What is a protein crystal? Can we apply the terminology of classical industrial crystallization to them?

The nature of protein crystals is discussed. Since protein crystals contain not only proteins but also other substances the usage of conventional terms (of industrial crystallization) of naming such crystals is questioned. The proof that there are other components than the protein itself in a protein crystal is given. It is suggested to use a procedure like in biotechnology to guarantee the production of the right protein crystals according to...