Insulin (0.5 mg/mL)
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1. Working under a sterile tissue culture hood, pre-rinse a 0.22-µm filter with sterile H2O. Discard the flowthrough.
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2. Add 50 mg of insulin (either recombinant human insulin [Sigma-Aldrich I2643] or bovine pancreas insulin [Sigma-Aldrich I6634]) to 100 mL of sterile H2O in a 200-mL beaker. Immediately add 500 µL of 1 n HCl to adjust the pH.
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3. Stir the mixture with a sterile pipette to dissolve the insulin completely; avoid creating bubbles.
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4. Filter the solution through the prerinsed 0.22-µm filter.
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5. Make 5-mL aliquots and store at 4°C for up to 4–6 wk. For use in media, dilute 100× to a concentration of 5 µg/mL.
- © 2014 Cold Spring Harbor Laboratory Press
