THERMODYNAMIC PROPERTIES OF 3 CONFORMATIONAL TRANSITIONS OF ALANINE SPECIFIC TRANSFER RNA FROM YEAST

The melting behavior of alanine specific tRNA was studied by a modified differential absorption technique. It was found that the melting proceeds in three resolvable steps, 1, 2, 3. Steps 1 and 3 were interpreted as single processes, step 2 as two superimposed transitions. The corresponding reaction enthalpies were determined to be ΔH (1) = 40 ± 10, ΔH (2) = 2 · (65 ± 10) and ΔH (3) = 70 ± 10 kcal/mole, and are discussed on the basis of the clover-leaf" model. Only the ionic strength dependence of steps 2 and 3 agrees with other double-stranded nucleic acids. Step 1 produces a smaller change in sedimentation coefficient than step 2. © 1969."