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 the first, the second, or the first and the second polypeptide comprise the mutation Y436A (numbering according to the EU index).
