jp8b10156_si_004.mpg (19.91 MB)
Tuning the Stability of DNA Nanotubes with Salt
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posted on 2019-03-19, 00:00 authored by Supriyo Naskar, Mounika Gosika, Himanshu Joshi, Prabal K. MaitiWe
report the enhancement of the structural stability of a DNA
nanotube (DNT) by changing the salt concentrations for three different
salt species, namely, NaCl, KCl, and MgCl2. Using fully
atomistic molecular dynamics simulations, we find that, with the gradual
increment in the NaCl salt concentration, the DNT becomes compact
and rigid. The significant reduction in the average root-mean-square
deviation, root-mean-square fluctuation, and effective radius of the
DNT with an increase in the NaCl concentration quantifies our observation.
We explain how the DNT–ion interactions play a vital role in
the conformational fluctuation of the DNT. To understand the salt
dependence of the mechanical properties of the DNTs, we have calculated
the stretch modulus (γ) and persistence length (LP) as a function of salt concentration. The calculated
stretch moduli of the DNTs change from 8.3 to 13 nN, and the persistence
length of the DNT varies from 6 to 10 μm when the NaCl salt
concentration is varied from 0 to 1 M. Both the stretch modulus and
the persistence length calculations reaffirm the structural stability
of the DNT at higher salt concentrations. We find similar trends for
another monovalent salt (KCl). However, for a divalent salt (MgCl2), we find minimal variation in the structural properties
with an increase in the salt concentration.