Chemistry Reference
In-Depth Information
their biological implications, the propensity for G-quadruplexes to form cation-
specifi c supramolecular structures has opened the possibility for using guanine
nucleoside and nucleotide analogues as well as G-rich DNA sequences for applica-
tions that range from environmental remediation to organic synthesis and nanote-
chnology.
55 - 69
For example, molecular self-assembly of guanine-containing nucleosides
has been shown to be useful for the construction of highly selective ionophores.
70,71
G-rich sequences that fold into G-quadruplex structures can, of course, form
Watson-Crick duplexes with their complementary C-rich strands. The formation of
G-quadruplex or duplex structures within the cell will therefore depend on the rela-
tive stability of the G-quadruplex and the corresponding duplex.
72 - 78
Furthermore,
the C-rich strand might have the possibility of forming an intramolecular i-motif
that likewise competes with duplex formation, which can also be infl uenced by
cations or other changes in solution conditions (e.g. molecular crowding).
79 - 83
The basic building block of a G-quadruplex is the G•G•G•G quartet, which is
composed of four hydrogen-bonded guanine nucleotides in a horizontal planar
arrangement (Figure 3.1). G-quartets are linked together by eight hydrogen bonds
Figure 3.1
The G-quartet: (a) four guanine residues that act both as acceptors and donors
of H-bonds in Hoogsteen geometry form a cyclic G-quartet. R represents 2
-deoxyribose
moiety; (b) side view of this planar building block of G-quadruplexes in cartoon
presentation
′
