Equations Of Membrane Biophysics

Equations of Membrane Biophysics provides an introduction to the relevant principles of thermodynamics, kinetics, electricity, surface chemistry, electrochemistry, and other mathematical theorems so that the quantitative aspects of membrane phenomena in model and biological systems could be described. The book begins by introducing several phenomena that arise across membranes, both artificial and biological, when different driving forces act across them. This is followed by separate chapters on thermodynamic principles related to properties of dilute aqueous electrolyte solutions along with a review of the principles of electrostatics, electrochemical principles, Fick's laws of diffusion, and the rate theory of diffusion; the quantitative aspects of the electrochemistry of solutions and membranes, and the quantitative relations between charges and electrostatic potentials related to surfaces and interfaces; and membrane theories pertaining to electrical potentials arising across a variety of membranes. Subsequent chapters deal with steady-state thermodynamic approaches to several transport phenomena in membranes; tissue impedance, cable theory, and Hodgkin-Huxley equations; and fluctuation analysis of the electrical properties of the membrane.

Physics, mathematics and chemistry all play a vital role in understanding the true nature and functioning of biological membranes, key elements of living processes. Besides simple spectroscopic observations and electrical measurements of membranes we address in this book the phenomena of coexistence and independent existence of different membrane components using various theoretical approaches. This treatment will be helpful for readers who want to understand biological processes by applying both simple observations and fundamental scientific analysis. It provides a deep understanding of the causes and effects of processes inside membranes, and will thus eventually open new doors for high-level pharmaceutical approaches towards fighting membrane- and cell-related diseases.

A basic tenet of present day biophysics is that flows in biological systems are causally related to forces. A large and growing fraction of membrane biophysics is devoted to an exploration of the quantitative relationship between forces and flows in order to understand both the nature of biological membranes and the processes that take place on and in these membranes. This is why the discussion of the nature of diffusion is so important in any formal development of membrane bio physics. This was equally true twenty years ago when tracers were just beginning to be used for the measurement of m.

This book summarizes the current status of research on bilayer lipid membranes (planar lipid bilayers and spherical liposomes). In addition to describing the properties of lipid bilayers and examining biomembrane phenomena, the book has two other objectives. The first is to present practical methods for the formation and study of lipid bilayers with either aqueous or metal-lipid bilayer interfaces. The second aim is to treat planar lipid bilayers as a new type of interfacial adsorption phenomena. The first nine chapters cover properties of biomembranes, basic principles of membrane biophysics, transport, electrochemistry, physiology, bioenergetics, and photobiology. Chapter 10 presents the following topics: lipid bilayers in medicine, supported lipid bilayers as sensors, a short discussion of liposomes, and solar energy transduction via semiconductor septum photovoltaic cells based on natural photosynthesis.

The present manual contains a collection of laboratory instructions used during an international training course on membrane biophysics which was held at Homburg in the fall of 1966. The selection of the topics dealt with in the various chapters depended on the scientific interest of the available teachers and on the availability of the necessary equipment in our laboratories. Thus, the material included in this volume does not add up to a systematic course in membrane biophysics. Instead it represents a more fortuitous collection of laboratory problems. In addition, some authors place more emphasis on teaching the more technical aspects of a method whereas others are primarily concerned with the demonstra tion of a significant biological phenomenon. Nevertheless, in spite of such differences of emphasis and a somewhat haphazard choice of a few methods and phenomena among many others of similar importance, it was felt that the publication of the material is desirable. Since no other laboratory manual exists so far, the present laboratory problems which were tested in actual practice may serve as a useful basis for the shaping of further training courses or for laboratory courses for graduate students in biophysics and physiology. Our thanks are due to the authors and the publisher who were patient and kind enough to cooperate with the editors during the long period between the end of the course and the appearance of the book.

The material of this volume was originally planned to be incorporated in the preceding monograph Mechanics and Energetics of Biological Transport. A separate and coherent treatment ofthe variety of bioelectrical phenomena was considered preferable, mainly for didactic reasons. Usually, the biologist has to gather the principles of bioelectricity he needs from different sources and on different levels. The present book intends to provide these principles in a more uniform context and in a form adjusted to the problems of a biol ogist, rather than of a physicist or electrical engineer. The main emphasis is put on the molecular aspect by relating the bioelectrical phenomena, such as the membrane diffusion potentials, pump potentials, or redox potentials, to the properties of the membrane concerned, and, as far as pOSSible, to specific steps of transport and metabolism of ions and nonelectrolytes. Little space is devoted to the familiar and widely used representation of bioelectrical phe nomena in terms of electrical networks, of equivalent circuits with batteries, resistances, capacities etc. In order to elucidate the basic principles, the formal treatment is kept as simple as pOSSible, using highly Simplified models, based on biological systems. The corresponding equations are derived in two ways: kinetically, i. e. in terms of the Law of Mass Action, as well as energetically, i. e. , in terms of Nonequilibrium Thermodynamics.