Nanotubes can selectively conduct ions across membranes to make ionic devices with transport characteristics similar biological ion channels and semiconductor electron devices. Depending on the surface charge profile of nanopore, ohmic resistors, rectifiers, diodes be made. Here we show that a uniformly charged conical nanopore have all these properties by changing species their concentrations each side membrane. Moreover, cation versus anion selectivity pores changed. We find polyvalent...

Generally, the parameters in interaction potential between like molecules a mixture can be determined relatively straightforward manner from properties of pure components. However, determination unlike pairs mixtures is more difficult. As result, these are usually estimated averages parameters. The most common recipes Lorentz–Berthelot mixing rules, where energy and molecular size presumed to geometric arithmetic averages, respectively. There have been some studies consequences deviations...

Despite the fact that our conceptual understanding of electrical double layer has advanced during past few decades, interpretation experimental and applied work is still largely based on venerable Poisson–Boltzmann theory Gouy, Chapman Stern. This understandable since this simple analytic. However, it not very accurate because atomic/molecular nature ions/solvent their correlations are ignored. Simulation some theoretical studies by ourselves others have discussed. These show GCS predicts a...

The efficient calculation of induced charges in an inhomogeneous dielectric is important simulations and coarse-grained models molecular biology, chemical physics, electrochemistry. We present the charge computation (ICC) method for polarization based on variational formulation Allen et al. [Phys. Chem. Phys. 3, 4177 (2001)]. give a different solution their extremum condition that produces matrix formulation. are directly calculated by solving linear equation Ah=c, where h contains...

Monte Carlo (MC) and density functional theory (DFT) results are reported for an electrolyte, consisting of charged hard spheres diameter 3 Å with the solvent modeled as a dielectric continuum, near flat uniformly electrode. These more interesting than earlier MC Torrie Valleau [J. Chem. Phys. 73, 5807 (1980); J. 86, 3251 (1982)] 4.25 because popular Gouy–Chapman (GC) is less successful this system. The DFT in good agreement results. Both show particularly features when counterions divalent....

Canonical Monte Carlo simulations were performed for a nonprimitive model of an electrical double layer. The ions and the solvent molecules are modeled as charged dipolar hard spheres, respectively, while electrode hard, impenetrable wall carrying uniform surface charge. We found that ion-dipole gives reasonable description layer partially with small to moderate dipole moments, or equivalently “effective” dielectric constant. Density, polarization mean electrostatic potential profiles...

A physical model of selective “ion binding” in the L-type calcium channel is constructed, and consequences are compared with experimental data. This reduced treats only ions carboxylate oxygens EEEE locus explicitly restricts interactions to hard-core repulsion ion–ion ion–dielectric electrostatic forces. The structural atoms provide a flexible environment for passing cations, thus resulting self-organized induced-fit selectivity filter. Experimental conditions involving binary mixtures...

We propose a simple model to explain the nonmonotonic concentration dependence of mean activity coefficient electrolytes without using any adjustable parameters. The primitive is used describe interaction between ions computed by adaptive grand canonical Monte Carlo method. For dielectric constant electrolyte, we use experimental dependent values. This included through solvation term in our treatment and water that changes as with concentration. Born-treatment fitted hydration energies. Our...

A mechanism for selectivity of calcium over sodium in a biological channel is studied by means Monte Carlo simulation. This model an infinite cylinder containing negatively charged glutamates, each modeled as pair half oxygens, and electrolyte. The fluid the equilibrium with bulk proportion Ca2+ ions greatly excess that because, restricted space channel, doubly require less volume are more effective at neutralizing charge glutamates than twice number singly Na+ same amount charge.

Monte Carlo simulations are reported for charged hard spheres at high density near a wall. This system is simple model molten salt double layer. Unfortunately, the reduced temperatures that correspond to experiment very small. results in large Boltzmann factor. As result, we unable obtain meaningful such low values and report only moderately of temperature. Even so, our should be useful benchmark. Further, able give qualitative answer an interesting question. We find capacitance point zero...

Density functional theory (DFT) of electrolytes is applied to the electrical double layer under a wide range conditions. The ions are charged, hard spheres different size and valence, wall creating uncharged, weakly strongly charged. Under all conditions, density electrostatic potential profiles calculated using recently proposed RFD (Gillespie et al 2002 J. Phys.: Condens. Matter 14 12129; 2003 Phys. Rev. E 68 031503) compare well Monte Carlo simulations. When results agree with simpler...

Calcium-selective ion channels are known to have carboxylate-rich selectivity filters, a common motif that is primarily responsible for their high Ca2+ affinity. Different affinities ranging from micromolar (the L-type Ca channel) millimolar ryanodine receptor closely related the different physiological functions of these channels. To understand physical mechanism this range given similar amino acids in we use grand canonical Monte Carlo simulations assess binding monovalent and divalent...

Monte Carlo simulation and density functional theoretical (DFT) results are reported for the selective adsorption of two competing cationic species at a highly charged planar interface. The cations differ in both their diameter (2 4.25 Å) valence (mono- divalent). Our show that general smaller or divalent cation is preferentially adsorbed electrode. In case when ion larger monovalent smaller, we find competitive situation: lower surface charges electrostatic advantage ions dominates, whereas...

Calcium-selective ion channels often contain a selectivity filter made of similar amino acids, rich in carboxlylates, although the ${\mathrm{Ca}}^{2+}$ affinities these range from micromolar to millimolar. To understand physical mechanism for this affinities, we use grand canonical Monte Carlo simulations study competition ${\mathrm{Na}}^{+}$ and reduced model Ca channel. We show that affinity is increased dramatically when both volume dielectric coefficient protein are reduced.

Our implicit-solvent model for the estimation of excess chemical potential (or, equivalently, activity coefficient) electrolytes is based on using a dielectric constant that depends thermodynamic state, namely, temperature and concentration electrolyte, ε(c, T). As consequence, split into two terms corresponding to ion-ion (II) ion-water (IW) interactions. The II term obtained from computer simulation Primitive Model electrolytes, while IW estimated Born treatment. In our previous work [J....

We propose a procedure to compute the steady-state transport of charged particles based on Nernst-Planck (NP) equation electrodiffusion. To close NP and establish relation between concentration electrochemical potential profiles, we introduce Local Equilibrium Monte Carlo (LEMC) method. In this method, Grand Canonical simulations are performed using specified for distinct volume elements. An iteration that self-consistently solves flux continuity equations with LEMC is shown converge...

Na channels that produce the action potentials of nerve and muscle include a selectivity filter formed by both positively negatively charged amino acid residues in molecular pore. Here we present Monte Carlo simulations equilibrium ion absorption such system. Ions are treated as hard spheres uniform dielectric. Tethered carboxylate groups known to line channel represented restricted region channel. Consistent with experiments, find (1) Ca2+ into exceeds Na+ only when concentration is some...

We apply a different version of the density functional theory, given by Pizio, Patrykiejew, and Sokolowski [J. Chem. Phys. 121, 11957 (2004)], for nonuniform restricted primitive model an electrolyte solution to evaluate temperature dependence capacitance electric double layer. show that this theory is capable reproducing computer simulation data at quantitative level. In particular, reversal low temperatures predicted. This phenomenon has been difficult predict from theory. Further, also...

Two iterative procedures have been proposed recently to calculate the chemical potentials corresponding prescribed concentrations from grand canonical Monte Carlo (GCMC) simulations. Both are based on repeated GCMC simulations with updated excess until desired established. In this paper, we propose combining our robust and fast converging iteration algorithm [Malasics, Gillespie, Boda, J. Chem. Phys. 128, 124102 (2008)] suggestion of Lamperski [Mol. Simul. 33, 1193 (2007)] average in...

We investigate the individual activity coefficients of pure 1:1 and 2:1 electrolytes using our theory that is based on competition ion–ion (II) ion–water (IW) interactions (Vincze et al. J. Chem. Phys. 2010, 133, 154507). The II term computed from grand canonical Monte Carlo simulations basis implicit solvent model hard sphere ions with Pauling radii. IW Born’s treatment solvation experimental hydration free energies. two terms are coupled through concentration-dependent dielectric constant...