Proteins, sophisticated biological macromolecules, are being expected to use a wide variety of applications in the fields of industry, drug discovery and so on. However, it is now limited due to their structural instability. We first achieved to enclose the protein ubiquitin within the precisely-structured artificial capsules utilizing self-assembly process. This molecule is quite stable in various physicochemical environments. Moreover, to prove the existence of the flexible protein structure within the capsule, we developed a crystallographic method using histogram analysis of MEM electron-density（H-MED）. This method might be useful to identify flexible structures which are difficult to construct atomic models.
