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1H‐ and 31P‐nuclear magnetic resonance studies on the conformation of d‐(CpGpCpG)2 and d‐(CpGpCpGpCpG)2 short helices in B‐conformation

Two short DNA helices, d‐(CpGpCpG)2 and d‐(CpGpCpGpCpG)2, in dilute salt solutions have been studied thoroughly by 1H‐ and 31P‐nmr spectroscopy as model systems for the calibration of nmr theory in its application to nucleic acids research. All the nonexchangeable proton resonances of these two short helices have been assigned by the “incremental method,” “sequential homodecoupling” of the sugar protons, thermal perturbation, and computer spectral simulation, as well as the NOE technique.