  Understanding protein self-assembly is important for many biological and
industrial processes. Proteins can self-assemble into crystals, filaments,
gels, and other amorphous aggregates. The final forms include virus capsids and
condensed phases associated with diseases, such as amyloid fibrils. Although
seemingly different, these assemblies all originate from fundamental protein
interactions and are driven by similar thermodynamic and kinetic factors. Here
we review recent advances in understanding protein self-assembly through a soft
condensed matter perspective with an emphasis on three specific systems:
globular proteins, viruses and amyloid fibers. We conclude with a discussion of
unanswered questions in the field.
