UAS sequences (from pValium10-roe) drive expression of a polypeptide that encodes a single-chain trimer of collagen IV NC1 domains, that are from the vkg, Col4a1 and vkg genes respectively. The NC1 domains are joined by flexible 7-residue GSSASSG linkers and a mEmerald tag is present at the C-terminal end of the coding sequence (again, joined to the last NC1 domain by a GSSASSG linker).