This volume is the third of a series on Membrane Proteins and, like the pre­ ceding manuals, is the result of an International Advanced Course entitled Isolation and Characterization of Membrane Proteins: Biochemical and Bio­ physical Aspects sponsored by the Federation of European Biochemical So­ cieties (FEBS) and the Italian Research Council (CNR). The success of the course and the continuous development in the field of membrane biology has prompted me to publish also in this case the protocols of the experiments which were carried out by the students. The students have been able not only to perform the experiments pub­ lished in this manual without help from the instructors, but also to suggest improvements, which have been incorporated in the published version. Care has been taken in making the planning and the execution of the ex­ periments as simple as possible, by listing in detail all the necessary pieces of equipment, test tubes, pipettes, chemicals, etc. At the same time the intro­ duction and the "philosophy" have been limited to the essential, as also the references, only those having been listed which may help in a better under­ standing of the principles and of the biological background of a given experi­ ment.