Kynurenate Magnesium Solution

10 mM sodium kynurenate and 100 mM magnesium chloride.

STERILE after filtration

Mixing container: 250 ml flask
Storage container: Exactly 10 ml per tube in ten 13 ml tubes, and 5 ml per tube in twenty 7 ml tubes, labeled "K10 Mg 100" stored in a plastic box in the -20 °C freezer.

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 µm 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.