UV Photophysics of DNA and RNA
Nucleotides In Vacuo: Dissociation
Channels, Time Scales, and Electronic
Spectra
10
J. Mathias Weber, Jesse Marcum, and Steen Brøndsted Nielsen
Abstract
This chapter deals with the UV-induced fragmentation of mononucleotide and
oligonucleotide ions isolated in vacuo. We review gas-phase photodissociation
spectra of mononucleotides, single strands, double strands and quadruplexes,
and compare these with the corresponding spectra in solutions to consider
solvatochromic shifts. The role of multiple bases is considered within the
Frenkel exciton model that describes the electronic coupling between two or
more bases, which is relevant to understand photoexcitation. We discuss relaxation of the excited states and the time scales for nucleotide dissociation when
there is no solvent quenching of the excess energy. Finally, the photophysical
behaviour of DNA with respect to electron ejection will be discussed with an
emphasis on the functional groups involved in electron loss.
10.1 Introduction
The photohysics of DNA is important for the understanding of deleterious processes that can ultimately cause skin cancer. Fortunately, this outcome of UV
exposure of skin is relatively unlikely due to the high photostability of DNA with
J.M. Weber (*)
JILA and Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO
80309-0440, USA
e-mail: weberjm@jila.colorado.edu
J. Marcum
Department of Chemistry and Food Science, Framingham State University, 100 State Street,
Framingham, MA 01701-9101, USA
S. Brøndsted Nielsen
Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, 8000 Aarhus C,
Denmark
e-mail: sbn@phys.au.dk
S. Brøndsted Nielsen and J.A. Wyer (eds.), Photophysics of Ionic Biochromophores,
Physical Chemistry in Action, DOI 10.1007/978-3-642-40190-9_10,
# Springer-Verlag Berlin Heidelberg 2013
181
Nucleotides In Vacuo: Dissociation
Channels, Time Scales, and Electronic
Spectra
10
J. Mathias Weber, Jesse Marcum, and Steen Brøndsted Nielsen
Abstract
This chapter deals with the UV-induced fragmentation of mononucleotide and
oligonucleotide ions isolated in vacuo. We review gas-phase photodissociation
spectra of mononucleotides, single strands, double strands and quadruplexes,
and compare these with the corresponding spectra in solutions to consider
solvatochromic shifts. The role of multiple bases is considered within the
Frenkel exciton model that describes the electronic coupling between two or
more bases, which is relevant to understand photoexcitation. We discuss relaxation of the excited states and the time scales for nucleotide dissociation when
there is no solvent quenching of the excess energy. Finally, the photophysical
behaviour of DNA with respect to electron ejection will be discussed with an
emphasis on the functional groups involved in electron loss.
10.1 Introduction
The photohysics of DNA is important for the understanding of deleterious processes that can ultimately cause skin cancer. Fortunately, this outcome of UV
exposure of skin is relatively unlikely due to the high photostability of DNA with
J.M. Weber (*)
JILA and Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO
80309-0440, USA
e-mail: weberjm@jila.colorado.edu
J. Marcum
Department of Chemistry and Food Science, Framingham State University, 100 State Street,
Framingham, MA 01701-9101, USA
S. Brøndsted Nielsen
Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, 8000 Aarhus C,
Denmark
e-mail: sbn@phys.au.dk
S. Brøndsted Nielsen and J.A. Wyer (eds.), Photophysics of Ionic Biochromophores,
Physical Chemistry in Action, DOI 10.1007/978-3-642-40190-9_10,
# Springer-Verlag Berlin Heidelberg 2013
181