cDNA of the open reading frame of rat a 1 -antitrypsin (Gene Bank Accession Number NM_022519) (a kind gift from Dr. G. Thomas, Vollum Institute, Oregon Health & Science University, Portland, USA) was inserted into pSG5 and used as a template to generate S1P-specific a 1 -antitrypsin variants by recombinant polymerase chain reaction (PCR) using overlapping oligonucleotides [43] . The sequences of the oligonucleotides used are listed in Table S1 . The resulting full-length PCR products were digested