Recognition-mediated cucurbit[7]uril-heptamolybdate hybrid material: a facile supramolecular strategy for (99m)Tc separation.

We report the construction of a novel non-covalently held cucurbit[7]uril-heptamolybdate hybrid material for the first time, and demonstrate its application as a generator bed for the facile and efficient separation of the (99m)Tc radiotracer, which is in demand for several theranostic applications.

Thermodynamics and solvation dynamics of BIV TAR RNA-Tat peptide interaction.

The interaction of the trans-activation responsive (TAR) region of bovine immunodeficiency virus (BIV) RNA with the Tat peptide is known to play important role in viral replication. Despite being thoroughly studied through a structural point of view, the nature of binding between BIV TAR RNA and the BIV Tat peptide requires information related to its thermodynamics and the nature of hydration around the TAR-Tat complex. In this context, we carried out the thermodynamic study of binding of the Tat peptide to the BIV TAR RNA hairpin through different calorimetric and spectroscopic measurements.

Effect of ionic size on the structure of cylindrical electric double layers: a systematic study by Monte Carlo simulations and density functional theory.

The effect of ionic size on the diffuse layer characteristics of a cylindrical electric double layer is studied using density functional theory and Monte Carlo simulations for the restricted primitive model and solvent primitive model. The double layer is comprised of an infinitely long, rigid, impenetrable charged cylinder also referred to as the polyion, located at the center of a cylindrical cell containing the electrolyte, which is composed of charged hard spheres and the solvent molecules as neutral hard spheres (in the case of the solvent primitive model). The diameters of all the hard spheres are taken to be the same.

Fluorescence dynamics of double- and single-stranded DNA bound to histone and micellar surfaces.

The study of structure and dynamics of bound DNA has special implications in the context of its biological as well as material functions. It is of fundamental importance to understand how a binding surface affects different positions of DNA with respect to its open ends. Because double-stranded (ds) and single-stranded (ss) DNA are the predominant functional forms, we studied the site-specific dynamics of these DNA forms, bound to the oppositely charged surface of histones, and compared the effects with that of DNA bound to cetyltrimethyl ammonium bromide micelles.

Three component model of cylindrical electric double layers containing mixed electrolytes: A systematic study by Monte Carlo simulations and density functional theory.

The structure of electric double layer around a hard rigid impenetrable cylindrical polyion is studied using density functional theory as well as Monte Carlo simulations. The three component model, presented here, is an extension of solvent primitive model where the solvent molecules are treated as the neutral hard spheres, counterions and coions as the charged hard spheres, all of equal diameters, and in addition the mixture of mono- and multivalent counterions are also considered. The theory is partially perturbative where the hard sphere interactions are treated within the weighted density approach and the corresponding ionic interactions have been evaluated through second-order functional Taylor expansion with respect to the bulk electrolyte.

Excess entropy scaling of transport properties of Lennard-Jones chains.

Excess-entropy scaling relationships for diffusivity and viscosity of Lennard-Jones chain fluids are tested using molecular dynamics simulations for chain sizes that are sufficiently small that chain entanglement effects are insignificant. The thermodynamic excess entropy S(e) is estimated using self-associating fluid theory (SAFT). A structural measure of the entropy S(2) is also computed from the monomer-monomer pair correlation function, g(m)(r).

Structure of cylindrical electric double layers: a systematic study by Monte Carlo simulations and density functional theory.

We present a systematic study of the structure of cylindrical double layers to envisage the distribution of small ions around a cylindrical polyion through canonical Monte Carlo simulation and density functional theory. The polyion is modeled as an infinite, rigid, and impenetrable charged cylinder surrounded by charged hard spheres of equal diameter modeled for small ions of the electrolyte. The solvent is considered as dielectric continuum.

Molecular solvent model of cylindrical electric double layers: a systematic study by Monte Carlo simulations and density functional theory.

We present the Monte Carlo simulation and density functional study of structure of cylindrical double layers considering solvent as the third component. We have chosen molecular solvent model, where ions and solvent molecules are considered as charged and neutral hard spheres, respectively, having equal diameter. The polyionic cylinder is modeled as an infinite, rigid, and impenetrable charged hard cylinder surrounded by the electrolyte and the solvent spheres.

Structure of spherical electric double layers: a density functional approach.

A density functional theory is presented for the structure of spherical electric double layers within the restricted primitive model, where the macroion is considered as a hard sphere having uniform surface charge density, the small ions as charged hard spheres, and the solvent is taken as a dielectric continuum. The theory is partially perturbative as the hard-sphere contribution to the one-particle correlation function is evaluated using suitably averaged weighted density and the ionic part is obtained through a second-order functional Taylor expansion around the uniform fluid. The theory is in quantitative agreement with Monte Carlo simulation for the density profiles and the zeta potentials over a wide range of macroion sizes and electrolyte concentrations.

Microenvironment in the corona region of triblock copolymer micelles: temperature dependent solvation and rotational relaxation dynamics of coumarin dyes.

Dynamic Stokes' shift and fluorescence anisotropy measurements using coumarin-153 (C153) and coumarin-151 (C151) as the fluorescence probes have been carried out in aqueous poly(ethylene oxide)20-poly(propylene oxide)70-poly(ethylene oxide)20 (P123) and poly(ethylene oxide)100-poly(propylene oxide)70-poly(ethylene oxide)100 (F127) block copolymer micelles with an aim to understand the water structures and dynamics in the micellar corona region. It has been established that the probes reside in the micellar corona region. It is indicated that the corona regions of P123 and F127 micelles are relatively less hydrated than the Palisade layers of neutral micelles like Triton-X-100 and Brij-35.

Effect of lithium chloride on the palisade layer of the Triton-X-100 micelle: two sites for lithium ions as revealed by solvation and rotational dynamics studies.

Dynamic Stokes' shift measurements using coumarin 153 as the fluorescence probe have been carried out to explore the effect of added electrolyte, lithium chloride (LiCl), on solvation dynamics in the Triton-X-100 (TX-100) micelle and thus to understand the changes in micellar Palisade layer, especially the entrapped water structures in the Palisade layer. At all concentrations of LiCl, the spectral shift correlation function shows biexponential decay. At lower LiCl concentrations, the longer solvation time is seen to decrease, although the shorter solvation time is not affected much.

Nature of the water molecules in the palisade layer of a triton X-100 micelle in the presence of added salts: A solvation dynamics study.

The effect of added electrolytes on the nature of water molecules in the palisade layer of a Triton X-100 (TX-100) micelle has been investigated using solvation dynamics studies of C153 dye in the presence of different concentrations of NaCl, KCl, and CsCl salts. In all of the cases, the solvation dynamics is found to be biexponential in nature. It is seen that in the presence of added salts the solvation dynamics becomes slower.

Effect of attractive interactions on the structure of polymer melts confined between surfaces: a density-functional approach.

A density-functional theory is presented to study the structure of polymers, having attractive interactions, confined between attractive surfaces. The theory treats the ideal-gas free-energy functional exactly and uses weighted density approximation for the hard-chain contribution to the excess free-energy functional. The bulk interactions of freely jointed hard spheres are obtained from generalized Flory equation of state and the attractive interactions are calculated using the direct correlation function obtained from the polymer reference interaction site model theory along with the mean spherical approximation closure.

Structure of short polymers at interfaces: a combined simulation and theoretical study.

The structure of polymers confined between surfaces is studied using computer simulation and a density functional approach. The simple model system considers the polymer molecule as a pearl necklace of freely jointed hard spheres, having attractions among the beads, confined between attractive surfaces. This approach uses the universality of the free-energy functional to obtain the self-consistent field required in the single chain simulation.