Structure of poly (dT).poly (dA).poly (dT) |
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Authors: | Chandrasekaran R Giacometti A Arnott S |
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Institution: | Whistler Center for Carbohydrate Research, Purdue University, West Lafayette, IN 47907, USA. chandra@purdue.edu |
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Abstract: | The molecular structure of poly (dT).poly (dA).poly (dT) has been determined and refined using the continuous x-ray intensity data on layer lines in the diffraction pattern obtained from an oriented fiber of the DNA. The final R-value for the preferred structure is 0.29 significantly lower than that for plausible alternatives. The molecule forms a 12-fold right-handed triple-helix of pitch 38.4 A and each base triplet is stabilized by a set of four Crick-Watson-Hoogsteen hydrogen bonds. The deoxyribose rings in all the three strands have C2'-endo conformations. The grooveless cylindrical shape of the triple-helix is consistent with the lack of lateral organization in the fiber. |
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