• 10 mM KOAc pH 7.0 (10 ml of a 1M stock/L)
• 80 mM CaCl2.2H2O (11.8 g/L)
• 20 mM MnCl2.4H2O (4.0 g/L)
• 10 mM MgCl2.6H2O (2.0 g/L)
• 10% glycerol (100 ml/L)
• Adjust pH DOWN to 6.4 with 0.1N HCl if necessary
• Adjusting pH up will precipitate manganese dioxide from Mn containing solutions.
• Sterile filter and store at 4°C
• Slight dark precipitate appears not to affect its function

Adapted from [http://openwetware.org/wiki/TOP10_chemically_competent_cells OpenWetWare]