Biomedical subjects

HK Tsao

Publications and source records attributed to HK Tsao.

5 recordsLinked to original sources

PubMed2001

The Electrostatic Interaction of a Charged Particle with a Surface: The Effect of Surface Charge Rearrangement.

In this paper we investigate the electric interaction between a charged particle and a surface in which the charged ions are capable of moving in response to the electric potential disturbance caused by the approach of the charged particle. Such surfaces include ionic surfactants distributed in air-water interface and charged lipids in bilayer membranes. On the basis of the mean field theory, the free energy of the system, which includes the electrostatic internal energy and the entropy of the mobile ions and surface ions, can be written down. The surface charge-potential relation is then derived by the calculus of variation. When the potential disturbance is small enough, a linear charge regulation model is obtained. The interaction energy associated with a long rod parallel to the interface is studied and an analytical expression is obtained. When a rod approaches an oppositely charged surface, the interaction can change from attraction to repulsion, depending on the ratio of the characteristic regulation length to the Debye length. At low surface charge density, the surface behaves as under the condition of constant charge density and acts as that of constant potential for high enough charge density. Copyright 2001 Academic Press.

Journal Article↗

PubMed2000

Electroosmotic Flow through an Annulus.

The electro-osmosis through an annulus is investigated. The electric potential and flow velocity profile are obtained by solving the linearized Poisson-Boltzmann equation and the Stokes equation. Both the thin and thick double layer limits are analyzed. Under the condition of thin double layer, the electro-osmotic mobility can be described by the Helmholtz-Smoluchowski equation with a geometry-dependent correction factor. There exist net flows even for zero area-averaged surface charge density due to the curvature differences between the inner and outer walls. The flow direction is determined by the sign of the charge on the inner cylinder. We also found that under certain circumstances the flow direction in an annulus is opposite to that in a capillary with the same sign of the net charge. Copyright 2000 Academic Press.

Journal Article↗

PubMed1999

The Electrostatic Interactions between Two Corrugated Charged Planes.

The surfaces of association colloids often undergo undulating motion due to thermal fluctuations. The electrostatic interactions between two charged planes of arbitrary corrugation are investigated on the basis of the Poisson-Boltzmann equation under the Debye-Hückle approximation. The surfaces are parallel and subject to the spatial periodicity of the amplitude A and wavelength q(-1). When the amplitude is small compared to the wavelength, i.e., (qA)(2) << 1, the electric field can be calculated by using the perturbation method. The interaction free energy is then obtained for surfaces associated with the condition of either constant surface potential or constant surface charge density during interactions. The effects of the amplitude and phase angle on the interaction energy are discussed and asymptotic expressions are obtained when the mean separation is large compared to the amplitude. At the same mean separation, the interaction energy for the corrugated surfaces is always higher than that for the planar surfaces. In other words, undulation enhances the electrostatic repulsion. The repulsive energy is minimum when the two surfaces are in-phase and maximum for the out-of-phase mode. Copyright 1999 Academic Press.

Journal Article↗

PubMed1998

Electrostatic Interactions between Two Plates Covered with Charge-Regulation Layers.

The interaction energy between two plates covered with charge-regulation layers is calculated based on a linearized Poisson-Boltzmann equation. By a comparison with the exact solution, the accuracy of the approximate solutions obtained by linear superposition approximation and the regular perturbation method can be examined. The range of the validity for both approximations is therefore determined. These results may shed some light on the interaction between two spheres, which is complicated and often investigated by the approximate approaches. Copyright 1998 Academic Press.

Journal Article↗

PubMed1997

Microcalorimetric Studies of the Interactions of Lysozyme with Immobilized Cu(II): Effects of pH Value and Salt Concentration

In this investigation, employing a highly sensitive microcalorimeter, we measure the influence of pH value and salt concentration on the heat of interaction between lysozyme and CS-IDA-Cu(II) gel. The direct enthalpy measurement of the interaction provides thermodynamic information regarding the binding behavior of lysozyme toward the immobilized metal ion. The binding enthalpy altered by adsorbed lysozyme at various pH values and salt concentrations are measured. The findings, along with the reported binding isotherm, are discussed herein.

Journal Article↗