CXCL12 and Patent ductus arteriosus: Since this unusual form of CXCL12 required SDS for solubilization, and its apparent molecular weight was similar to a putative complex with KRT19, we subjected the SDS eluate from a PDA surgical specimen to immunoprecipitation (IP) with anti-CXCL12 antibody and analyzed the coprecipitated proteins by immunoblotting with anti-KRT19 antibody.