Infrared spectra of transfer RNA's: II. Formylmethionine transfer RNA from Escherichia coli in aqueous solution

Abstract

Infrared absorption spectrum has been observed in the 1450–1750 cm −1 region of formylmethionine transfer RNA (tRNA) from Escherichia coli in deuterium oxide solution with 0.2 M Na + or 0.005 M Mg 2+. At 33°, the spectrum shows seven absorption peaks in the spectral region in question. On the basis of the positions and relative intensities of these peaks, the amounts of the adenine-uracil (AU) base pair, guanine-cytosine (GC) base pair, free adenine, uracil, guanine and cytosine residues are estimated. A calculated spectrum of 2 AU+17 GC+13 A+6 U+7 G+8 C (which corresponds to the “clover leaf” arrangement of the nucleotide sequence of this tRNA determined by Dube et al. 11,12, is in agreement with the observed spectrum. On heating the solutions, marked changes are observed in the positions and intensities of the absorption peaks. These changes are explained as what are caused by breaking down the AU and GC hydrogen-bonded base pairs. The amounts of the remaining base pairs are estimated at each temperature.