Il capitano generale lagrimo per allegrezza e nomino quel capo: Deseado, perehe l'avevamo gia gran tempo desiderato. Antonio Pigafetta Il Primo Viaggo in torno al Mondo I would like to take some poetic license in introducing this volume in a way that seems appropriate for a country, like Chile, that Iooks to the ocean. I believe it was Heisenberg who compared different times in physics with sailing a ship. He said that most of the time we keep our ships in port, or in the protection of a bay. But on a few occasions we go into the open sea, and those occasions are really the great times in theoretical physics, when everything can change. It does not seem totally unwarranted to hope that we are now entering one of those times. In that spirit, I would like to mention a wonderful book, which in English would be called something like Chile, Or a Crazy Geography.

Ion channels allow us to see nature in all its magnificence, to hear a Bach suite, to smell the aroma of grandmother's cooking, and, in this regard, they put us in contact with the external world. These ion channels are protein molecules located in the cell membrane. In complex organisms, cells need to communicate in order to know about their metabolic status and to act in a coordinate manner. The latter is also accomplished by a class of ion channels able to pierce the lipid bilayer membranes of two adjacent cells. These intercellular channels are the functional subunits of gap junctions. Accordingly, the book is divided in two parts: the first part is dedicated to ion channels that look to the external world, and the second part is dedicated to gap junctions found at cell interfaces. This book is based on a series of symposia for a meeting on ion channels and gap junctions held in Santiago, Chile, on November 28-30, 1995. The book should be useful to graduate students taking the first steps in this field as well as a reference for the aficionado. The aim of the meeting was mainly to show the impact of various modern techniques, including cell biology, molecular biology, biophysics, and molecular­ genetics techniques in the study of these ubiquitous intrinsic membrane proteins. Molecular-genetics techniques paved the road to the manipulation of the channel­ forming molecules.

This book is a compilation of articles based on some of the talks given at the Centro de Estudios Cientificos (CECS) in Valdivia during the course of a celebration to th mark the 60 birthdays of Ramon Latorre and Enrico Stefani. Ramon Latorre is one of the most outstanding figures in channel Biophysics today. The first surprise is that he trained as a Biochemist! He soon, however, became a biophysicist through his work with Guayo (Eduardo) Rojas who guided him during his Ph. D thesis in the Laboratorio de Fisiologia Celular in Montemar. His work at N. I. H with Gerald Eherenstein and Harold Lecar constitutes one of the milestones of single ion channel Biophysics. This classical work, done in planar bilayers, set the basis for understanding voltage-dependent conductances with single channel studies and predates, by many years, later studies using patch clamping techniques. Ramon was one of the firsts to find and recognize the importance of calci- activated potassium channels and to begin a detailed study of channel properties. He pioneered the ideas of voltage and calcium modulation of the open probability and he added detailed studies of gating and its modulation by other ions.Ramon is also interested in permeation and selectivity and he produced classical studies on the number of water molecules in the channel and sites occupied by barium. Results and concepts that have recently taken front page as the structure of KcSa has been described.

The 2002 Pan-American Advanced Studies Institute School on Quantum Gravity was held at the Centro de Estudios Cientificos (CECS),Valdivia, Chile, January 4-14, 2002. The school featured lectures by ten speakers, and was attended by nearly 70 students from over 14 countries. A primary goal was to foster interaction and communication between participants from different cultures, both in the layman’s sense of the term and in terms of approaches to quantum gravity. We hope that the links formed by students and the school will persist throughout their professional lives, continuing to promote interaction and the essential exchange of ideas that drives research forward.This volume contains improved and updated versions of the lectures given at the School. It has been prepared both as a reminder for the participants, and so that these pedagogical introductions can be made available to others who were unable to attend. We expect them to serve students of all ages well.

This book is a compilation of articles based on some of the talks given at the Centro de Estudios Cientificos (CECS) in Valdivia during the course of a celebration to th mark the 60 birthdays of Ramon Latorre and Enrico Stefani. Ramon Latorre is one of the most outstanding figures in channel Biophysics today. The first surprise is that he trained as a Biochemist! He soon, however, became a biophysicist through his work with Guayo (Eduardo) Rojas who guided him during his Ph. D thesis in the Laboratorio de Fisiologia Celular in Montemar. His work at N. I. H with Gerald Eherenstein and Harold Lecar constitutes one of the milestones of single ion channel Biophysics. This classical work, done in planar bilayers, set the basis for understanding voltage-dependent conductances with single channel studies and predates, by many years, later studies using patch clamping techniques. Ramon was one of the firsts to find and recognize the importance of calci- activated potassium channels and to begin a detailed study of channel properties. He pioneered the ideas of voltage and calcium modulation of the open probability and he added detailed studies of gating and its modulation by other ions.Ramon is also interested in permeation and selectivity and he produced classical studies on the number of water molecules in the channel and sites occupied by barium. Results and concepts that have recently taken front page as the structure of KcSa has been described.

The 2002 Pan-American Advanced Studies Institute School on Quantum Gravity was held at the Centro de Estudios Cientificos (CECS),Valdivia, Chile, January 4-14, 2002. The school featured lectures by ten speakers, and was attended by nearly 70 students from over 14 countries. A primary goal was to foster interaction and communication between participants from different cultures, both in the layman’s sense of the term and in terms of approaches to quantum gravity. We hope that the links formed by students and the school will persist throughout their professional lives, continuing to promote interaction and the essential exchange of ideas that drives research forward.This volume contains improved and updated versions of the lectures given at the School. It has been prepared both as a reminder for the participants, and so that these pedagogical introductions can be made available to others who were unable to attend. We expect them to serve students of all ages well.

This volume is based on a meeting on Quantum Mechanics of Fundamental Systems, held December 17-20 of 1987, at the Centro de Estudios Cientificos de Santiago (CECS). The meeting was intended to review new developments in the field defined by its purposely vague title. We were especially interested in communicating important advances in a broad perspective and in a self-contained manner to a wide colleague- ship, and in particular to Latin American physicists. Whatever success we may have achieved in that direction would cer- tainly not have been possible without the help and generosity of many people. For their kind support we thank the Tinker Foundation, the Inter- national Centre for Theoretical Physics, the Ministere des Affaires Etrangeres et Service Culturel et de Cooperation Scientifique et Technique de France and the Centro Latinoamericano de Fisica. We are especially grateful to the Santiago College and to its principal, Rebeca Donoso, for allowing us to hold the meeting at that school when, at the last moment, we were deprived of the previously arranged meeting site.Last but not least we thank the participants for an extraordinary week and the CECS staff for performing, as usual, beyond any reasonable expectation.

The almost irresistible beauty of string theory has seduced many theoretical physicists in recent years. Even hardened men have been swept away by what they can already see and by the promise of even more. It would appear fair to say that it is not yet clear what form the theory will finally take and in what precise way it will relate to the physical world. However, it would seem equally fair to state that, most likely, strings are here to stay and will playa profound and central role in our conception of the universe. There is therefore a pressing need to provide both practicing physicists and advanced students with ways to master quickly, but soundly, the basic principles of the theory. The present volume is a step in that direction. It contains a lucid presentation of the basic principles of string theory in forms which may survive future developments. The book is an outgrowth of lectures given by Lars Brink and Marc Henneaux at the Centro de Estudios Cientificos de Santiago. The lectures covered in a self-contained manner different but complementary aspects of the foundations of string theory.

This book was originated from a series of lectures given in a course on the physical properties of biological membranes and their functional implica­ tions. The course was intended to allow students to get acquainted with the physical techniques used to study biological membranes. The experience was valuable and we feel that a detailed description of the procedures used and of various examples of the results obtained allowed many students to become familiar with a theme that is not often part of regular courses on membrane physiology or biophysics. This book is designed as a tutorial guide for graduate students interested in understanding how physical methods can be utilized to study the proper­ ties of biological membranes. It includes first a detailed description of applications of physical techniques-such as X-ray fiber diffraction methods (Chapter 1), 2H and 13C NMR spectroscopy (Chapter 2), and calorimetry (Chapter 3)-in the study of the properties of lipid model membranes. A description of how to measure molecular mobility in membranes (Chapter 4) follows, and the book concludes with three chapters in which biological membranes are the subject of study. Chapter 5 deals with the acetylcholine receptor and its membrane environment; Chapter 6 discusses how fluorescence techniques can be applied in the study of the calcium ATPase of sarcoplasmic reticulum; and Chapter 7 explains how protein­ lipid interactions modulate the function of the sodium and proton pumps.

The majesty of the icefields is beyond description. He who has been fortunate to be there once, remains bound forever. To a theoretical physicist working on black holes the icefields produce a familiar vertigo, the instinctive certainty of being confronted with something so simple and beautifully extreme that it must be of importance. The meeting whose proceedings are contained in this volume was conducted onboard of a vessel that went to the icefields, and the participants could literally set foot on them. It was expected that, for those who had not been there before, this would constitute a ritual of initiation. And so it did. For this reason we like to refer to the meeting as an expedition because, although it did not have the hardship, it had the spirit. After this foundational expedition there have been two others, this time both with spirit and hardship, one from Chile and one from Argentina. At the moment of this writing, a fourth, full-fledged airborne expedition to the icefields is about to depart from Valdivia. Many of the people of many nations who were on board of the Aquiles will take part in it. We look forward to its results, and to an ongoing exciting scientific adventure. Claudio Teitelboim Director, Centro de Estudios Cientfficos Valdivia, September 2001 v ACKNOWLEDGMENTS This volume is the result of the effort and generosity of many people and institutions.

From January 8-13,1990, distinguished physicists from many nations came to Chile to share with each other and with Latin American students exciting recent developments. The occasion was the third of a series of meetings on Quantum Mechanics of Fundamental Systems which are held every two years at the Centro de Estudios Cientificos de Santiago. This volume grew out from that gathering. The meeting was possible thanks to the generous support of the Tinker Foundation, the John D. and Catherine T. MacArthur Foundation, the International Centre for Theoretical Physics, the Ministere des AfIaires Etrangeres et Service Culturel et de Cooperation Scientifique et Technique de France, the Third World Academy of Sciences, and FONDECYT-Chile. The happy winds blowing over Chile at the time enhanced the joy provided by the beauty of the physics discussed. Claudio Teitelboim Jorge Zanelli Santiago, Chile vii Contents Chapter 1 Fractional Statistics in Quantum Mechanics Daniel P. Arovas 1. Introduction...1 2. Charge-Flux Composites...4 3. Dilute Anyon Gases ...6 4. Fractional Statistics in the Quantized Hall Effect ...8 5. Many-Body Theory of the Anyon Gas...16 6.Chern-Simons Field Theory and Fractional Statistics ...20 Appendix: Many Anyons in a Magnetic Field...23 . .

This book is based on a series of lectures for a course on ionic channels held in Santiago, Chile, on November 17-20, 1984. It is intended as a tutorial guide on the properties, function, modulation, and reconstitution of ionic channels, and it should be accessible to graduate students taking their first steps in this field. In the presentation there has been a deliberate emphasis on the spe­ cific methodologies used toward the understanding of the workings and function of channels. Thus, in the first section, we learn to "read" single­ channel records: how to interpret them in the theoretical frame of kinetic models, which information can be extracted from gating currents in re­ lation to the closing and opening processes, and how ion transport through an open channel can be explained in terms of fluctuating energy barriers. The importance of assessing unequivocally the origin and purity of mem­ brane preparations and the use of membrane vesicles and optical tech­ niques in the stUGY of ionic channels are also discussed in this section. The patch-clamp technique has made it possible to study ion channels in a variety of different cells and tissues not amenable to more conven­ tional electrophysiological methods. The second section, therefore, deals with the use of this technique in the characterization of ionic channels in different types of cells, ranging from plant protoplasts to photoreceptors.

The present volume originated from the workshop "Transduction in Biological Sys­ tems," held at the Marine Biological Station of the Universidad de Valparaiso, Mon­ temar, Chile, May 23-30, 1988, and contains contributions from most of the partici­ pants in the workshop. The title of both the workshop and the book reflects accurately the central theme discussed during several days of intense debate and profound intellectual exchange in the peaceful environment offered by the central coast of Chile. It was apparent that the workshop was a great success-a sentiment expressed by many seasoned attendees, some of whom dared opinions as strong as "It was the best ever." There is no single reason to explain why this workshop was so successful. Certainly instrumental was the incredible effort displayed by the Chilean Organizing Committee in selecting adequate facilities and in organizing social events that supplemented the scien­ tific sessions and provided an authentic fraternal environment for the participants. Equally important were the foreign participants, who enthusiastically gave of their time to take part in the event, and the students, who came from Chile as well as from several other Latin American countries, and who applied the necessary pressure in their repeated demands for scientific clarity, accuracy, and sincerity.

Ion channels allow us to see nature in all its magnificence, to hear a Bach suite, to smell the aroma of grandmother's cooking, and, in this regard, they put us in contact with the external world. These ion channels are protein molecules located in the cell membrane. In complex organisms, cells need to communicate in order to know about their metabolic status and to act in a coordinate manner. The latter is also accomplished by a class of ion channels able to pierce the lipid bilayer membranes of two adjacent cells. These intercellular channels are the functional subunits of gap junctions. Accordingly, the book is divided in two parts: the first part is dedicated to ion channels that look to the external world, and the second part is dedicated to gap junctions found at cell interfaces. This book is based on a series of symposia for a meeting on ion channels and gap junctions held in Santiago, Chile, on November 28-30, 1995. The book should be useful to graduate students taking the first steps in this field as well as a reference for the aficionado. The aim of the meeting was mainly to show the impact of various modern techniques, including cell biology, molecular biology, biophysics, and molecular­ genetics techniques in the study of these ubiquitous intrinsic membrane proteins. Molecular-genetics techniques paved the road to the manipulation of the channel­ forming molecules.

Il capitano generale lagrimo per allegrezza e nomino quel capo: Deseado, perehe l'avevamo gia gran tempo desiderato. Antonio Pigafetta Il Primo Viaggo in torno al Mondo I would like to take some poetic license in introducing this volume in a way that seems appropriate for a country, like Chile, that Iooks to the ocean. I believe it was Heisenberg who compared different times in physics with sailing a ship. He said that most of the time we keep our ships in port, or in the protection of a bay. But on a few occasions we go into the open sea, and those occasions are really the great times in theoretical physics, when everything can change. It does not seem totally unwarranted to hope that we are now entering one of those times. In that spirit, I would like to mention a wonderful book, which in English would be called something like Chile, Or a Crazy Geography.

Ion channels allow us to see nature in all its magnificence, to hear a Bach suite, to smell the aroma of grandmother's cooking, and, in this regard, they put us in contact with the external world. These ion channels are protein molecules located in the cell membrane. In complex organisms, cells need to communicate in order to know about their metabolic status and to act in a coordinate manner. The latter is also accomplished by a class of ion channels able to pierce the lipid bilayer membranes of two adjacent cells. These intercellular channels are the functional subunits of gap junctions. Accordingly, the book is divided in two parts: the first part is dedicated to ion channels that look to the external world, and the second part is dedicated to gap junctions found at cell interfaces. This book is based on a series of symposia for a meeting on ion channels and gap junctions held in Santiago, Chile, on November 28-30, 1995. The book should be useful to graduate students taking the first steps in this field as well as a reference for the aficionado. The aim of the meeting was mainly to show the impact of various modern techniques, including cell biology, molecular biology, biophysics, and molecular­ genetics techniques in the study of these ubiquitous intrinsic membrane proteins. Molecular-genetics techniques paved the road to the manipulation of the channel­ forming molecules.

This book is a compilation of articles based on some of the talks given at the Centro de Estudios Cientificos (CECS) in Valdivia during the course of a celebration to th mark the 60 birthdays of Ramon Latorre and Enrico Stefani. Ramon Latorre is one of the most outstanding figures in channel Biophysics today. The first surprise is that he trained as a Biochemist! He soon, however, became a biophysicist through his work with Guayo (Eduardo) Rojas who guided him during his Ph. D thesis in the Laboratorio de Fisiologia Celular in Montemar. His work at N. I. H with Gerald Eherenstein and Harold Lecar constitutes one of the milestones of single ion channel Biophysics. This classical work, done in planar bilayers, set the basis for understanding voltage-dependent conductances with single channel studies and predates, by many years, later studies using patch clamping techniques. Ramon was one of the firsts to find and recognize the importance of calci- activated potassium channels and to begin a detailed study of channel properties. He pioneered the ideas of voltage and calcium modulation of the open probability and he added detailed studies of gating and its modulation by other ions.Ramon is also interested in permeation and selectivity and he produced classical studies on the number of water molecules in the channel and sites occupied by barium. Results and concepts that have recently taken front page as the structure of KcSa has been described.

The 2002 Pan-American Advanced Studies Institute School on Quantum Gravity was held at the Centro de Estudios Cientificos (CECS),Valdivia, Chile, January 4-14, 2002. The school featured lectures by ten speakers, and was attended by nearly 70 students from over 14 countries. A primary goal was to foster interaction and communication between participants from different cultures, both in the layman’s sense of the term and in terms of approaches to quantum gravity. We hope that the links formed by students and the school will persist throughout their professional lives, continuing to promote interaction and the essential exchange of ideas that drives research forward.This volume contains improved and updated versions of the lectures given at the School. It has been prepared both as a reminder for the participants, and so that these pedagogical introductions can be made available to others who were unable to attend. We expect them to serve students of all ages well.

This book is a compilation of articles based on some of the talks given at the Centro de Estudios Cientificos (CECS) in Valdivia during the course of a celebration to th mark the 60 birthdays of Ramon Latorre and Enrico Stefani. Ramon Latorre is one of the most outstanding figures in channel Biophysics today. The first surprise is that he trained as a Biochemist! He soon, however, became a biophysicist through his work with Guayo (Eduardo) Rojas who guided him during his Ph. D thesis in the Laboratorio de Fisiologia Celular in Montemar. His work at N. I. H with Gerald Eherenstein and Harold Lecar constitutes one of the milestones of single ion channel Biophysics. This classical work, done in planar bilayers, set the basis for understanding voltage-dependent conductances with single channel studies and predates, by many years, later studies using patch clamping techniques. Ramon was one of the firsts to find and recognize the importance of calci- activated potassium channels and to begin a detailed study of channel properties. He pioneered the ideas of voltage and calcium modulation of the open probability and he added detailed studies of gating and its modulation by other ions.Ramon is also interested in permeation and selectivity and he produced classical studies on the number of water molecules in the channel and sites occupied by barium. Results and concepts that have recently taken front page as the structure of KcSa has been described.

The 2002 Pan-American Advanced Studies Institute School on Quantum Gravity was held at the Centro de Estudios Cientificos (CECS),Valdivia, Chile, January 4-14, 2002. The school featured lectures by ten speakers, and was attended by nearly 70 students from over 14 countries. A primary goal was to foster interaction and communication between participants from different cultures, both in the layman’s sense of the term and in terms of approaches to quantum gravity. We hope that the links formed by students and the school will persist throughout their professional lives, continuing to promote interaction and the essential exchange of ideas that drives research forward.This volume contains improved and updated versions of the lectures given at the School. It has been prepared both as a reminder for the participants, and so that these pedagogical introductions can be made available to others who were unable to attend. We expect them to serve students of all ages well.

This volume is based on a meeting on Quantum Mechanics of Fundamental Systems, held December 17-20 of 1987, at the Centro de Estudios Cientificos de Santiago (CECS). The meeting was intended to review new developments in the field defined by its purposely vague title. We were especially interested in communicating important advances in a broad perspective and in a self-contained manner to a wide colleague- ship, and in particular to Latin American physicists. Whatever success we may have achieved in that direction would cer- tainly not have been possible without the help and generosity of many people. For their kind support we thank the Tinker Foundation, the Inter- national Centre for Theoretical Physics, the Ministere des Affaires Etrangeres et Service Culturel et de Cooperation Scientifique et Technique de France and the Centro Latinoamericano de Fisica. We are especially grateful to the Santiago College and to its principal, Rebeca Donoso, for allowing us to hold the meeting at that school when, at the last moment, we were deprived of the previously arranged meeting site.Last but not least we thank the participants for an extraordinary week and the CECS staff for performing, as usual, beyond any reasonable expectation.

The almost irresistible beauty of string theory has seduced many theoretical physicists in recent years. Even hardened men have been swept away by what they can already see and by the promise of even more. It would appear fair to say that it is not yet clear what form the theory will finally take and in what precise way it will relate to the physical world. However, it would seem equally fair to state that, most likely, strings are here to stay and will playa profound and central role in our conception of the universe. There is therefore a pressing need to provide both practicing physicists and advanced students with ways to master quickly, but soundly, the basic principles of the theory. The present volume is a step in that direction. It contains a lucid presentation of the basic principles of string theory in forms which may survive future developments. The book is an outgrowth of lectures given by Lars Brink and Marc Henneaux at the Centro de Estudios Cientificos de Santiago. The lectures covered in a self-contained manner different but complementary aspects of the foundations of string theory.

This book was originated from a series of lectures given in a course on the physical properties of biological membranes and their functional implica­ tions. The course was intended to allow students to get acquainted with the physical techniques used to study biological membranes. The experience was valuable and we feel that a detailed description of the procedures used and of various examples of the results obtained allowed many students to become familiar with a theme that is not often part of regular courses on membrane physiology or biophysics. This book is designed as a tutorial guide for graduate students interested in understanding how physical methods can be utilized to study the proper­ ties of biological membranes. It includes first a detailed description of applications of physical techniques-such as X-ray fiber diffraction methods (Chapter 1), 2H and 13C NMR spectroscopy (Chapter 2), and calorimetry (Chapter 3)-in the study of the properties of lipid model membranes. A description of how to measure molecular mobility in membranes (Chapter 4) follows, and the book concludes with three chapters in which biological membranes are the subject of study. Chapter 5 deals with the acetylcholine receptor and its membrane environment; Chapter 6 discusses how fluorescence techniques can be applied in the study of the calcium ATPase of sarcoplasmic reticulum; and Chapter 7 explains how protein­ lipid interactions modulate the function of the sodium and proton pumps.

The majesty of the icefields is beyond description. He who has been fortunate to be there once, remains bound forever. To a theoretical physicist working on black holes the icefields produce a familiar vertigo, the instinctive certainty of being confronted with something so simple and beautifully extreme that it must be of importance. The meeting whose proceedings are contained in this volume was conducted onboard of a vessel that went to the icefields, and the participants could literally set foot on them. It was expected that, for those who had not been there before, this would constitute a ritual of initiation. And so it did. For this reason we like to refer to the meeting as an expedition because, although it did not have the hardship, it had the spirit. After this foundational expedition there have been two others, this time both with spirit and hardship, one from Chile and one from Argentina. At the moment of this writing, a fourth, full-fledged airborne expedition to the icefields is about to depart from Valdivia. Many of the people of many nations who were on board of the Aquiles will take part in it. We look forward to its results, and to an ongoing exciting scientific adventure. Claudio Teitelboim Director, Centro de Estudios Cientfficos Valdivia, September 2001 v ACKNOWLEDGMENTS This volume is the result of the effort and generosity of many people and institutions.

From January 8-13,1990, distinguished physicists from many nations came to Chile to share with each other and with Latin American students exciting recent developments. The occasion was the third of a series of meetings on Quantum Mechanics of Fundamental Systems which are held every two years at the Centro de Estudios Cientificos de Santiago. This volume grew out from that gathering. The meeting was possible thanks to the generous support of the Tinker Foundation, the John D. and Catherine T. MacArthur Foundation, the International Centre for Theoretical Physics, the Ministere des AfIaires Etrangeres et Service Culturel et de Cooperation Scientifique et Technique de France, the Third World Academy of Sciences, and FONDECYT-Chile. The happy winds blowing over Chile at the time enhanced the joy provided by the beauty of the physics discussed. Claudio Teitelboim Jorge Zanelli Santiago, Chile vii Contents Chapter 1 Fractional Statistics in Quantum Mechanics Daniel P. Arovas 1. Introduction...1 2. Charge-Flux Composites...4 3. Dilute Anyon Gases ...6 4. Fractional Statistics in the Quantized Hall Effect ...8 5. Many-Body Theory of the Anyon Gas...16 6.Chern-Simons Field Theory and Fractional Statistics ...20 Appendix: Many Anyons in a Magnetic Field...23 . .

This book is based on a series of lectures for a course on ionic channels held in Santiago, Chile, on November 17-20, 1984. It is intended as a tutorial guide on the properties, function, modulation, and reconstitution of ionic channels, and it should be accessible to graduate students taking their first steps in this field. In the presentation there has been a deliberate emphasis on the spe­ cific methodologies used toward the understanding of the workings and function of channels. Thus, in the first section, we learn to "read" single­ channel records: how to interpret them in the theoretical frame of kinetic models, which information can be extracted from gating currents in re­ lation to the closing and opening processes, and how ion transport through an open channel can be explained in terms of fluctuating energy barriers. The importance of assessing unequivocally the origin and purity of mem­ brane preparations and the use of membrane vesicles and optical tech­ niques in the stUGY of ionic channels are also discussed in this section. The patch-clamp technique has made it possible to study ion channels in a variety of different cells and tissues not amenable to more conven­ tional electrophysiological methods. The second section, therefore, deals with the use of this technique in the characterization of ionic channels in different types of cells, ranging from plant protoplasts to photoreceptors.

The present volume originated from the workshop "Transduction in Biological Sys­ tems," held at the Marine Biological Station of the Universidad de Valparaiso, Mon­ temar, Chile, May 23-30, 1988, and contains contributions from most of the partici­ pants in the workshop. The title of both the workshop and the book reflects accurately the central theme discussed during several days of intense debate and profound intellectual exchange in the peaceful environment offered by the central coast of Chile. It was apparent that the workshop was a great success-a sentiment expressed by many seasoned attendees, some of whom dared opinions as strong as "It was the best ever." There is no single reason to explain why this workshop was so successful. Certainly instrumental was the incredible effort displayed by the Chilean Organizing Committee in selecting adequate facilities and in organizing social events that supplemented the scien­ tific sessions and provided an authentic fraternal environment for the participants. Equally important were the foreign participants, who enthusiastically gave of their time to take part in the event, and the students, who came from Chile as well as from several other Latin American countries, and who applied the necessary pressure in their repeated demands for scientific clarity, accuracy, and sincerity.

Ion channels allow us to see nature in all its magnificence, to hear a Bach suite, to smell the aroma of grandmother's cooking, and, in this regard, they put us in contact with the external world. These ion channels are protein molecules located in the cell membrane. In complex organisms, cells need to communicate in order to know about their metabolic status and to act in a coordinate manner. The latter is also accomplished by a class of ion channels able to pierce the lipid bilayer membranes of two adjacent cells. These intercellular channels are the functional subunits of gap junctions. Accordingly, the book is divided in two parts: the first part is dedicated to ion channels that look to the external world, and the second part is dedicated to gap junctions found at cell interfaces. This book is based on a series of symposia for a meeting on ion channels and gap junctions held in Santiago, Chile, on November 28-30, 1995. The book should be useful to graduate students taking the first steps in this field as well as a reference for the aficionado. The aim of the meeting was mainly to show the impact of various modern techniques, including cell biology, molecular biology, biophysics, and molecular­ genetics techniques in the study of these ubiquitous intrinsic membrane proteins. Molecular-genetics techniques paved the road to the manipulation of the channel­ forming molecules.