DETECTION OF NUCLEOTIDE BASES IN ANCIENT SEEDS USING GAS-CHROMATOGRAPHY MASS-SPECTROMETRY AND GAS-CHROMATOGRAPHY MASS-SPECTROMETRY MASS-SPECTROMETRY

Nucleic acid extracts from 1400-year-old radish seeds recovered from e xcavations at Qasr Ibrim, Upper Egypt, have been analysed by gas chrom atography/mass spectrometry and gas chromatography/mass spectrometry/m ass spectrometry. tert-Butyldimethylsilyl derivatives of the purine an d pyrimidine bases were prepared, after treatment of the nucleic acid extracts with concentrated formic acid. Under electron ionization thes e derivatives yield prominent [M-57]+ ions that were found to be of va lue for use in analyses employing selected-ion monitoring and product- ion studies. These two techniques were used in the sensitive and selec tive detection of nucleotide bases in crude extracts of ancient seeds. The results obtained were supported by complementary analyses of hydr olysates of ancient nucleic acids and authentic bases by means of rete ntion time and spectral comparisons. This work demonstrates for the fi rst time that mass spectrometry can be used in the direct chemical exa mination of nucleotide bases in ancient materials. This analytical app roach is currently being used to address questions regarding the possi ble chemical (diagenetic) changes occurring in the nucleic acids of an cient biological material.