An analytical assessment shows a preferential distribution of three space groups, i.e. P2₁2₁2₁ > P12₁1 > C121, in soluble and membrane proteins as well as in their complexes. The distribution of these space groups also shows the same pattern whether a protein crystallizes with a monomer or an oligomer in the asymmetric unit. The results also indicate that the sizes of the two entities in the structures of soluble proteins crystallized as complexes do not influence the frequency distribution of space groups.

A human V_H fragment derived from the single-chain antibody scFvM12 has been crystallized and characterized at 1.8 Å resolution by X-ray diffraction.