Mass spectral studies of probe pyrolysis products of intact oligoribonucleotides.

Pyrolysis of underivatized homogeneous oligoribonucleotides in the source of a mass spectrometer leads to production of simple mass spectra which resemble the spectra of the bases themselves. It is proposed that pyrolysis occurs by hydrogen transfer to the base moiety followed by elimination of the neutral base. Ionization by electron impact gives rise to the observed spectra. Mixed oligoribonucleotides pyrolyze readily to give spectra of adenine and uracil, but evidence for the presence of guanine and cytosine in mixed polymers and native RNA's is difficult to obtain presumably because of their low vapor pressure. The method may be useful for detection of modified bases in tRNA and for studies of temperature effects on RNA pyrolysis.