface replaces the neutral gas as the collision target. A typical ion-surface collision event is illustrated in Figure 1.The incorporation of a surface into a mass spectrometer for ion activation was pioneered in the laboratory of R. Graham Cooks in the mid-1970s and early 1980s [1][2][3]. Since that time, collisions of lowenergy (eV) organic ions with surfaces within the tandem mass spectrometer have been valuable for analyzing surface composition, characterizing reactions between organic projectile ions and surface adsorbates, chemically modifying surfaces, and determining projectile ion structure. A major motivation for development of SID is that energy transfer to ionic projectiles can be improved by increasing the mass of the collision target. The total available energy for transfer into the internal modes of the projectile ion is defined by the center-of-mass energy (E COM ) described by eq 1:where E LAB is the laboratory collision energy and M ION and M N are the masses of the projectile ion and neutral, respectively. Energy transfer in CID is limited by the mass of the collision partner, typically inert gases such as helium, argon, or xenon. In SID, if one assumes that the surface is an infinitely large collision partner, E COM becomes independent of mass and approaches the laboratory collision energy. The assumption that the entire surface can be viewed as the collision partner is not always valid, however, and there are instances where the mass of the terminal groups on the surface influence the amount of energy transfer [4,5]. Nonetheless, the use of a massive surface target should, in theory, provide ...