Herein is reported a polypeptide comprising a first polypeptide and a second polypeptide each comprising in N-terminal to C-terminal direction at least a portion of an immunoglobulin hinge region, which comprises one or more cysteine residues, an immunoglobulin CH2-domain and an immunoglobulin CH3-domain, wherein i) the first polypeptide comprises the mutations 1253A, H310A and H435A and the second polypeptide comprises the mutations H310A, H433A and Y436A, or ii) the first polypeptide comprises the mutations 1253A, H310A and H435A and the second polypeptide comprises the mutations L251D, L314D and L432D, or iii) the first polypeptide comprises the mutations 1253A, H310A and H435A and the second polypeptide comprises the mutations L251S, L314S and L432S.
