Inter-strand C-H...O hydrogen bonds stabilizing four-stranded intercalated molecules: stereoelectronic effects of O4' in cytosine-rich DNA.
AUTOR(ES)
Berger, I
RESUMO
DNA fragments with stretches of cytosine residues can fold into four-stranded structures in which two parallel duplexes, held together by hemiprotonated cytosine.cytosine+ (C.C+) base pairs, intercalate into each other with opposite polarity. The structural details of this intercalated DNA quadruplex have been assessed by solution NMR and single crystal x-ray diffraction studies of cytosine-rich sequences, including those present in metazoan telomeres. A conserved feature of these structures is the absence of stabilizing stacking interactions between the aromatic ring systems of adjacent C.C+ base pairs from intercalated duplexes. Effective stacking involves only the exocyclic keto groups and amino groups of the cytidine bases. The apparent absence of stability provided by stacking interactions between the bases in this intercalated DNA has prompted us to examine the available structures in detail, in particular with regard to unusual features that could compensate for the lack of base stacking. In addition to base-on-deoxyribose stacking and intra-cytidine C-H...O hydrogen bonds, this analysis reveals the presence of a hitherto unobserved, systematic intermolecular C-H...O hydrogen bonding network between the deoxyribose sugar moieties of antiparallel backbones in the four-stranded molecule.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=37952Documentos Relacionados
- Stable loop in the crystal structure of the intercalated four-stranded cytosine-rich metazoan telomere.
- Crystal structure of intercalated four-stranded d(C3T) at 1.4 A resolution.
- Identification of two human nuclear proteins that recognise the cytosine-rich strand of human telomeres in vitro
- Intramolecular folding of a fragment of the cytosine-rich strand of telomeric DNA into an i-motif.
- The bi-loop, a new general four-stranded DNA motif