Morphological analysis of in vitro assembled mutant CAp24 proteins. Mutant and wild type CAp24 proteins were induced for in vitro CAp24 tubular formation (see Fig. 3). At the end of the experiment, the proteins were fixed in freshly prepared 2.5% glutaraldehyde. The electron micrographs show negatively stained thin-sections of the in vitro assembled CAp24 tubular structures used in turbidity assay. Micrographs of the CAp24 mutant D51N (A), D51E (B), D51Q (C) and the wild type CAp24 (D). Bars indicate 100 nm.