Electron photodetachment from transient negative ions in the multiphoton ionization of CH3I

DNA and proteins are chiral: Their three-dimensional structures cannot be superimposed with their mirror images. Circular dichroism spectroscopy is widely used to characterize chiral compounds, but data interpretation is difficult in the case of mixtures. We recorded the electronic circular dichroism spectra of DNA helices separated in a mass spectrometer. We studied guanine-rich strands having various secondary structures, electrosprayed them as negative ions, irradiated them with an ultraviolet nanosecond optical parametric oscillator laser, and measured the difference in electron photodetachment efficiency between left and right circularly polarized light. The reconstructed circular dichroism ion spectra resembled those of their solution-phase counterparts, thereby allowing us to assign the DNA helical topology. The ability to measure circular dichroism directly on biomolecular ions expands the capabilities of mass spectrometry for structural analysis.

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Elucidating the initial dynamics of electron photodetachment from atoms in liquids using variably-time-delayed resonant multiphoton ionization

The Journal of Chemical Physics ◽

10.1063/1.1756874 ◽

2004 ◽

Vol 121 (1) ◽

pp. 374 ◽

Cited By ~ 9

Author(s):

Ignacio B. Martini ◽

Benjamin J. Schwartz

Keyword(s):

Multiphoton Ionization ◽

Electron Photodetachment

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Electron photodetachment from negative ions of C2v symmetry. Electron affinities of allyl and cyanomethyl radicals

Journal of the American Chemical Society ◽

10.1021/ja00453a004 ◽

1977 ◽

Vol 99 (11) ◽

pp. 3565-3568 ◽

Cited By ~ 39

Author(s):

Albert H. Zimmerman ◽

John I. Brauman

Keyword(s):

Negative Ions ◽

Electron Affinities ◽

Electron Photodetachment

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Spectrometric Characterization of Purified C60 and C70

MRS Proceedings ◽

10.1557/proc-206-679 ◽

1990 ◽

Vol 206 ◽

Cited By ~ 4

Author(s):

Keith R. Lykke ◽

Michael J. Pellin ◽

Peter Wurz ◽

Dieter M. Gruen ◽

Jerry E. Hunt ◽

...

Keyword(s):

Electronic Absorption ◽

Mass Spectra ◽

Fluorescence Spectra ◽

Multiphoton Ionization ◽

Negative Ions ◽

Picosecond Laser ◽

Laser Desorption ◽

Signal To Noise ◽

Neutral Species

ABSTRACTC60 and C70 were synthesized and purified according to published procedures. Both nanosecond and picosecond laser desorption from coated substrates gave copious positive and negative ions. Mass spectra (TOF and FTMS) with excellent signal to noise, showing only the C60 and C70 mass peaks, have been observed. Well-resolved isotopic structure was seen in the FTMS spectra in agreement with the natural abundance of carbon. Laser desorption and multiphoton ionization/photodissociation of the neutral species, as well as electronic absorption, FTIR, and fluorescence spectra, have been obtained.

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