Here we further comment on the role that the central cations play in G-quadruplex systems consisting planar disclike G-quartets.
Close inspection of the acidic 5'-GMP helix suggests that the formation of this strong [N.sub.2]-Hb ***O=P hydrogen bond causes a tilting of the guanine base, thus making it more difficult to form a planar disclike [G.sub.4].
Nectar secreted in alternistaminal troughs on staminal tube or staminal feet or from disclike nectary around base of ovary, more rarely from sides of ovary or absent.
n = 3 representing the formation of spherulite crystal, n = 2 representing the formation of the disclike crystal, and n = 1 representing the formation of rod-like crystal.