Stock solution of Activin A (50 μg/mL)

Reagent	Final concentration (μg/mL)	Amount
Activin A	50	50 μg
Sterile HCl (4 mM)	N/A	1,000 μL
Total	50	1,000 μL

Make 20–50 μL working aliquots and store at −20°C, use within 6 months. Avoid repeated freezing and thawing cycles.