Kynurenate Magnesium Solution

10 mM sodium kynurenate and 100 mM magnesium chloride.

STERILE after filtration

Kynurenic acid: Sigma K-3375
MW anhydrous = 189.16.
WARNING: Some batches have water of hydration; this will change the calculations.
If anhydrous, 10 mM = (0.01) (189.16) mg/ml = 1.89 mg/ml = 378 mg/200 ml

Magnesium chloride 4.9 M: Sigma 104-20
Need a 49 times dilution of the 4.9 mM solution, so 200 / 49 = 4.08 ml.

INGREDIENT      Amount for 200 ml of final solution
     
Kynurenic acid    378 mg (if anhydrous)
NaOH 0.3 M   6.67 ml
Sodium phenol red    0.1 ml
Sodium HEPES 500 mM    2.0 ml
Magnesium chloride 4.9 M   4.08 ml
Autoclaved water    Fill to 200 ml

    It is difficult to dissolve the kynurenate. The solution is typically left in the refrigerator for several days, shaking it once or twice a day. Typically, a tiny amount of the solid fails to dissolve.

    The kynurenate solution must be filtered with a pre-washed 0.2 m nylon filter to remove un-dissolved material and bacteria. The large diameter filter sets are used for 200 ml quantities.

    The tubes are then aliquoted and frozen at -20 while being held upright in paper containers. Once the solution has frozen, the tubes can be placed horizontally in the appropriate plastic container in the -20 freezer.

Copyright 2002 Dr. Michael M. Segal, Department of Neurosurgery, Brigham & Women's Hospital, Boston MA 02115, USA.  Many of the solutions are based on recipes from the Furshpan and Potter labs; the recipes given here are the versions we use now in the Segal lab.  Individual copies may be made of this page for use in educational institutions.