Chapter 6
Biomolecules, Photostability and 1 πσ ∗ States:
Linking These with Femtochemistry
Gareth M. Roberts and Vasilios G. Stavros
Abstract In an effort to illuminate why nature has chosen a particular set of biomolecular ‘building-blocks’ for life, a surge of gas phase experiments have recently
targeted understanding why key DNA bases, amino acids and their corresponding
chromophore subunits, exhibit a resistance to photochemical damage (photostability) following ultraviolet radiation absorption. The research considered in this chapter focuses on the role of dissociative 1 πσ ∗ states in photostable behavior, and in
particular H-atom elimination mediated via these states. By probing the timescales
for the appearance of these H-atoms using ultrafast lasers coupled to molecular
beam methodologies, important information pertaining to the excited state dynamics of these molecules can be obtained. We also discuss how the information gleaned
from these studies can be used as a ‘stepping-stone’ for extending this research to
larger, more complex biomolecules and, ultimately, more realistic systems in solution.
6.1 Introduction
Over the years a vast arena of interdisciplinary research has strived to understand
the important characteristics of many biomolecules at a molecular level. Recently
though, the contemporary discipline of ultrafast biophysics has led to a number of
important breakthroughs regarding our understanding of key biological processes.
This has been achieved by probing the excited electronic (and vibrational) state dynamics involved in these, often complex, natural systems [1]. Whilst this is not
intended to be an exhaustive list, this field has aided in intimately mapping the
trigger mechanism for human vision in rhodopsin [2, 3], efficient light harvesting
processes occurring within photosynthesis [4] and the origins of high fluorescence
quantum yields in numerous fluorescent protein variants [5, 6]. Such feats truly emphasize how probing the excited state dynamics of biological species on an ultrafast
G.M. Roberts · V.G. Stavros (B)
Department of Chemistry, University of Warwick, Library Road, Coventry CV4 7AL, UK
e-mail: v.stavros@warwick.ac.uk
G.M. Roberts
e-mail: g.m.roberts@warwick.ac.uk
R. de Nalda, L. Bañares (eds.), Ultrafast Phenomena in Molecular Sciences,
Springer Series in Chemical Physics 107, DOI 10.1007/978-3-319-02051-8_6,
© Springer International Publishing Switzerland 2014
119
Biomolecules, Photostability and 1 πσ ∗ States:
Linking These with Femtochemistry
Gareth M. Roberts and Vasilios G. Stavros
Abstract In an effort to illuminate why nature has chosen a particular set of biomolecular ‘building-blocks’ for life, a surge of gas phase experiments have recently
targeted understanding why key DNA bases, amino acids and their corresponding
chromophore subunits, exhibit a resistance to photochemical damage (photostability) following ultraviolet radiation absorption. The research considered in this chapter focuses on the role of dissociative 1 πσ ∗ states in photostable behavior, and in
particular H-atom elimination mediated via these states. By probing the timescales
for the appearance of these H-atoms using ultrafast lasers coupled to molecular
beam methodologies, important information pertaining to the excited state dynamics of these molecules can be obtained. We also discuss how the information gleaned
from these studies can be used as a ‘stepping-stone’ for extending this research to
larger, more complex biomolecules and, ultimately, more realistic systems in solution.
6.1 Introduction
Over the years a vast arena of interdisciplinary research has strived to understand
the important characteristics of many biomolecules at a molecular level. Recently
though, the contemporary discipline of ultrafast biophysics has led to a number of
important breakthroughs regarding our understanding of key biological processes.
This has been achieved by probing the excited electronic (and vibrational) state dynamics involved in these, often complex, natural systems [1]. Whilst this is not
intended to be an exhaustive list, this field has aided in intimately mapping the
trigger mechanism for human vision in rhodopsin [2, 3], efficient light harvesting
processes occurring within photosynthesis [4] and the origins of high fluorescence
quantum yields in numerous fluorescent protein variants [5, 6]. Such feats truly emphasize how probing the excited state dynamics of biological species on an ultrafast
G.M. Roberts · V.G. Stavros (B)
Department of Chemistry, University of Warwick, Library Road, Coventry CV4 7AL, UK
e-mail: v.stavros@warwick.ac.uk
G.M. Roberts
e-mail: g.m.roberts@warwick.ac.uk
R. de Nalda, L. Bañares (eds.), Ultrafast Phenomena in Molecular Sciences,
Springer Series in Chemical Physics 107, DOI 10.1007/978-3-319-02051-8_6,
© Springer International Publishing Switzerland 2014
119