la5009939_si_003.mpg (2.08 MB)
Directing Assembly of DNA-Coated Colloids with Magnetic Fields To Generate Rigid, Semiflexible, and Flexible Chains
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posted on 2014-08-05, 00:00 authored by Julie Byrom, Patric Han, Michael Savory, Sibani Lisa BiswalWe report the formation of colloidal
macromolecules consisting
of chains of micron-sized paramagnetic particles assembled using a
magnetic field and linked with DNA. The interparticle spacing and
chain flexibility were controlled by varying the magnetic field strength
and the linker spring constant. Variations in the DNA lengths allowed
for the generation of chains with an improved range of flexibility
as compared to previous studies. These chains adopted the rigid-rod,
semiflexible, and flexible conformations that are characteristic of
linear polymer systems. These assembly techniques were investigated
to determine the effects of the nanoscale DNA linker properties on
the properties of the microscale colloidal chains. With stiff DNA
linkers (564 base pairs) the chains were only stable at moderate to
high field strengths and produced rigid chains. For flexible DNA linkers
(8000 base pairs), high magnetic field strengths caused the linkers
to be excluded from the gap between the particles, leading to a transition
from very flexible chains at low field strengths to semiflexible chains
at high field strengths. In the intermediate range of linker sizes,
the chains exhibited predictable behavior, demonstrating increased
flexibility with longer DNA linker length or smaller linking field
strengths. This study provides insight into the process of directed
assembly using magnetic fields and DNA by precisely tuning the components
to generate colloidal analogues of linear macromolecular chains.