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K A Kapitonova

Publications and source records attributed to K A Kapitonova.

5 recordsLinked to original sources
PubMed1983

Structure of the B DNA cationic shell as revealed by an X-ray diffraction study of CsDNA. Sequence-specific cationic stabilization of B form DNA.

Synchrotron radiation diffraction data for phage T2 CsDNA fibres have been used to determine the co-ordinates of the caesium ions in crystalline B form DNA. The R value is 0.16 for an optimized structure. The caesium ions are distributed equally between the narrow and wide grooves of B DNA and are located close to the dyad axes lying between the planes of adjacent base-pairs. On the wide-groove side the cations are separated from the nearest phosphate atoms by a hydration layer one to two water molecules thick. In the narrow groove the cations are directly co-ordinated to the base atoms and, for six out of ten possible DNA stacking types, form chelation complexes: O-2(Pyr)-Cs+-O-2(Pyr), O-2(Pyr)-Cs+-N-3(Pur) or N-3(Pur)-Cs+-N-3(Pur), which stabilize the B conformation. The steric properties of such complexes as estimated for different base sequences and for different ions are consistent with the structural behaviour of double-helical polynucleotides with different base sequences, as experimentally observed.

Cesium↗
PubMed1975

An x-ray diffraction study of ribosome structure.

Dense gels of E. coli 70 S ribosomes, their 50 S subunits, CM-like particles, RNP strands and their fragments, 38 S particles obtained from RNP strand folding upon addition of Mg2+ ions, and of unoriented salt-free and free rRNA sodium and magnesium salts were studied by X-ray diffraction. It was shown that under dense gel conditions RNA molecules contained in ribosomes unfolded by desalting, like all other particles considered here, have helical regions. Under these conditions free desalted RNA has no helical regions. Experimental data on X-ray scattering at medium angles were compared with the diffraction curves calculated for homogeneous prolate and oblate ellipsoids, for various ellipsoids containing a dense region or an internal cavity, and for ellipsoids containing internal periodic regions. The results indicate that the internal structure of the 50 S ribosome is periodic, i. e., its components form a periodic lattice. The lattice spacings are approximately 42 and 28 A with a 0.8g/g dry weight sample water content. When the 50 S particle water content drops below 0.2 g/g dry weight the periodic structure is disrupted. This disruption is reversible. It was shown that CM-like particles at high ionic strenght (2 M LiCl) have approximately the same internal periodicity as the 50 S particles, but in contrast they lose this periodicity at low ionic strength (10-2M tris-HCl and 5-10-3 M MgCl2).

Bacterial Proteins↗
PubMedDate not supplied

[Heavy cation position in the structure of the crystalline B-form of DNA].

Coordinates of caesium ions in DNA crystalline B-form were obtained by X-ray study of CsDNA with the use of synchrotron radiation. In conformity with the model that well meets the obtained set of structure factor amplitudes, the cations are located rather close to diad axes lying between the planes of successive nucleotide pairs. The cations in the narrow groove touch DNA surface, while those in the wide groove are rather far from the DNA molecule.

Cations↗