Preparation and in Situ Characterization of Surfaces Using Soft Landing in a Fourier Transform Ion Cyclotron Resonance Mass Spectrometer

Alvarez, Jormarie; Cooks, R. Graham; Barlow, Stephan E.; Gaspar, Daniel J.; Futrell, Jean H.; Laskin, Julia

doi:10.1021/ac0481349

Cited by 60 publications

(130 citation statements)

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“…It should be noted that because SL of mass-selected ions produces highly pure uniform films on substrates it is difficult to compare our results with results obtained using conventional surface preparation methods. We have conducted extensive characterization of peptide films prepared using dried droplet and electrospray deposition approaches [11,12,21] and concluded that SIMS spectra obtained for such films are strongly affected by the presence of impurities and the morphology of the samples generated during the drying process. SIMS spectra obtained from peptide films prepared using these approaches are more complex than the corresponding spectra obtained from films prepared by SL.…”

Section: Resultsmentioning

confidence: 99%

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

Hadjar

Wang

Laskin

2009

J. Am. Soc. Mass Spectrom.

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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...

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Section: Resultsmentioning

confidence: 99%

“…The experimental approach for SL experiments has been described elsewhere [11,16]. Briefly, mass-selected peptide ions produced in a high-transmission electrospray source undergo normal-incidence collision with a SAM surface positioned at the rear trapping plate of the ICR cell.…”

Section: Methodsmentioning

confidence: 99%

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

Hadjar

Wang

Laskin

2009

J. Am. Soc. Mass Spectrom.

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“…It is normally assumed that the landed ion will retain its charge(s) but neutralization accompanying deposition/binding is also well known. Laskin has done much to elucidate the process of charge loss during and after the SL event [7]. The SL procedure not only alters the surface, but it also offers a new approach to preparative scale molecular separation and to molecular-level understanding of the interactions between molecules/ions and substrates relevant to biological, catalytic, and other applications [8,9].…”

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confidence: 99%

“…The first was a custom-built Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS) in which a beam of mass-selected ions of variable kinetic energy was used to modify surfaces via SL [7]. In situ analysis of the modified surfaces was achieved by 2 keV Cs ϩ secondary ion mass spectrometry (SIMS) with FT-ICR detection of the sputtered secondary ions (FT-ICR-SIMS).…”

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confidence: 99%

“…Laskin, Futrell, and colleagues recently reviewed the current understanding of the fundamental factors that affect SL of biomolecular ions onto inert and reactive SAMs [13]. SAMs are good substrates for SL because they can trap ions by dissipating kinetic energy and this was reflected in a dramatic increase in the ion yield in in situ SIMS analysis [7]. It is also interesting to note that a significant fraction of soft-landed peptide ions retain their charge, even after exposure of the surface to the ambient atmosphere, confirming a noteworthy earlier result [12].…”

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In situ SIMS analysis and reactions of surfaces prepared by soft landing of mass-selected cations and anions using an ion trap mass spectrometer

Nie

Goodwin

et al. 2009

J. Am. Soc. Mass Spectrom.

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Mass-selected polyatomic cations and anions, produced by electrosonic spray ionization (ESSI), were deposited onto polycrystalline Au or fluorinated self-assembled monolayer (FSAM) surfaces by soft landing (SL), using a rectilinear ion trap (RIT) mass spectrometer. Protonated and deprotonated molecules, as well as intact cations and anions generated from such molecules as peptides, inorganic catalysts, and fluorescent dyes, were soft-landed onto the surfaces. Analysis of the modified surfaces was performed in situ by Cs ϩ secondary ion mass spectrometry (SIMS) using the same RIT mass analyzer to characterize the sputtered ions as that used to mass select the primary ions for SL. Soft-landing times as short as 30 s provided surfaces that yielded good quality SIMS spectra. Chemical reactions of the surfaces modified by SL were generated in an attached reaction chamber into which the surface was transferred under vacuum. For example, a surface on which protonated triethanolamine had been soft landed was silylated using vapor-phase chlorotrimethylsilane before being returned still under vacuum to the preparation chamber where SIMS analysis revealed the silyloxy functionalization. SL and vapor-phase reactions are complementary methods of surface modification and in situ surface analysis by SIMS is a simple way to characterize the products produced by either technique. (J Am Soc Mass Spectrom 2009, 20, 949 -956)

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Ion Soft‐Landing of Permanently Charged Molecular Ions and Their Charge Retention on Surfaces

Warneke

Knorke²,

Charvát

et al. 2022

Encyclopedia of Inorganic and Bioinorganic Chemistry

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Ion soft‐landing, also often called “preparative mass spectrometry,” is a method that allows the deposition of mass‐selected ions onto surfaces without fragmentation. This technique is usually performed using a conductive deposition target. Generally, charge transfer to the surface results in the neutralization of the deposited ions. However, charge retention of the ions can also occur if the deposited ions are electronically very stable or the surface is covered by an insulating layer. The aim of this article is to introduce the reader to fundamental physical models, including detailed mathematical deviations, which contribute to the understanding of the interaction between a layer of deposited ions and approaching ions. First, a historical overview of the experimental evidence for charge retention of soft‐landed ions is given and the classes of molecular ions predominantly used in these studies are introduced. Subsequently, physical models are introduced, considering the influence of a variety of parameters including surface size, ionic layer size, distance between deposited ions, and thickness of insulating layers. Finally, the effects which become important above the monolayer coverage of ions are discussed.

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Preparation and in Situ Characterization of Surfaces Using Soft Landing in a Fourier Transform Ion Cyclotron Resonance Mass Spectrometer

Cited by 60 publications

References 34 publications

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

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

In situ SIMS analysis and reactions of surfaces prepared by soft landing of mass-selected cations and anions using an ion trap mass spectrometer

Ion Soft‐Landing of Permanently Charged Molecular Ions and Their Charge Retention on Surfaces

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