Provided are processes and materials for solving biological or structural information about proteins or other organic molecules. The processes capitalize on a rigid multimeric nanocage formed from self-assembling substructure proteins. The processes and materials allow for recognition and tight, optionally covalent, bonding of any protein molecule with a tag complementary to a capture sequence on the nanocage. The processes and materials may be used to obtain biological or structural information by cryo-electron microscopy and overcome prior limitations of target protein size or salt concentration.