Download DNA TRIPLEX Triplex structures are characterized by a single

DNA TRIPLEX
Triplex structures are characterized by a single polynucleotide strand residing in the former major
groove of a homopurine-homopyrimidine duplex , which are reviewed in Chapter 1 of this book. Two
triplex motifs are known. The parallel- or pyrimidine-motif (Py) has a C- or T-rich third strand bound
in a parallel orientation with respect to the duplex homopurine strand, while the antiparallel- or
purine-motif (Pu) has the opposite orientation and a primarily A- or G-rich third strand. Both types of
triplexes utilize Hoogsteen hydrogen bonding between their third strands and purines in their duplex
acceptors. The primary base triplets of Py triplexes are T•A•T and C•G•C+, while the base triplets of
Pu triplexes are T•A•A, T•A•T, and C•G•G . Py triplexes can occur with RNA being present as any of
the three strands, while Pu triplexes only occur with DNA
DNA QUADRUPLEXES
DNAs (and RNAs) containing guanine tracts will associate in vitro to form four-stranded, righthanded helices known as plexes or tetraplexes. G4 nucleic acids are characterized by stacked Gquartet structures, square planar arrays of four guanines, each serving as the donor and acceptor of
two Hoogsteen hydrogen bonds. Electronegative carbonyl oxygens line the center of the G-ring,
where they interact with a suitably sized monovalent cation, typically Na+ or K+ .
ROLE OF DNA HELICES AND QUADRAPLEXES IN TRANSCRIPTION
Please visit the following sites:
1.link.springer.com/chapter/10.1007%2F0-387-29148-2_8
2.https://books.google.co.in/books?isbn=0387291482
TRIPLE HELIX-INTERACTING PROTEINS AND CANCER
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