Modified Barth's Saline for Xenopus (MBS)

Make a 10× MBS stock:

 800 mm NaCl

 10 mm KCl

 10 mm MgSO₄·7H₂O

 50 mm HEPES free acid

 25 mm NaHCO₃

Prepare a 10× stock that consists of the reagents listed above, adjusting the pH to 7.8 with NaOH and sterilizing by autoclaving. Prepare a separate 0.1 m stock of CaCl₂, and sterilize by autoclaving. Store the stocks indefinitely at room temperature.

To make 1× MBS, dilute the 10× MBS stock with type 1 ultrapure water (ASTM International 2018), and add CaCl₂ stock to a final concentration of 0.7 mm.

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