Calorimetric Studies on Melting of tRNAPhe (Yeast)

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Abstract
The heat effects involved in thermal unfolding of tRNAPhe [phenylalanine-labelled transfer RNA] from yeast were determined in various buffer systems by direct differential scanning calorimetry. Perfect reversibility of the melting process was demonstrated for measurements in the absence of Mg2+ ions. The overall molar transition enthalpy, .DELTA.Ht = 298 .+-. 15 kcal/mol (1247 .+-. 63 kJ/mol), was independent of the NaCl concentration and the nature of the buffers used. .DELTA.Ht was identical in the presence or absence of Mg2+ ions within the margin of experimental error. A vanishing or very small heat capacity change may be associated with melting. Decomposition of the calorimetrically determined complex transition curves, on the assumption that the experimental melting profile represents the sum of independent 2-state transitions, resulted in 5 transitions which were assigned to melting of different structural domains of the tRNA.