APPLICATION OF HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY MASS-SPECTROMETRY WITH ELECTROSPRAY-IONIZATION TO THE DETECTION OF DNA NUCLEOSIDES INANCIENT SEEDS

Liquid chromatography/mass spectrometry (LC/MS) with electrospray ioni zation has been used to analyse the nucleoside components of DNA extra cted from preserved plant remains. Optimum results were obtained by us e of an isocratic ammonium acetate/acetonitrile mobile phase with post -column addition of 50% v/v aqueous formic acid. Authentic DNA nucleos ides gave simple spectra displaying protonated molecular ions, [M+H](), and base ions, [BH2](+), carrying the bulk of the ion current. Sele cted ion monitoring (SIM) of these characteristic ions was employed to screen for the presence of deoxyribonucleosides in enzymatic hydrolys ates of DNA isolated from ancient seeds. This use of mass chromatograp hy with co-injection analyses confirmed the presence of 2'-deoxycytidi ne, 2'-deoxyadenosine and 2'-deoxyguanosine in 1400 year-old desiccate d radish (Raphanus sativus) and barley (Hordeum sp,) seeds. Detection of thymidine could not be confirmed due to a low response of this nucl eoside under the ionization conditions used. The use of LC/MS-SIM over comes problems of low volatility and co-eluting contaminants previousl y seen with GC/MS-SIM of DNA from ancient seeds.