TY - JOUR
T1 - Structure of poly d(ai)·poly d(ct) in two different packing arrangements
AU - Chandrasekaran, Rengaswami
AU - Radha, Akella
AU - Park, Hye Shin
N1 - Funding Information:
This work was supported in part by the National Institutes of Health and the Industrial Consortium of the Whistler Center for Carbohydrate Research.
PY - 1997/10
Y1 - 1997/10
N2 - X-ray diffraction analysis of poly d(AI)poly·d(CT) in oriented and polycrystalline fibers has revealed the DNA structure to be a 10-fold, right-handed, antiparallel, Watson-Crick base paired double helix in two distinct packing arrangements corresponding to one and two helices, respectively, in the unit cell. The helix pitch is 32.1 Å and 32.4 Å in the two cases, almost 1.5 Å shorter than in classical B-DNA. The resulting B-DNA geometry, described in terms of a tetranucleotide repeat which is conformationally similar to B-DNA, has its minor groove closely shut and major groove correspondingly widened, thus striking a sharp morphological contrast to B-DNA. According to difference electron density maps, a spine of hydration along the minor groove connects both strands and provides structural stability; ordered sodium ions and water molecules are actively involved in bridging the phosphate groups of neighboring helices. The crystallographic R-values for these two allomorphs are 0.26 and 0.20, respectively, for data up to 3. 0 Å resolution.
AB - X-ray diffraction analysis of poly d(AI)poly·d(CT) in oriented and polycrystalline fibers has revealed the DNA structure to be a 10-fold, right-handed, antiparallel, Watson-Crick base paired double helix in two distinct packing arrangements corresponding to one and two helices, respectively, in the unit cell. The helix pitch is 32.1 Å and 32.4 Å in the two cases, almost 1.5 Å shorter than in classical B-DNA. The resulting B-DNA geometry, described in terms of a tetranucleotide repeat which is conformationally similar to B-DNA, has its minor groove closely shut and major groove correspondingly widened, thus striking a sharp morphological contrast to B-DNA. According to difference electron density maps, a spine of hydration along the minor groove connects both strands and provides structural stability; ordered sodium ions and water molecules are actively involved in bridging the phosphate groups of neighboring helices. The crystallographic R-values for these two allomorphs are 0.26 and 0.20, respectively, for data up to 3. 0 Å resolution.
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U2 - 10.1080/07391102.1997.10508193
DO - 10.1080/07391102.1997.10508193
M3 - Article
C2 - 9399156
AN - SCOPUS:0030815280
SN - 0739-1102
VL - 15
SP - 285
EP - 305
JO - Journal of Biomolecular Structure and Dynamics
JF - Journal of Biomolecular Structure and Dynamics
IS - 2
ER -