Hoogsteen hydrogen bonds

Hoogsteen hydrogen bonding, 17 609, 610 Hooke s law, 21 719 Hookean region of stress—strain curve, 11 183, 184... 

J. Gu et al., A new insight into the structure and stability of hoogsteen hydrogen bonded g-tetrad an ab initio SCF study. Chem. Phys. Lett. 311, 209-214 (1999)... 

J. Gu, J. Leszczynski, A remarkable alteration in the bonding pattern An HF and DFT study of the interactions between the metal cations and the hoogsteen hydrogen-bonded G-tetrad. J. Phys. Chem. A 104, 6308-6313 (2000)... 

In agreement with the chemomimetic concept as defined by Eschen-moser, the panel of enzymatic transformations for the biosynthesis of purines that we currently observe in the cell can be hypothesized to have evolved from primitive chemical processes [48-50]. 2-Carbonitrile and 2-carboxamide AICA and AICN derivatives, respectively, were also used as intermediates for the synthesis of adenine 1 and 8-substituted adenines 7 and 8 [51]. In principle, purine derivatives 7 and 8 may pair with pyrimidine bases by formation of Watson-Crick or Hoogsteen hydrogen bond interactions. 

Figure 4 G-tetrad and G-quadruplexes. (A) Four guanine residues forming a planar structure G-tetrad through Hoogsteen hydrogen bonding. (B) A parallel G-quadruplex model. (C ) An intermolecular antiparallel G-quadruplex model. (D) An intramolecular basket G-quadruplex model. Each parallelogram in (B), (C), and (/>) represents a G-tetrad.

The chromosomes of eukaryotes are linear, and replication of the free ends of these linear DNA molecules presents particular problems. The sequencing of the ends of chromosomes revealed that they consist of telomeres, hundreds of tandem repeats of a hexanucleotide sequence, which in all vertebrates is d(TTAGGG). These G-rich telomeric sequences can fold into a G-quadruplex, a DNA secondary structure consisting of stacked G-tetrad planes, or G-quartets (Figure 9.18), connected by a network of Hoogsteen hydrogen bonds the cavity in the centre... 

Figure 17 A G-quartet formed from dG 11, a modified nucleobase with an expanded Hoogsteen hydrogen-bonding face. Note the additional hydrogen bonds, depicted by arrows, thought to be a reason for increased stability (See ref 31).

Jones and co-workers have used N7-labelled 2 -deoxyguanosine and 2 -deoxyadenosine incorporated into a synthetic oligonucleotide triplex stucture to study the hydrogen bonding at these sites. Hoogsteen hydrogen bonding to the N7 purine atoms was observed. ... 

The central strand of the triplex must be purine rich since a pyrimidine does not have two hydrogen bonding surfaces with more than one hydrogen bond. Thus triple-stranded DNA requires a homopurine homopyrimidine region of DNA. If the third strand is purine rich, it forms reverse Hoogsteen hydrogen bonds in an antiparallel orientation with the purine strand of the Watson-Crick helix. If the third strand is pyrimidine rich, it forms Hoogsteen bonds in a parallel orientation with the Watson-Crick paired purine strand. 

Figure 16 A combination of Watson-Crick and Hoogsteen hydrogen-bonding patterns permit the recognition between the adenine and the diimide.

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