ABSTRACT
It is hard to overestimate the importance of electrostatic interactions associated with charged objects in soft and biological matter. In aqueous environments, typical to many of these systems, charges tend to dissociate and affect a wealth of functional, structural and dynamical properties. Without attempting to enumerate an exhaustive list, we mention a few examples. Polymers are exible and elongated one-dimensional objects (see, e.g., chapters by Warren, Podgornik, MacKintosh and Bensimon in this volume). In aqueous solutions they often carry charges, like the naturally occurring DNA or synthetic polyelectrolytes such as polystyrene sulfonate. The charges on the polymer chain and the counter-ions in solution have an important effect on the rigidity of such chains and on inter-and intra-chain interactions leading to interesting phenomena of aggregation and condensation, as is seen most often in the presence of multivalent counter-ions. The process whereby polyelectrolyte chains migrate in external electric elds is called electrophoresis and is another important phenomena with many applications. Other charged structures are biological cell membranes (see, e.g., chapters by Kozlov and Olmsted in this volume). These soft and uctuating two-dimensional objects are naturally built out of mixtures of phospholipids with or without net charge. Finally, we mention globular proteins with charge groups on their surface (chapter by Elber in this volume), selfassembly of micelles made of charged amphiphiles (chapter by Olmsted in this volume) and charged colloidal particles (see the chapter by Frenkel in this volume) where the charges play a role in stabilising suspensions.
