Abstract
The influence of pH on an equimolar mixture of poly (A) and poly (U) in 0.1mol dm-3 acetate buffer solution was studied by means of heat of mixing and CD spectra.
The heat of mixing, ΔHM, in the region where pH is less than 5.5 is nearly zero, suggesting that in acidic solution an equimolar mixture of poly (A) and poly (U) may be due to result in the interaction between poly (A)·poly (A) duplex and poly (U) as pointed out by CD spectral measurement.
On the other hand, in less acidic solution where pH is more than 5.5 an equimolar mixture of poly (A) and poly (U) leads to poly (A)·poly (U) duplex formed by the interaction between poly (A) and poly (U) and its enthalpy change is estimated to be about -17.6±2.1kJ per mole of base pair of nucleotide.
Calorimetric studies of acidic and less acidic solutions seem to reflect exactly the results of the CD spectral measurements.
