Showing papers by "Douglas B. Kell published in 1988"

Mechanisms for the interaction between nonstationary electric fields and biological systems II. Nonlinear dielectric theory and free-energy transduction

Abstract: A discussion of nonlinear dielectric phenomena and their relationship to freeenergy transduction in biological systems is given. It transpires that the conditions required for observing the nonlinear dielectric behavior of biological membranes can be expected under easily realizable circumstances, and may potentially form the basis for powerful techniques for studying membrane and other proteins in their native environment. We develop a nonlinear dielectric theory, which generalizes the dielectric permittivity to include real and imaginary parts of harmonics of the fundamental frequency. An analytical relationship is derived between these permittivities and the kinetic constants of a model protein. Of special relevance is the occurrence of higher harmonics in the dielectric displacement even when the exciting electric field consists of a single sinusoidal frequency. This is manifested by the analytical result that the corresponding higher order permittivities are in general not equal to zero, as ...

Mechanisms for the interaction between nonstationary electric fields and biological systems I. Linear dielectric theory and its limitations

Abstract: Our interest in the role of electric interactions in enzyme catalysis and biological free-energy transduction prompts us to examine to what extent dielectric phenomena, experiments, and theory may bear on these issues. In this paper we review linear dielectric theory and show that issues of interest for catalysis and free energy transduction lie outside the scope of linear dielectric theory (even in a somewhat extended form). This is due to the rather strict limitations imposed by the definition of linearity, which we discuss in detail. The review given here will provide a basis for the elaboration of nonlinear dielectric theory able to address the interaction between nonstationary electric fields and enzyme catalysis.

Growth energetics of Clostridium sporogenes NCIB 8053: modulation by CO2

Abstract: The effects of the partial pressure of carbon dioxide on the growth energetics of Clostridium sporogenes NCIB 8053 grown in chemostat culture were investigated in defined minimal media. Both the ‘maintenance’ requirements and the growth yield coefficients were dependent upon the partial pressure of carbon dioxide in otherwise glucose-limited cultures. Since growth yield coefficients decreased along with the apparent ‘maintenance’ requirements in essential amino acid/fatty acid medium when the partial pressure of carbon dioxide was increased above 0.5 atm, the occurrence of some type of metabolic uncoupling seemed likely. By contrast, when the organism was grown in amino acid complete medium both the maintenance requirements and the growth yield coefficients were increased when the partial pressure of carbon dioxide was raised above 0.5 atm partial pressure of carbon dioxide, suggesting an increased efficiency of growth. A futile cycle involving carbon dioxide is proposed as a factor contributing to the variable extent of free energy dissipation within this organism.