D in 25 ml of lysis buffer (50 mM Tris, pH 8, 2 mM EDTA, 0.5 Triton X-100 with the addition of Complete Mini Protease Inhibitor Tablets (Roche)). Mechanical disruption was used to lyse the cells (i.e. French Press or sonication) and the inclusion bodies isolated from the cell supernatant by centrifugation at 180006g at 2?uC for 20 minutes. The inclusion body pellet was solubilized in resuspension buffer (50 mM Tris, pH 8, 6 M GuHCl (Sigma, G4505), 10 mM DTT) by repeatedly passing the inclusion bodies through an 18g syringe. It is worth noting that any insoluble material can be centrifuged out at this time at 180006g at 2?uC for 20 minutes. The resuspended protein material was then diluted 50 in dialysis buffer #1 (50 mM Tris, pH 8, 2 M GuHCl) resulting in a 4 M GuHCl containing solution. The protein solution was then dialyzed overnight at 4uC in snakeskin dialysis tubing (Pierce) against 2 L of buffer #1. The following day the dialysis buffer was changed to 2 L of dialysis buffer #2 (50 mM Tris, pH 8, 1 M GuHCl, 0.4 M Arginine (Sigma, A5006), 3 mM Reduced Glutathione, 0.9 mM Oxidized Glutathione) for overnight dialysis at 4uC. The following day the dialysis buffer was diluted 50 with water and dialysis continued overnight. Any insoluble material was centrifuged (180006g at 2?uC for 20 minutes) and the remaining protein solution dialyzed overnight at 4uC against 1 L of dialysis buffer #3 (50 mM Tris, pH 8, 250 mM NaCl, 0.1 M Arginine, 3 mM Reduced Glutathione, 0.9 mM Oxidized Glutathione) to remove the remaining GuHCl.Bioactivity AssayThe rhGM-CSF bioactivity was analyzed with a proliferation assay using TF-1 1480666 cells [22]. The TF-1 cells (ATCC number CRL-2003) were maintained in RPMI medium supplemented with 10 fetal bovine serum (FBS), L-glutamine, sodium pyruvate, and penicillin/streptomycin (all from Gibco) with 2 gibbon IL-3 added just prior to use. The cells were grown in a 37uC humidified incubator with 5 CO2. Commercial rhGM-CSF was obtained from ImmunoTools (cat # 11473127, lyophilized), reconstituted, aliquoted and stored at 280uC. For the proliferation assay, TF-1 cells were washed 5 times in RPMI with no supplements and seeded 1000 cells per 24272870 well in growth medium with no IL-3 or rhGM-CSF in 96 well SMER 28 biological activity tissue culture plates (BD Falcon # 353072). rhGM-CSF was serially diluted two-fold in growth medium and added to the washed cells to give final concentrations ranging from 12.8 ng/mL to 1.56 pg/ mL, and 100 mL total volume per well. Control wells containing cells but no rhGM-CSF (blank) and rhGM-CSF with no cells were performed. The plates were incubated in a 37uC humidified incubator with 5 CO2 for 4 days. Cell Proliferation Reagent WST-1 (Roche cat # 11 644 807 001) was added and incubation continued as above for 4 hrs. The absorbance values at wavelength 450 nm, with reference wavelength of 690 nm values subtracted, were determined using a plate reader (Molecular Devices). The absorbance values were directly proportional to the number of viable cells because the 301353-96-8 web tetrazolium salts in the WST-1 reagent were cleaved to formazan by mitochondrial dehydrogenases in the cells. The blank values were subtracted from all wells on each plate and the values plotted. Unit values were defined as 50 U/mL being equivalent to the concentration of GMCSF that supports 50 of maximal growth under the assay conditions used.rhGM-CSF PurificationThe final dialyzed protein solution was clarified by centrifugation (180006g at 2?uC for 20 minutes) an.D in 25 ml of lysis buffer (50 mM Tris, pH 8, 2 mM EDTA, 0.5 Triton X-100 with the addition of Complete Mini Protease Inhibitor Tablets (Roche)). Mechanical disruption was used to lyse the cells (i.e. French Press or sonication) and the inclusion bodies isolated from the cell supernatant by centrifugation at 180006g at 2?uC for 20 minutes. The inclusion body pellet was solubilized in resuspension buffer (50 mM Tris, pH 8, 6 M GuHCl (Sigma, G4505), 10 mM DTT) by repeatedly passing the inclusion bodies through an 18g syringe. It is worth noting that any insoluble material can be centrifuged out at this time at 180006g at 2?uC for 20 minutes. The resuspended protein material was then diluted 50 in dialysis buffer #1 (50 mM Tris, pH 8, 2 M GuHCl) resulting in a 4 M GuHCl containing solution. The protein solution was then dialyzed overnight at 4uC in snakeskin dialysis tubing (Pierce) against 2 L of buffer #1. The following day the dialysis buffer was changed to 2 L of dialysis buffer #2 (50 mM Tris, pH 8, 1 M GuHCl, 0.4 M Arginine (Sigma, A5006), 3 mM Reduced Glutathione, 0.9 mM Oxidized Glutathione) for overnight dialysis at 4uC. The following day the dialysis buffer was diluted 50 with water and dialysis continued overnight. Any insoluble material was centrifuged (180006g at 2?uC for 20 minutes) and the remaining protein solution dialyzed overnight at 4uC against 1 L of dialysis buffer #3 (50 mM Tris, pH 8, 250 mM NaCl, 0.1 M Arginine, 3 mM Reduced Glutathione, 0.9 mM Oxidized Glutathione) to remove the remaining GuHCl.Bioactivity AssayThe rhGM-CSF bioactivity was analyzed with a proliferation assay using TF-1 1480666 cells [22]. The TF-1 cells (ATCC number CRL-2003) were maintained in RPMI medium supplemented with 10 fetal bovine serum (FBS), L-glutamine, sodium pyruvate, and penicillin/streptomycin (all from Gibco) with 2 gibbon IL-3 added just prior to use. The cells were grown in a 37uC humidified incubator with 5 CO2. Commercial rhGM-CSF was obtained from ImmunoTools (cat # 11473127, lyophilized), reconstituted, aliquoted and stored at 280uC. For the proliferation assay, TF-1 cells were washed 5 times in RPMI with no supplements and seeded 1000 cells per 24272870 well in growth medium with no IL-3 or rhGM-CSF in 96 well tissue culture plates (BD Falcon # 353072). rhGM-CSF was serially diluted two-fold in growth medium and added to the washed cells to give final concentrations ranging from 12.8 ng/mL to 1.56 pg/ mL, and 100 mL total volume per well. Control wells containing cells but no rhGM-CSF (blank) and rhGM-CSF with no cells were performed. The plates were incubated in a 37uC humidified incubator with 5 CO2 for 4 days. Cell Proliferation Reagent WST-1 (Roche cat # 11 644 807 001) was added and incubation continued as above for 4 hrs. The absorbance values at wavelength 450 nm, with reference wavelength of 690 nm values subtracted, were determined using a plate reader (Molecular Devices). The absorbance values were directly proportional to the number of viable cells because the tetrazolium salts in the WST-1 reagent were cleaved to formazan by mitochondrial dehydrogenases in the cells. The blank values were subtracted from all wells on each plate and the values plotted. Unit values were defined as 50 U/mL being equivalent to the concentration of GMCSF that supports 50 of maximal growth under the assay conditions used.rhGM-CSF PurificationThe final dialyzed protein solution was clarified by centrifugation (180006g at 2?uC for 20 minutes) an.