10 research outputs found
Ionic liquids make DNA rigid
Persistence length of dsDNA is known to decrease with increase in ionic
concentration of the solution. In contrast to this, here we show that
persistence length of dsDNA increases dramatically as a function of ionic
liquid (IL) concentration. Using all atomic explicit solvent molecular dynamics
simulations and theoretical models we present, for the first time, a systematic
study to determine the mechanical properties of dsDNA in various hydrated ionic
liquids at different concentrations. We find that dsDNA in 50 wt% ILs have
lower persistence length and stretch modulus in comparison to 80 wt% ILs. We
further observe that both persistence length and stretch modulus of dsDNA
increase as we increase the ILs concentration. Present trend of stretch modulus
and persistence length of dsDNA with ILs concentration supports the predictions
of the macroscopic elastic theory, in contrast to the behavior exhibited by
dsDNA in monovalent salt. Our study further suggests the preferable ILs that
can be used for maintaining DNA stability during long-term storage.Comment: 16 pages, 3 figures, Supplementary Information (Accepted for
publication in the Journal of Chemical Physics, AIP (USA)
Dynamics of physiologically relevant noncanonical DNA structures: an overview from experimental and theoretical studies
DNA is a complex molecule with phenomenal inherent plasticity and the ability to form different hydrogen bonding patterns of varying stabilities. These properties enable DNA to attain a variety of structural and conformational polymorphic forms. Structurally, DNA can exist in single-stranded form or as higher-order structures, which include the canonical double helix as well as the noncanonical duplex, triplex and quadruplex species. Each of these structural forms in turn encompasses an ensemble of dynamically heterogeneous conformers depending on the sequence composition and environmental context. In vivo, the widely populated canonical B-DNA attains these noncanonical polymorphs during important cellular processes. While several investigations have focused on the structure of these noncanonical DNA, studying their dynamics has remained nontrivial. Here, we outline findings from some recent advanced experimental and molecular simulation techniques that have significantly contributed toward understanding the complex dynamics of physiologically relevant noncanonical forms of DNA
Nanostructural Reorganization Manifests in <i>Sui-Generis</i> Density Trend of Imidazolium Acetate/Water Binary Mixtures
Ionic liquids (ILs) are emerging
as a novel class of solvents in
chemical and biochemical research. Their range of applications further
expands when a small quantity of water is added. Thus, the past decade
has seen extensive research on IL/water binary mixtures. While the
thermophysical properties of most of these mixtures exhibited the
expected trend, few others have shown deviations from the general
course. One such example is the increase in density of the 1-alkyl-3-methyl
imidazolium acetate ([R<sub><i>n</i></sub>mim][Ac])-based
ILs with the addition of low to moderate concentrations of water.
Although such a unique trend was observed for imidazolium cations
of different tail lengths and also from independent experiments, the
molecular basis of this unique behavior remains unknown. In this study,
we examine the nanostructural reordering in [R<sub><i>n</i></sub>mim][Ac] (<i>n</i> = 2–6) ILs due to added
water by means of molecular dynamics simulations, and correlate the
observed changes to the <i>sui-generis</i> density trend.
Results suggest that the initial rise in density in these ILs mainly
pertains to the water-induced increased spatial correlation among
the polar components, where high basicity of the acetate anion plays
a key role. At moderate water concentration, the density can rise
further for ILs with longer cation tails due to hydrophobic clustering.
Thus, while [emim][Ac]/water mixtures exhibit the density turnover
at <i>X</i><sub>w</sub> = 0.5, [bmim][Ac] and [hmim][Ac]
show the turnover at <i>X</i><sub>w</sub> = 0.7. The detailed
understanding provided here could help the preparation of optimal
IL/water binary mixtures for various biochemical applications
Groove Binding Mechanism of Ionic Liquids: A Key Factor in Long-Term Stability of DNA in Hydrated Ionic Liquids?
Nucleic acid sample storage is of paramount importance
in biotechnology
and forensic sciences. Very recently, hydrated ionic liquids (ILs)
have been identified as ideal media for long-term DNA storage. Hence,
understanding the binding characteristics and molecular mechanism
of interactions of ILs with DNA is of both practical and fundamental
interest. Here, we employ molecular dynamics simulations and spectroscopic
experiments to unravel the key factors that stabilize DNA in hydrated
ILs. Both simulation and experimental results show that DNA maintains
the native B-conformation in ILs. Simulation results further suggest
that, apart from the electrostatic association of IL cations with
the DNA backbone, groove binding of IL cations through hydrophobic
and polar interactions contributes significantly to DNA stability.
Circular dichroism spectral measurements and fluorescent dye displacement
assay confirm the intrusion of IL molecules into the DNA minor groove.
Very interestingly, the IL ions were seen to disrupt the water cage
around DNA, including the spine of hydration in the minor groove.
This partial dehydration by ILs likely prevents the hydrolytic reactions
that denature DNA and helps stabilize DNA for the long term. The detailed
understanding of IL–DNA interactions provided here could guide
the future development of novel ILs, specific for nucleic acid solutes
Groove Binding Mechanism of Ionic Liquids: A Key Factor in Long-Term Stability of DNA in Hydrated Ionic Liquids?
Nucleic acid sample storage is of paramount importance
in biotechnology
and forensic sciences. Very recently, hydrated ionic liquids (ILs)
have been identified as ideal media for long-term DNA storage. Hence,
understanding the binding characteristics and molecular mechanism
of interactions of ILs with DNA is of both practical and fundamental
interest. Here, we employ molecular dynamics simulations and spectroscopic
experiments to unravel the key factors that stabilize DNA in hydrated
ILs. Both simulation and experimental results show that DNA maintains
the native B-conformation in ILs. Simulation results further suggest
that, apart from the electrostatic association of IL cations with
the DNA backbone, groove binding of IL cations through hydrophobic
and polar interactions contributes significantly to DNA stability.
Circular dichroism spectral measurements and fluorescent dye displacement
assay confirm the intrusion of IL molecules into the DNA minor groove.
Very interestingly, the IL ions were seen to disrupt the water cage
around DNA, including the spine of hydration in the minor groove.
This partial dehydration by ILs likely prevents the hydrolytic reactions
that denature DNA and helps stabilize DNA for the long term. The detailed
understanding of IL–DNA interactions provided here could guide
the future development of novel ILs, specific for nucleic acid solutes
High Nucleobase-Solubilizing Ability of Low-Viscous Ionic Liquid/Water Mixtures: Measurements and Mechanism
Research on nucleobases has always
been on the forefront owing
to their ever-increasing demand in the pharmaceutical, agricultural,
and other industries. The applications, however, became limited due
to their poor solubility in water. Recently, ionic liquids (ILs) have
emerged as promising solvents for nucleobase dissolution, as they
exhibit >100-fold increased solubility compared to water. But the
high viscosity of ILs remains as a bottleneck in the field. Here,
by solubility and viscosity measurements, we show that addition of
low-to-moderate quantity of water preserves the high solubilizing
capacity of ILs, while reducing the viscosity of the solution by several
folds. To understand the mechanism of nucleobase dissolution, molecular
dynamics simulations were carried out, which showed that at low concentrations
water incorporates into the IL–nucleobase network without much
perturbing of the nucleobase–IL interactions. At higher concentrations,
increasing numbers of IL anion–water hydrogen bonds replace
IL–nucleobase interactions, which have been confirmed by <sup>1</sup>H- and <sup>13</sup>C NMR chemical shifts of the IL ions