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M Hernández-Contreras

Publications and source records attributed to M Hernández-Contreras.

8 recordsLinked to original sources
PubMed2005

Structural thermodynamics of lamellar cationic lipid-DNA complex: DNA compressibility modulus.

We have studied theoretically the compressibility modulus B of DNA and complexation adsorption isotherms of DNA and lipids, as a function of DNA spacing d(DNA) and NaCl electrolyte concentration, respectively, in isoelectric states of lamellar DNA/cationic lipid (CL) self-assemblies. The electrostatic free energy derived from the Poisson-Boltzmann theory predicts partial agreement with measured B values for interhelical separations d(DNA)>33 A when use is made of a fit of hydration repulsion from bulk DNA hexagonal phases in solution. For lower interchain separations the prediction worsens due to the hydration interaction that overcomes the electrostatic contribution. An exact match of the system's counterion electrochemical potentials and the coions of salt in aqueous phase leads to the electrostatic part of the free energy that renders isotherms of d(DNA) versus ionic strength in qualitative consistency with general trends of available experimental data of CL-DNA complexes.

Adsorption↗
PubMed2004

Phase evolution of lamellar cationic lipid-DNA complex: steric effect of an electrolyte.

The complexation isotherms of DNA plus lipids of a symmetric lamellar cationic lipid-DNA system were determined within a mean field free energy. The free energy incorporates the ion's finite size of NaCl simple electrolyte in solution and makes use of known structure data on this complex. The results for the predicted isotherms are in qualitative agreement with the trends of the experimental data for this property.

Cations↗
PubMed2003

Transport properties of ferrofluids.

Long-time self-diffusion coefficients of ferrofluid suspensions are derived from an effective Langevin equation approach. The dependences of these transport properties on the volume fraction of particles and the strength of interparticle interaction are investigated. Strong reduction of the rotational and the translational Brownian motion of the particles is manifested upon increase of particle-particle interaction or ferrofluid concentration.

Journal Article↗
PubMed2001

Electrostatic correlation force of discretely charged membranes.

The total force between two like charged surfaces is investigated as a function of counterion concentration in aqueous solution and surfaces distance of separation. A smooth and a discrete density of surface charge sigma(s) lead to differences in the force distance curve at high sigma(s), which are negligible for low surface charge. The total force per unit area with divalent counterions is an oscillating function of sigma(s). At fixed surfaces separation and region of attraction (increasing sigma(s)), there is a variation in its strength that results from a competition between the ideal kinetic and ion-ion correlation force components as predicted from the anisotropic hypernetted chain approximation.

Biophysical Phenomena↗
PubMed1999

Surface hydrodynamics on a freely standing layer of a polymer solution.

The dispersion relation and the power spectrum of the surface modes on a surface-active, freely standing film of a concentrated polymer solution are studied with a two-component fluid model of a viscoelastic material. The diagram of bending modes is obtained from an asymptotic analysis of the dispersion equation when the bending rigidity modulus is the main elastic effect on the layer interface. The resulting dynamical structure factor provides the characteristic squeezing and undulation surface modes of the interfaces driven by thermal fluctuations or by a weak external perturbation. The effect of interfacial and bulk elastic properties on the power spectrum of the scattered light is studied. In the regime of an elastic solution, finite-thickness effects and bulk elastic properties of the layer sustain a train of elastic peaks when the wavelength of thermal fluctuations is comparable to the thickness of the layer. Interfacial elasticity properties increase the strength and shift all resonance frequency peaks producing a less intense quasielastic spectrum around zero frequency.

Journal Article↗