Biologies electrical properties

Membranes (Biology)—Electric properties—Congresses. 2. Electrophysiology—Congresses. 

Today, electrochemistry is a rigorous science concerned with the quantitative relations among the chemical, surface, and electrical properties of systems. Electrochemistry has strong finks to many other fields of science. Electrochemical concepts proved particularly fruitful for studying and interpreting a number of very important biological processes. 

An analytical technique that exploits magnetic fields to analyze molecules on the basis of their mass and electrical properties to determine (a) qualitative separation of mixtures of inorganic and organic species, (b) quantitative determination of the amount of substance, (c) isotopic abundance of atoms in simple and complex molecules, and (d) structures of biological and other organic molecules by use of special fragmentation methods. 

Throughout the text we will relate polymer structure to the properties of the polymer. Polymer properties are related not only to the chemical nature of the polymer, but also to such factors as extent and distribution of crystallinity, distribution of polymer chain lengths, and nature and amount of additives, such as fillers, reinforcing agents, and plasticizers, to mention a few. These factors influence essentially all the polymeric properties to some extent including hardness, flammability, weatherability, chemical stability, biological response, comfort, flex life, moisture retention, appearance, dyeability, softening point, and electrical properties. 

BIOELECTROCHEMISTRY. Application of the principles and techniques of electrochemistry to biological and medical problems. It includes such surface and interfacial phenomena as the electrical properties of membrane systems and processes, ion adsorption, enzymatic clotting, transmembrane pH and electrical gradients, protein phosphorylation, cells, and tissues. 

Biological Implications of Structural and Electrical Properties of Lipids. It is rather obvious that the structure of lipids is very important in connection with the function of living cells since most physiological processes occur in lipid environment. There is, for example, evidence that lipid-protein complexes are necessary for the proper functioning of mitochondria (56). Although lipids are most important in providing a suitable material for functional complexes (ionic channels, electron transport systems, receptor units, etc.), their own physical properties are certainly... 

Ion-selective field-effect transistors (ISFETs) are ion sensors that combine the electric properties of gate-insulator field-effect transistors and the electrochemical properties of ion-selective electrodes (ISEs). ISFETs have attracted much attention for clinical and biomedical fields because they could contain miniaturized multiple sensors and could be routinely used for continuous in vivo monitoring of biological fluid electrolytes (e.g., Na+, K+, Ca +, Cl", etc.) during surgical procedures or at the bedside of the patients in clinical cate unit (2). 

Field forces due to the induced dipole moment of the field have been listed as evidence of nonthermal action of electric fields on biologic systems. However, the effects require fairly large field strengths, frequently above those that give rise to heating or stimulation of excitable tissues. The field forces also depend on the electric properties of the particle considered and its environment. 

In understanding the electrical characteristics of biological materials such as tissue which is a complex, inhomogeneous, anisotropic, and nonlinear material, we feel it is necessary to first understand the electrical properties of the simpler biological fluids. Additionally since the fields in the vicinity of membranes may be quite large ( xlO 4 volts/cm) it is important to understand the high field behavior as well as the more commonly measured small signal characteristics. 

The electrical properties of polyelectrolyte complexes are more closely related to those of biologically produced solids. The extremely high relative dielectric constants at low frequencies and the dispersion properties of salt-containing polyelectrolyte complexes have not been reported for other synthetic polymers. Neutral polyelectrolyte complexes immersed in dilute salt solution undergo marked changes in alternating current capacitance and resistance upon small variations in the electrolyte concentration. In addition, their frequency-dependence is governed by the nature of the microions. As shown in... 

Surface Charge of Liposomes The electrical properties of liposomal surfaces can influence the physical stability of liposomal dispersions during storage as well as the behavior of liposomes in the biological milieu and their interaction with cells [47,81],... 

The electric properties of biological membranes and proteins depend on the potential distribution and the electrostatic interaction energy of their charges (see e.g.. Refs [1 ]). The potential distribution J/(r) at position r around fixed point charges with a distribution p(r) in a uniform medium of relative permittivity is described by the Poisson equation,... 

Pure lipid membranes are electrical insulators with a specific capacitance of 1 tiF/cm, which separate two electrolytic compartments. The conductance of biological membranes is maiifly determined by highly specialized proteins that act as ion chaimels. For supported membranes to mimic the electrical properties of a biological membrane, it is necessary to measure its electrical characteristics. Even very small defects that are not... 

Conjugated macrocyclic compounds play important roles in a number of important biological reactions and there has been a resurgence of interest in the electrical properties of such compounds. Although in both biochemical and semisuperconducting applications, side chains fulfill an important mechanistic role," the central conjugated ring is clearly essential. The compound 5,14-dihydrodibenzo[6,i] [1,4,8,11] tetraazacyclotetradecine (TADA-H2) is a suitable parent system for biochemical and electrical studies. There are problems with some published syntheses and physical properties. ... 

Electrical properties of membranes. Biological membranes serve as barriers to the passage of ions and polar molecules, a fact that is reflected in their high electrical resistance and capacitance. The electrical resistance is usually 10 ohms cm, while the capacitance is 0.5-1.5 microfarad (pF) cm . The corresponding values for artificial membranes are 10 ohms cm and 0.6 - 0.9 pF cm . The lower resistance of biological membranes must result from the presence of proteins and other ion-carrying substances or of pores in the membranes. The capacitance values for the two types of membrane are very close to those expected for a bilayer with a thickness of 2.5 nm and a dielectric constant of 2. 4 The electrical potential gradient is steep. 

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