The pET25b (+) vectors encoding genes for ELPs or FKBP-ELPs were transfected into BLR (DE3) E. coli competent cells (69053, EMD Millipore) and plated onto agar with 100 µg/mL ampicillin. A single colony was inoculated in 50 mL autoclaved terrific broth (TB) media (12105, Mo Bio Laboratories, Carlsbad, CA) supplemented with 100 µg/mL carbenicillin and grown overnight at 37 ºC in a shaker incubator. Starter cultures were then amplified in 3-4 L batches supplemented with 100 µg/mL carbenicillin and allowed to grow for 24 h at 37 ºC. Cell lysis was performed as previously described 58 (link) and protein purification was performed using Inverse Transition Cycling 59 . Purified protein in Dulbecco's sterile PBS buffer (PBL01, Caisson labs, Smithfield, UT) was filtered using 200 nm sterile Acrodisc® 25 mm filters (PN 4612, Pall Corporation, Port Washington, NY) and assayed for concentration using Beer Lambert's law:
where M is molar concentration, A280 and A350 are absorbance at 280 and 350 nm respectively, l is the path length (cm) and MEC is the estimated molar extinction coefficient at 280 nm: 1285 M-1cm-1 for plain ELPs; 11585 M-1cm-1 for FA and FSI; and 20190 M-1cm-1 for FAF 60 (link). Final yields obtained were 50-60 mg/L.
where M is molar concentration, A280 and A350 are absorbance at 280 and 350 nm respectively, l is the path length (cm) and MEC is the estimated molar extinction coefficient at 280 nm: 1285 M-1cm-1 for plain ELPs; 11585 M-1cm-1 for FA and FSI; and 20190 M-1cm-1 for FAF 60 (link). Final yields obtained were 50-60 mg/L.
