Herwig J. Hilderson – författare

Corpora non agunt nisi fixata. This old saying of Ehrlich's describing the physi- ological role of receptors and their ligands might be paraphrased into Corpora non ambulant nisi fixata when considering lipid transport between and within cells. Volume 16 of Subcellular Biochemistry is intended to bring the reader up to date with this young field. Indeed, lipid transfer proteins have only recently become the subject of a more systematic study. In this book the current status and the emerging trends are discussed. Chapters cover protein-mediated transfer of fatty acids, phospholipids, phosphatidylinositol, glycolipids, dolichol, retinoids, and cholesterol in animal, plant, yeast, and other eukaryotic cells. Details are included of the study of lipid transport proteins by means of fluorescent phos- pholipid analogues and of the lipid transfer proteins as probes of membrane structure and function, as well as spontaneous lipid transfer as it occurs between biological membranes. Some of the chapters should be read in conjunction with Volume 13 of this series, devoted to fluorescence studies on biological mem- branes, in particular Chapter 2 (Somerharju et al.) concentrating on studies in which fluorescent phospholipid analogues have been used. Chapter 10 (Bill- heimer and Reinhart), dealing with cholesterol trafficking, should be compared with Chapter 12 of Volume 13 (Van Blitterswijk), pointing to the existence of a preferential association of cholesterol with sphingomyelin, which drags choles- terol to the plasma membrane. In one chapter (Chapter 8: Van Dessel et al.

Membrane fusion and targeting processes are tightly regulated and coordinated. Dozens of proteins, originating from both the cytoplasm and membranes are involved. The discovery of homologous proteins from yeast to neurons validates a unified view. Although much is known about the interfering proteins, the events occurring when two lipid bilayers actually fuse are less clear. It should be remembered that lipid bilayers behave like soap-bubbles fusing when meeting each other. In this respect interfering proteins should be considered as preventing undesirable and unnecessary fusion and eventually directing the biological membrane fusion process (when, where, how, and overcoming the activation energy). In this latest volume in the renowned Subcellular Biochemistry series, some aspects of fusion of biological membranes as well as related problems are presented. Although not complete, there is a lot of recent information including on virus-induced membrane fusion. The contributors of the chapters are all among the researchers who performed many of the pioneering studies in the field.

Membrane fusion and targeting processes are tightly regulated and coordinated. Dozens of proteins, originating from both the cytoplasm and membranes are involved. The discovery of homologous proteins from yeast to neurons validates a unified view. Although much is known about the interfering proteins, the events occurring when two lipid bilayers actually fuse are less clear. It should be remembered that lipid bilayers behave like soap-bubbles fusing when meeting each other. In this respect interfering proteins should be considered as preventing undesirable and unnecessary fusion and eventually directing the biological membrane fusion process (when, where, how, and overcoming the activation energy). In this latest volume in the renowned Subcellular Biochemistry series, some aspects of fusion of biological membranes as well as related problems are presented. Although not complete, there is a lot of recent information including on virus-induced membrane fusion. The contributors of the chapters are all among the researchers who performed many of the pioneering studies in the field.

In mammalian cells many physiological processes rely on the dynamics of the organization of lipids and proteins in biological membranes. The topics in this volume deal with physicochemical methods in the study of biomembranes. Some of them have a long and respectable history in the study of soluble proteins and have only recently been applied to the study of membranes. Some have tradi­ tionally been applied to studies of model systems of lipids of well-defined com­ position, as well as to intact membranes. Other methods, by their very nature, apply to organized bilayers comprised of both protein and lipid. Van Meer and van Genderen provide us with an introduction to the field (Chapter I). From their personal perspective regarding the distribution, trans­ port, and sorting of membrane lipids, they formulate a number of biologically relevant questions and show that the physicochemical methods described in this book may contribute in great measure to solving these issues. The methods of analytical ultracentrifugation have served faithfully for 60 years in the study of water-soluble proteins. The use of detergent extraction of membrane proteins, and the manipulation of density with H20/D20 mixtures, has extended this technique to the study of proteins, and in particular their interactions, from biological membranes. As described by Morris and Ralston in Chapter 2, this technique can be used to determine a number of important properties of proteins.

As stated by its first editor, Dr. D. B. Roodyn, the primary goal of the series Subcellular Biochemistry is to achieve an integrated view of the cell by bringing together results from a wide range of different techniques and disciplines. This volume deals with the applications of fluorescence spectroscopy to membrane research. It seeks to present complementary biochemical and bio­ physical data on both the structure and the dynamics of biological membranes. Biophysics and biochemistry are improving more and more in their ability to study biomembranes, overlapping somewhat in this area and explaining the functioning of the whole cell in terms of the properties of its individual com­ ponents. Therefore, we have brought together an international group of experts in order to report on and review advances in fluorescence studies on biological membranes, thereby highlighting subcellular aspects. The first chapters present a critical evaluation of the current applications of dynamic and steady-state fluorescence techniques. Subsequent chapters dis­ cuss more specific applications in cells, biological membranes, and their con­ stituents (lipids, proteins).