Fluorescence studies of polyriboadenylic acid and dinucleoside monophosphates containing 1,N6-ethenoadenosine

The fluorescence properties of the 1,N6-etheno derivatives of ApA (epsilon Ap epsilon A) and polyriboadenylic acid (poly epsilon rA) have been examined. The fluorescence quantum yield of poly epsilon rA decreases with an increase in the degree of epsilon-substitution and is much smaller than that for epsilon-AMP even for low degrees of epsilon-substitution. The nearest neighbor interactions such as adenine-epsilon-adenine and epsilon-adenine-epsilon-adenine may be responsible for this behavior. It is found that the fluorescence decay kinetics obeys a three-exponential decay law for poly epsilon rA and epsilon Ap epsilon A, suggesting that there exist at least three different stacked conformational states.