Liquid crystal ordering
is reported in aqueous solutions of the
oligomer 5′-ATTAp-3′ and of the oligomer 5′-GCCGp-3′.
In both systems, we quantitatively interpret ordering as stemming
from the chaining of molecules <i>via</i> a “running-bond”
type of pairing, a self-assembly process distinct from the duplex
aggregation previously reported for longer oligonucleotides. While
concentrated solutions of 5′-ATTAp-3′ show only a columnar
liquid crystal phase, solutions of 5′-GCCGp-3′ display
a rich phase diagram, featuring a chiral nematic phase analogous to
those observed in solutions of longer oligonucleotides and two unconventional
phases, a columnar crystal and, at high concentration, an isotropic
amorphous gel. The appearance of these phases, which can be interpreted
on the basis of features of 5′-GCCGp-3′molecular structure,
suggests distinctive assembly motifs specific to ultrashort oligonucleotides
