Nanoscale Structure and Interaction of Condensed Phases of DNA–Carbon
Nanotube Hybrids
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Abstract
Condensation of DNA–carbon
nanotube (CNT) hybrids dispersed in aqueous solutions can be induced
by elevated hybrid concentrations, salts, or crowding agents. DNA–CNT
condensates exhibit either nematic ordering or amorphous aggregates,
dependent on the nature of interhybrid interactions. This study employed
X-ray diffraction (XRD) to determine nanoscale structures of the condensates,
including the presence of positional ordering, interaxial distances,
and the range of ordered domains. To probe the effects of DNA sequence,
two types of CNT hybrids, dispersed by genomic DNA of random sequence
and synthetic oligonucleotides respectively, were studied under identical
conditions. The osmotic stress method was further used to quantify
force–distance dependencies of the DNA–CNT hybrids to
elucidate the relation between interhybrid interactions and condensate
structures. We observed that, independent of DNA sequence, lyotropic
DNA–CNT phases showed weak positional ordering with long interhybrid
distances, salt-induced condensates were amorphous, crowding-condensed
DNA–CNTs were the most ordered with pronounced XRD peaks, and
interhybrid interactions were defined by short-range hydration repulsion
and long-range electrostatic repulsion. Conversely, the effects of
DNA sequence became evident as to their quantitative force–distance
relationships. Genomic DNA of random sequence consistently gave longer
interhybrid distances than synthetic oligonucleotides, which we attribute
to the likely differences in their hybrid diameters