Gas-phase reactivity of aromatic carbon-centered σ,σ-type biradicals toward oligonucleotides of differing lengths and comparison of the reactivity of charged phenyl radicals in solution and in the gas phase

Fanny Widjaja, Purdue University

Abstract

The biological activity the enediyne antitumor agents was suggested to arise from formation of aromatic carbon-centered σ,σ-type biradicals, which cause irreversible damage to double stranded DNA. Knowledge on the reactivity of aromatic carbon-centered σ,σ-type biradical intermediates is needed to facilitate the rational design of a more selective synthetic antitumor drugs. Gas-phase experiments allow for studies of these biradical intermediates in a solvent-free enviroment, which eliminates unwanted reactions with reagents other than those of interest. By utilizing the distonic ion approach, gas-phase reactivity of aromatic carbon-centered σ,σ-type biradicals toward oligonucleotides of differing length were examined in a Fourier-transform ion cyclotron resonance (FT-ICR) mass spectrometer coupled with laser-induced acoustic desorption (LIAD). This study demonstrates that when the biradicals were allowed to react with oligonucleotides of greater lengths, a drastic change in chemistry is observed, that is likely related to a conformational change of the oligonucleotides in the gas phase. While gas-phase experiments have been used to explore solution phenomena, correlation between the reactions observed in the gas phase and in solution needs to be studied thoroughly. Therefore, direct comparison of the reactivity of three isomeric charged pyridine-based radicals toward tetrahydrofuran and methanol in solution and in the gas phase were presented. In these studies, similar reactions were observed in solution and in the gas-phase and the insights obtained from gas phase study were found to be true in solution.

Degree

Ph.D.

Advisors

Kenttamaa, Purdue University.

Subject Area

Chemistry|Analytical chemistry|Organic chemistry

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