Intrinsic emission properties of trinucleotides at 293 and 77 K.

The intrinsic emission properties of two pairs of isomeric trinucleotides, ApCpGp-CpApGp and ApUpGp-UpApGp, in neutral pH solvent between 293 and 77 K were studied. On the basis of the results obtained upon their emission spectroscopy, the fluorescence of these trinucleotides both at 293 and 77K can be regarded as the intramolecular excimer fluorescence which is red-shifted and broadened compared with that of corresponding equimolar mixture of constituent mononucleotides. On the other hand, the phosphorescence of two pairs of isomers observed at 77K is a characteristic of adenine. Thus, it is assumed that in above trinucleotides, the electronic excitation energy transfer takes place via the excimer state to the lowest triplet state of adenine.