Terminal Sequence-Specific Interparticle Attraction
between DNA Duplex-Carrying Polystyrene Microparticles in Aqueous
Salt Solution Assessed by Optical Tweezers
posted on 2021-04-19, 15:33authored byHiroya Nakauchi, Mizuo Maeda, Naoki Kanayama
The dispersion behavior of DNA duplex-carrying
colloidal particles
in aqueous high-salt solutions shows extraordinary selectivity against
the duplex terminal sequence. We investigated the interparticle force
between DNA duplex-carrying polystyrene (dsDNA-PS) microparticles
in aqueous salt solutions and examined their behavior in relation
to the duplex terminal sequences. Force–distance (F–D) curves for a pair of dsDNA-PS particles were recorded with a dual-beam
optical tweezers system with the two optically trapped particles closely
approaching each other. Interestingly, only 3–5% of the oligo-DNA
strands on the dsDNA-PS particles formed a duplex with complementary
DNAs, and the F–D curves showed a distinct
specificity to the duplex terminal sequences in the interparticle
force at a high-NaCl concentration; a clear attraction peak was observed
in F–D curves only when the duplex terminal
was a complementary base pair. The attractive strength reached 2.6
± 0.5 pN at 500 mM NaCl and 4.3 ± 1.0 pN at 750 mM NaCl.
By sharp contrast, no significant attraction occurred for the particles
with mismatched duplex terminals even at 750 mM NaCl. Similar duplex
terminal-specificity in the interparticle force was also confirmed
for dsDNA-PS particles in divalent MgCl2 solutions. Considering
that the duplex terminal sequences on the dsDNA-PS particles showed
only a negligible difference in their surface charges under identical
salt conditions, we concluded that the interparticle attraction observed
only for the dsDNA-PS particles with complementary duplex terminals
is attributable to the salt-facilitated stacking interaction between
the paired terminal nucleobases (i.e., blunt-end stacking) on the
dsDNA-PS surfaces. Our results thus demonstrate the occurrence of
a duplex terminal-specific interparticle force between dsDNA-PS particles
under high-salt conditions.