Editing 293F Protein Production (section)

==== Cell Culture<br>  ====

1. HEK-293 cells adapted to cultivation in serum-free suspension<br>2. Cylindrical and square-shaped glass bottles with nominal volumes of 100 mL to 5 L<br>3. Ex-cell 293 medium without L-glutamine and phenol red (Sigma-Aldrich).<br>4. 50× L-glutamine and phenol red solution. A stock solution with 200 mM glutamine and 250 g/mL phenol red is made by dissolving 29.23 g/L glutamine&nbsp; and 250 mg phenol red (Sigma-Aldrich) in 800 mL water. After the compounds are dissolved, the volume is adjusted to 1 L by further addition of water. The solution is sterilized by filtration through a 0.2- um Steritop (bottle-top) filter unit&nbsp; with a neck size of 45 mm (Millipore). The solution is transferred into sterile 50-mL centrifuge tubes and kept frozen at −20°C. For each liter of Ex-cell® 293 medium, 20 mL of the stock solution is added.<br>5. Trypan blue solution (0.4%) (Sigma-Aldrich).<br><br>