Fixative B for Drosophila Embryos

1% OsO₄ (osmium tetroxide)

0.1 m sodium cacodylate buffer (pH 7.4)

0.2 m sucrose

Prepare by mixing 1 mL of 4% OsO₄, 1 mL of H₂O, and 2 mL of 0.2 m sodium cacodylate buffer. Add sucrose to 0.2 m.

• OsO₄ is available as crystals or 4% aqueous solution in sealed ampules. The 4% solution is more convenient, as the crystals normally take overnight to go into solution.

• © 2012 Cold Spring Harbor Laboratory Press