Anomalous Temperature Dependence of the Phosphorus-31 Nuclear Magnetic Resonance Chemical Shift in d(CCGG) and d(CCTAGG) at the Junction of the Pyrimidine Stack Followed by the Purine Stack

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Two self-complementary deoxyribo-oligonucleotides, d(CCGG) and d(CCTAGG), were synthesized. Their ^<31>P and ribose ^1H nuclear magnetic resonance (NMR) assignments were achieved by the use of ^<31>P-^1H and ^1H-^1H shift correlated two-dimensional NMR techniques in low salt solution. One of the phosphorus atoms in each of these two origomers showed an anomalous behavior : its resonance was shifted to lower field instead of higher field on lowering the temperature in the range below the melting temperature. This "anomalous" ^<31>P was assigned to CpG for d(CCGG), and TpA for d(CCTAGG). Among the four self-complementary G.C tetramers [d(CCGG), d(CGCG), d(GGCC), d(GCGC)], this anomalous behavior of ^<31>P was found only in d(CCGG)[D.J.Patel, Biopolymers, 15,533 (1976); ibid., 16,1635 (1977); ibid., 18,553 (1979)]. It was suggested from the results that a sequence 5'・・・(Py)p(Py)p(Pu)p(Pu)・・・3' always shows a conformational peculiarity at the (Py)p(Pu) portion, where Py=pyrimidine and Pu=purine nucleosides, and that the peculiarity involves the unusually low twist angle, t_g, (i.e.the local residual rotation around the helix axis).The anomalous ^<31>P behavior can be explained by postulating an intermediate form in the coil to helix transition.
社団法人日本薬学会の論文
1986-10-25