Reactivity of aromatic sigma, sigma-biradicals toward riboses.
The gas-phase reactions of sugars with aromatic, carbon-centered sigma,sigma-biradicals with varying polarities [as reflected by their calculated electron affinities (EA)] and extent of spin-spin coupling [as reflected by their calculated singlet-triplet (S-T) gaps] have been studied. The biradicals are positively charged, which allows them to be manipulated and their reactions to be studied in a Fourier-transform ion cyclotron resonance mass spectrometer. Hydrogen atom abstraction from sugars was found to be the dominant reaction for the biradicals with large EA values, while the biradicals with large S-T gaps tend to form addition/elimination products instead. Hence, not all sigma, sigma-biradicals may be able to damage DNA by hydrogen atom abstraction. The overall reaction efficiencies of the biradicals towards a given substrate were found to be directly related to the magnitude of their EA values, and inversely related to their S-T gaps. The EA of a biradical appears to be a very important rate-controlling factor, and it may even counterbalance the reduced radical reactivity characteristic of singlet biradicals that have large S-T gaps.
Adeuya
Anthony
A
Department of Chemistry, Purdue University, West Lafayette, Indiana 47907-1393, USA.
Yang
Linan
L
Amegayibor
F Sedinam
FS
Nash
John J
JJ
Kenttämaa
Hilkka I
HI
D017357:Cyclotrons; D003627:Data Interpretation, Statistical; D005583:Fourier Analysis; D005609:Free Radicals; D006841:Hydrocarbons, Aromatic / Q000737:chemistry*; D007202:Indicators and Reagents; D013058:Mass Spectrometry; D012266:Ribose / Q000031:analogs & derivatives* / Q000737:chemistry*
D005609:Free Radicals; D006841:Hydrocarbons, Aromatic; D007202:Indicators and Reagents; D012266:Ribose