Biological membranes their structure

R. Harrison and G. G. Lunt, Biological Membranes -Their Structure and Function , Blackie, London, 1976. 

Harrison, R., and Luni, G. G. (1980). Biological Membranes Their Structure and Function. Blackie, Glasgow. 

Surfactants have been used for over 1000 years in everyday applications, for example as emulsifiers in cleaning and in foods. They occur widely in nature, where as a bilayer they constitute a vital structural unit of biological membranes. Their functionality derives from the molecular structure, with a polar (hydrophilic) head-group, which conveys water-solubility, being attached to a non-polar (hydrophobic) tail, which drives the formation of self-assembled aggregates (micelles). Other chapters in this volume detail the wide variety of chemical structures that can form the polar groups (ionic, nonionic, zwitterionic, etc.) and tail structures. 

Just how fast can proteins move in a biological membrane Many membrane proteins can move laterally across a membrane at a rate of a few microns per minute. On the other hand, some integral membrane proteins are much more restricted in their lateral movement, with diffusion rates of about 10 nm/sec or even slower. These latter proteins are often found to be anchored to the cytoskeleton (Chapter 17), a complex latticelike structure that maintains the cell s shape and assists in the controlled movement of various substances through the ceil. 

Ion-selective bulk membranes are the electro-active component of ion-selective electrodes, which sense the activity of certain ions by developing an ion-selective potential difference according to the Nernst equation at their phase boundary with the solution to be measured. The main differences to biological membranes are their thickness and their symmetrical structure. Nevertheless they are used as models for biomembranes. 

The first two volumes in the series New Comprehensive Biochemistry appeared in 1981. Volume 1 dealt with membrane structure and Volume 2 with membrane transport. The editors of the last volume (the present editor being one of them) tried to provide an overview of the state of the art of the research in that field. Most of the chapters dealt with kinetic approaches aiming to understand the mechanism of the various types of transport of ions and metabolites across biological membranes. Although these methods have not lost their significance, the development of molecular biological techniques and their application in this field has given to the area of membrane transport such a new dimension that the appearance of a volume in the series New Comprehensive Biochemistry devoted to molecular aspects of membrane proteins is warranted. 

Fluorescence is also a powerful tool for investigating the structure and dynamics of matter or living systems at a molecular or supramolecular level. Polymers, solutions of surfactants, solid surfaces, biological membranes, proteins, nucleic acids and living cells are well-known examples of systems in which estimates of local parameters such as polarity, fluidity, order, molecular mobility and electrical potential is possible by means of fluorescent molecules playing the role of probes. The latter can be intrinsic or introduced on purpose. The high sensitivity of fluo-rimetric methods in conjunction with the specificity of the response of probes to their microenvironment contribute towards the success of this approach. Another factor is the ability of probes to provide information on dynamics of fast phenomena and/or the structural parameters of the system under study. 

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