Spectral line

Spectroscopy

Quantum mechanics

Magnetic circular dichroism

Phase (matter)

Linear dichroism

Chromatography

Laser

Physics

Organic chemistry

X-ray magnetic circular dichroism

Optics

Astronomy

Molecular physics

Circular dichroism

Nanosecond

Analytical Chemistry (journal)

Crystallography

Mass spectrometry

Chemistry

Vibrational circular dichroism

Dichroism

Absorption spectroscopy

Science

DNA and proteins are chiral: their three-dimensional structure cannot be superimposed with its mirror image. Circular dichroism spectroscopy is widely used to characterize chiral compounds, but data interpretation is difficult in the case of mixtures. We recorded for the first time the electronic circular dichroism spectra of DNA helices separated in a mass spectrometer. We electrosprayed guanine-rich strands having various secondary structures as negative ions, irradiated them with a laser, and measured the difference in electron photodetachment efficiency between left and right circularly polarized light. The reconstructed circular dichroism ion spectra resemble the solution ones, 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.

Mass-resolved electronic circular dichroism ion spectroscopy