The fluid-mosaic model of membrane structure formulated by Singer and Nicolson in the early 1970s has proven to be a durable concept in terms of the principles governing the organization of the constituent lipids and proteins. During the past 30 or so years a great deal of information has accumulated on the composition of various cell membranes and how this is related to the dif ferent functions that membranes perform. Nevertheless, the task of explaining particular functions at the molecular level has been hampered by lack of struc tural detail at the atomic level. The reason for this is primarily the difficulty of crystallizing membrane proteins which require strategies that differ from those used to crystallize soluble proteins. The unique exception is bacteriorhodopsin of the purple membrane of Halobacterium halobium which is interpolated into a membrane that is neither fluid nor in a mosaic configuration. To date only 50 or so membrane proteins have been characterised to atomic resolution by diffraction methods, in contrast to the vast data accumulated on soluble proteins. Another factor that has been difficult to explain is the reason why the lipid compliment of membranes is often extremely complex. Many hundreds of different molecular species of lipid can be identified in some membranes. Remarkably, the particular composition of each membrane appears to be main tained within relatively narrow limits and its identity distinguished from other morphologically-distinct membranes.

This volume brings together information on membrane organization and dynamics from a variety of spectroscopic, microscopic and simulation approaches, spanning a broad range of time scales. The implication of such dynamic information on membrane function in health and disease is a topic of contemporary interest. The chapters cover various aspects of membrane lipid and protein dynamics, explored using a battery of experimental and theoretical approaches. The synthesis of information and knowledge gained by utilizing multiple approaches will provide the reader with a comprehensive understanding of the underlying membrane dynamics and function, which will help to develop robust dynamic models for the understanding of membrane function in healthy and diseased states. In the last few years, crystal structures of an impressive number of membrane proteins have been reported, thanks to tremendous advances in membrane protein crystallization techniques. Some of these recently solved structures belong to the G protein-coupled receptor (GPCR) family, which are particularly difficult to crystallize due to their intrinsic flexibility. Nonetheless, these static structures do not provide the necessary information to understand the function of membrane proteins in the complex membrane milieu. This volume will address the dynamic nature of membrane proteins within the membrane and will provide the reader with an up-to date overview of the theory and practical approaches that can be used. This volume will be invaluable to researchers working in a wide range of scientific areas, from biochemistry and molecular biology to biophysics and protein science. Students of these fields will also find this volume very useful. This book will also be of great use to those who are interested in the dynamic nature of biological processes.

The first volume of the Handbook deals with the amazing world of biomembranes and lipid bilayers. Part A describes all aspects related to the morphology of these membranes, beginning with the complex architecture of biomembranes, continues with a description of the bizarre morphology of lipid bilayers and concludes with technological applications of these membranes. The first two chapters deal with biomembranes, providing an introduction to the membranes of eucaryotes and a description of the evolution of membranes. The following chapters are concerned with different aspects of lipids including the physical properties of model membranes composed of lipid-protein mixtures, lateralphase separation of lipids and proteins and measurement of lipid-protein bilayer diffusion. Other chapters deal with the flexibility of fluid bilayers, the closure of bilayers into vesicles which attain a large variety of different shapes, and applications of lipid vesicles and liposomes. Part B covers membrane adhesion, membrane fusion and the interaction of biomembranes withpolymer networks such as the cytoskeleton. The first two chapters of this part discuss the generic interactions of membranes from the conceptual point of view. The following two chapters summarize the experimental work on two different bilayer systems. The next chapter deals with the process ofcontact formation, focal bounding and macroscopic contacts between cells. The cytoskeleton within eucaryotic cells consists of a network of relatively stiff filaments of which three different types of filaments have been identified. As explained in the next chapter much has been recently learned aboutthe interaction of these filaments with the cell membrane. The final two chapters deal with membrane fusion.

Biological membranes protect cells and organelles from the surrounding environment, but serve also as organising platforms for physiological processes such as cell signalling. The hydrophobic core of membranes is composed of lipids and proteins influencing each other. Local membrane composition and properties define its molecular organisation and, in this way, regulate the function of all associated molecules. Therefore, studying interactions of components, biophysical properties and overall membrane dynamics provides essential information on its function in the context of cell activities. Such knowledge can contribute to biomedical fields such as pharmacology, immunology, neurobiology and many others. The goal of the Research Topic entitled ‘Molecular organisation of membranes: where biology meets biophysics’ was to provide a comprehensive platform for publishing articles, reviews and opinions focused on membrane organisation and the forces behind its heterogeneous and dynamic structure. We collected 11 works which cover topics as diverse as general membrane organisation models, membrane trafficking and signalling regulation, biogenesis of caveolae, protein-lipid interactions and the importance of membrane-associated tetraspanins networks. The prevalent theme was the existence of membrane nanodomains. To this point, new emerging technologies are presented which own the power to bring a novel insight on how membrane nanodomains are formed and maintained and what is their function. We believe that the collection of works in this Research Topic brings forward some important questions which will stimulate further research in this difficult but exciting field.

Current Topics in Membranes is targeted toward scientists and researchers in biochemistry and molecular and cellular biology, providing the necessary membrane research to assist them in discovering the current state of a particular field and in learning where that field is heading. This volume offers an up to date presentation of current knowledge in the field of Lipid Domains. Written by leading experts Contains original material, both textual and illustrative, that should become a very relevant reference material The material is presented in a very comprehensive manner Both researchers in the field and general readers should find relevant and up-to-date information

The study of membranes has become of high importance in the fields of biology, pharmaceutical chemistry and medicine, since much of what happens in a cell or in a virus involves biological membranes. The current book is an excellent introduction to the area, which explains how modern analytical methods can be applied to study biological membranes and membrane proteins and the bioprocesses they are involved to.

Abstract: The plasma membrane of mammalian cells is depicted as a two-dimensional hybrid material which is compartmentalized into submicron-sized domains. These membrane domains play a pivotal role in cellular signaling processes due to selective recruitment of specific cell surface receptors. The structural dynamics of the membrane domains and their exact biological functions are, however, still unclear, partially due to the wave nature of light, which limits the optical resolution in the visible light to approximately 400 nm in conventional optical microscopy. Here, we provide a non-fluorescence based approach for monitoring distance changes on subdiffraction limit length scales in a conventional far-field optical microscope. This approach, which is referred to as plasmon coupling microscopy (PCM), utilizes the distance dependent near-field coupling between noble metal nanoparticle (NP) labels to resolve close contacts on the length scale of approximately one NP diameter. We firstly utilize this PCM strategy to resolve interparticle separations during individual encounters of gold NP labeled fibronectin-integrin complexes in living HeLa cells. We then further refine this ratiometric detection methodology by augmenting it with a polarization-sensitive detection, which enables simultaneous monitoring of the distance and conformation changes in NP dimers and clusters. We apply this polarization resolved PCM approach to characterize the structural lateral heterogeneity of cell membranes on sub-micron length scales. Finally, we demonstrate that PCM can provide quantitative information about the structural dynamics of individual epidermal growth factor receptor (ErbB1)-enriched membrane domains in living cells.