Voltage-gated ion channels are membrane proteins that play a central role in the propagation and transduction of cellular signals (Hille, 1992). Calcium ions entering cells through voltage-gated calcium channels serve as the trigger for neurotransmitter release, muscle contraction, and the release of hormones. Voltage-gated sodium channels initiate the nerve action potential and provide for its rapid propagation because the ion fluxes through these channels regeneratively cause more channels to open.

The viruses have been an attractive model for the study of basic mechanisms of protein/protein and protein/nucleic acid interactions involved in the assembly of macromolecular aggregates. This has been due primarily to their relative genetic simplicity as compared to their structural and functional complexity. Although most of the initial studies were carried out on bacterial and plant viruses, increasing data has also been accumulated from animal viruses, which has led to an understanding of some basic principles, as well as to many specific strategies in every system. The study of virus assembly has been a source of ideas that underlie our present knowledge of the organization of biological systems. It has also provided, since the production of bacteriophage mutants which have allowed the study of assembly intermediates, the first system in which the genetic studies played a dominant role. The increasing volume of data over the last years has revealed how the structural components can interact sequentially through an ordered pathway to yield macromolecular assemblies that satisfy the demands of stability required for a successful transfer of genetic information from host to host.

Intracellular calcium plays an essential role in the transduction of most hormonal, neuronal, visual, and muscle stimuli. (Recent reviews include Putney, 1993; Berridge, 1993a,b; Tsunoda, 1993; Gnegy, 1993; Bachs et al. 1992; Hanson & Schulman, 1992; Villereal & Byron, 1992; Premack & Gardner, 1992; Means et al. 1991).

The adsorption of proteins at the solid-liquid interface is a process of fundamental importance in nature. Extensive reviews (MacRitchie, 1978; Andrade & Hlady, 1986; Norde, 1986) testify to the strong interest which has been shown in the problem during the past few decades. Norde & Lyklema (1978) have rightly pointed out that protein adsorption is scientifically intriguing; the phenomenology is complicated and includes many presently apparently irreconcilable observations.

Biological neural networks are large systems of complex elements interacting through a complex array of connexions. Individual neurons express a large number of active conductances (Connors et al. 1982; Adams & Gavin, 1986; Llinás, 1988; McCormick, 1990; Hille, 1992) and exhibit a wide variety of dynamic behaviours on time scales ranging from milliseconds to many minutes (Llinás, 1988; Harris-Warrick & Marder, 1991; Churchland & Sejnowski, 1992; Turrigiano et al. 1994).

The membrane-spanning portions of many integral membrane proteins consist of one or a number of transmembrane α-helices, which are expected to be independently stable on thermodynamic grounds. Side-by-side interactions between these transmembrane α-helices are important in the folding and assembly of such integral membrane proteins and their complexes. In considering the contribution of these helix–helix interactions to membrane protein folding and oligomerization, a distinction between the energetics and specificity should be recognized. A number of contributions to the energetics of transmembrane helix association within the lipid bilayer will be relatively non-specific, including those resulting from charge–charge interactions and lipid–packing effects. Specificity (and part of the energy) in transmembrane α-helix association, however, appears to rely mainly upon a detailed stereochemical fit between sets of dynamically accessible states of particular helices. In some cases, these interactions are mediated in part by prosthetic groups.

When Hodgkin & Huxley (1952) first embarked on the analysis of their voltageclamp data on the ionic currents in the squid giant axon, they hoped to be able to deduce a mechanism from it, but it soon became clear that the electrical data would by themselves yield only very general information about the class of system likely to be involved.

Drug design means many things to many people. Commercially the aim is the development of compounds that can be patented and meet a variety of regulatory standards. In drug design, for medical purposes, toxicity and bio-availability are major considerations.