Interaction of (2? -5?) and (3? -5?) Linked 2-Aminoadenylyl-3-aminoadenosines with Polyuridylic Acid

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Abstract
2′-5′ and 3′-5′ linked 2-aminoadenylyl-2-aminoadenosines [(2′-5′)n2Apn2A (1) and (3′-5′)n2Apn2A (2)] were synthesized by condensation of 5′-O-monomethoxytrityl-N 2 N 6-dibenzoyl-2-aminoadenosine and N 2,N 6,2′,3′-O-tetrabenzoyl-2-aminoadenosine 5′-phosphate using dicyclohexylcarbodiimide (DCC). The conformational properties of these dimers 1 and 2 were examined by UV, NMR and CD spectroscopy. The results reveal that the 2′-5′-isomer 1 takes a stacked conformation, which contains a larger base-base overlap and is more stable against thermal perturbation with respect to the 3′-5′-isomer 2. Interactions of 1 and 2 with polyuridylic acid (Poly (U)) were also examined by Tm, mixing curves, UV and CD spectra. Both the dinucleoside isomers 1 and 2 formed a complex of 1 : 2 stoichiometry with poly(U), which was much more stable than that of the corresponding ApA isomer