A calorimetric investigation of tRNA1Val melting

Calorimetric Investigations on Thermal Stability of tRNAIle (Yeast) and tRNASer (Yeast)

“…, the value previously reported for tRNAVa' [14]. However, the situation changes drastically on increasing magnesium ion activity in solution.…”

“…It has been already reported [14,17] that the stability of the base line position permits evaluation of values for partial heat capacities from scanning calorimetry experiments. The mean value of the partial specific heat capacity, c;, at 20 "C for tRNA"" in the presence of Mg2+ was found to be equal to 0.26 f 0.04cal.K-' .g-'(1.09 f 0 .…”

“…tRNA!le contained 5 % of tRNA::' and 3% of tRNA?;"'. Assuming molecular weights of 27700 and 25000 for tRNASer (yeast) and tRNA"" (yeast), respectively [14,15] absorption coefficients for 0.1 % solutions at 260 nm (1 cm optical path length) have been calculated on the basis of the acceptor activity :…”

“…To provide a basis for comparison of melting curves of tRNA"" and tRNASe' with previously published results on tRNAVal, largely the same conditions were adopted [14]. Except for a few experiments, when sodium citrate was employed to examine the influence of the buffer on the thermodynamic transition parameters, all solutions contained 5 mM NaHZPOd/NaOH, pH 7.0.…”

“…In view of the conflicting evidence with regard to thermodynamic parameters reported for the transition of native to reversibly denatured tRNA , an extensive study employing tRNA"' and tRNAS" from yeast under various solution conditions was performed. These tRNA's are representative species of the two classes of transfer ribonucleic acids, since tRNAS" (yeast) consists of 85 nucleotides [14] exhibiting a pronounced extra loop in the cloverleaf arrangement, whereas tRNA"" supposedly resembles Therrnophilus utilis tRNA1Ie [15] with a small extra loop; however, the exact sequence of tRNA"' (yeast) is still unknown.…”