Ion beams and laser postionization for molecule-specific imaging

Winograd, Nicholas

doi:10.1021/ac00062a001

Cited by 46 publications

(37 citation statements)

References 19 publications

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“…As an alternative to MALDI, the secondary ion mass spectrometry (SIMS) is also a powerful technique for structural characterization for synthetic polymers 14–17. Furthermore, SIMS can be applied to several micrometer scale imaging 14, 15. However, mass spectra are always associated with strong fragment ions and in many cases, intact molecular ions are absent in the mass spectra 17.…”

Section: Introductionmentioning

confidence: 99%

The analysis of industrial synthetic polymers by electrospray droplet impact/secondary ion mass spectrometry

2009

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Electrospray droplet impact (EDI)/secondary ion mass spectrometry (SIMS) is a new desorption/ionization technique for mass spectrometry in which highly charged water clusters produced from the atmospheric-pressure electrospray are accelerated in vacuum by several kV and impact the sample deposited on the metal substrate. In this study, several industrial synthetic polymers, e.g. polystyrene (PS) and polyethylene glycol (PEG) were analyzed by EDI/SIMS mass spectrometry. For higher molecular weight analytes, e.g. PS4000 and PEG4600, EDI/SIMS mass spectra could be obtained when cationization salts are added. For the polymers of lower molecular weights, e.g. PEG300 and PEG600, they could be readily detected as protonated ions without the addition of cationization agents. Anionized PS was also observed in the negative ion mode of operation when acetic acid was added to the charged droplet. Compared to matrix-assisted laser desorption/ionization (MALDI), ion signal distribution with lower background signals could be obtained particularly for the low-molecular weight polymers.

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Section: Introductionmentioning

confidence: 99%

The analysis of industrial synthetic polymers by electrospray droplet impact/secondary ion mass spectrometry

2009

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“…While considerable progress has been made in ionizing large molecular systems intact using electrospray and matrix-assisted laser desorption ionization (MALDI), mass spectrometric surface characterization has been less successful in this regard. Early efforts have focused on using nanosecond lasers to photoionize neutral species desorbed from surfaces by either an energetic ion beam − or another laser beam. − This approach has been successful in increasing overall ion yields, particularly in atomic systems. However, in molecular systems, the advantages gained in increased ion yields are often offset by extensive photoinduced fragmentation.…”

Section: Introductionmentioning

confidence: 99%

Femtosecond Photoionization of Ion Beam Desorbed Aliphatic and Aromatic Amino Acids: Fragmentation via α-Cleavage Reactions

et al. 1999

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We report the photoionization of ion beam desorbed amino acids using femtosecond laser pulses at 195 and 260 nm. Ionization of ion-desorbed glycine, alanine, valine, leucine, isoleucine, and phenylalanine using 195 nm laser pulses is found to produce almost exclusively a decarboxylated ion fragment, while tyrosine and tryptophan produce a functional group cation. The adiabatic ionization potentials for the former amino acids correspond to the removal of an electron from the amine nitrogen atom, while for tyrosine and tryptophan it corresponds to the removal of an electron from the aromatic functional group. We find that fragmentation is initiated by the formation of a radical site which leads to an α-cleavage reaction and, depending upon which electron is removed, results in the formation of a decarboxylated ion or a functional group ion. These results indicate that a significant fraction of the amino acids are desorbed intact, but are fragmented when ionized. Except for leucine, isoleucine, and phenylalanine, the mass spectra produced by 260 nm irradiation are similar to the mass spectra produced by 195 nm irradiation. When using these two wavelengths, the desorbed amino acids exhibit a 2- to 8-fold higher ion yield than is found using only secondary ions produced directly by the incident ion beam. Tyrosine exhibits up to a 40-fold increase in signal using 195 nm irradiation.

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“…However, the useful ion yield from pixels of that size range is limited due to the poor percentage of sputtered molecules from the sample surface. 31,41 The energetic desorption process associated with SIMS yields significant fragmentation of desorbed material. 42 Hence, SIMS has been most successful for inorganic molecules, low molecular weight biomolecules (< 1500 Da), or simply to acquire elemental distributions.…”

Section: Sims Imagingmentioning

confidence: 99%

Tip Enhanced Laser Ablation Sample Transfer for Mass Spectrometry

2015

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Mass spectrometry is one of the primary analysis techniques for biological analysis but there are technological barriers in sampling scale that must be overcome for it to be used to its full potential on the size scale of single cells. Current mass spectrometry imaging methods are limited in spatial resolution when analyzing large biomolecules. The goal of this project is to use atomic force microscope (AFM) tip enhanced laser ablation to remove material from cells and tissue and capture it for subsequent mass spectrometry analysis. The laser ablation sample transfer system uses an AFM stage to hold the metal-coated tip at a distance of approximately 10 nm from a sample surface. The metal tip acts as an antenna for the electromagnetic radiation and enables the ablation of the sample with a spot size much smaller than a laser focused with a conventional lens system. A pulsed nanosecond UV or visible wavelength laser is focused onto the gold-coated silicon tip at an angle nearly parallel with the surface, which results in the removal of material from a spot between 500 nm and 1 µm in diameter and 200 and 500 nm deep. This corresponds to a few picograms of ablated material, which can be captured on a metal surface for MALDI analysis. We have used this approach to transfer small peptides and proteins from a thin film for analysis by mass spectrometry as a first step toward high spatial resolution imaging.

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Ion beams and laser postionization for molecule-specific imaging

Cited by 46 publications

References 19 publications

The analysis of industrial synthetic polymers by electrospray droplet impact/secondary ion mass spectrometry

The analysis of industrial synthetic polymers by electrospray droplet impact/secondary ion mass spectrometry

Femtosecond Photoionization of Ion Beam Desorbed Aliphatic and Aromatic Amino Acids: Fragmentation via α-Cleavage Reactions

Tip Enhanced Laser Ablation Sample Transfer for Mass Spectrometry

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