We have previously expressed and purified the extracellular segment spanning positions 1-275 of the human HLA-A*11:01 in a denatured and pre-oxidized version that rapidly refold and bind appropriate target peptides (Ostergaard et al. 2001; Ferre et al. 2003) . Codon-optimized genes encoding the corresponding segments of SLA-1*0401 (α 1 α 2 ) and SLA-1*0401 (α 3 ) were constructed as described in the "Materials and methods" section and used to replace the HLA-A*11:01 gene segment in the above construct generating a new construct allowing for the expression of SLA-1*0401. For the generation of HLA-A*11:01/SLA-1*0401 chimeras, the genes encoding α 1 (spanning positions 1-90), α 2 (spanning positions 91-181), and/or α 3 (spanning positions 182-275) domains of HLA-A*11:01 and SLA-1*0401 were exchanged using Seam-Less and touch-down cloning strategies. Genes encoding the extracellular segments 1-275 of the above natural or chimeric MHC-I molecules were C-terminally fused to a biotinylation tag (as indicated for SLA-1*0401 in Online Resource 1), inserted into pET28, and expressed in inclusion bodies in E. coli (Fig. 2 shows SDS-PAGE of lysates of recombinant E. coli before and 3 h after IPTG induction). The fusion proteins were extracted into 8 M urea (without any reducing agents), purified by ion exchange, hydrophobic and gel filtration chromatography (all conducted in 8 M urea, without any reducing agents) (Fig. 3 shows SDS-PAGE of the purified SLA-1*0401 after gel filtration), concentrated, and stored in urea at −20°C.