Intensity fluctuation on spectroscopy and transfer RNA conformation: I. Melting Curves

Abstract Time-dependent correlation functions of tRNA from baker's yeast in 0.01 M Tris · HCl, 0.2 M NaCl, 0.001 M EDTA at pH 6.9, 5.8, and 4.8 were measured by means of a 96-channel single-clipped digital photon correlation spectrometer over a range of temperatures varying from 25 to 90°C. The data could be fitted using a single exponential decay time indicating a high degree of uniformity in size and shape for our tRNA solutions at each temperature and concentration studied. We were able to observe at least three distinguishable steps in the melting process for each solution of different pH values. For the solution of neutral pH, the relative translational diffusion coefficient increases with temperature from about 25 to 35°C before the usual decrease with increasing temperatures. The presence of this intermediate structure was also suggested independently from recent NMR measurements for yeast tRNA Gly .