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# Making a solution of antibiotica-Geneticin

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### #1 autumn

autumn

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Posted 30 March 2005 - 10:18 PM

The protocol:

100X G418 (Geneticin): Obtained as crystalline powder from
GIBCO (cat.# 860-1811) and stored @ room temp. in T932.

The amount of active ingredient per total weight
is printed on the bottle label. (This value is generally about
500 mg/mg, active ingredient/total weight).

The 100X stock solution is prepared in PBS to give
a final stock concentration of 18 mg active ingredient per ml.

Procedure:

-- Into a sterile, conical 50 ml tube, weigh an amount of
G418 equal to the quantity required to prepare either 20 or
40 ml of 100X solution.
Example:

You need to prepare 20 ml of 100X G418. The stock G418
powder is 495 mg/mg active ingredient.
Perform the following
conversion to calculate the amount of G418 to weigh out:
- (18 mg active ingredient/ml) x 20 ml = 360 mg active
ingredient required
- (360 mg active) / (0.495 mg active/total weight) = 727 mg
total weight
.

Working in the hood, aseptically add enough PBS to dissolve
the G418, but do not go over the final volume mark (the graduation
marks on the side of the tube are accurate enough for this
determination). The solution will be pale yellow in color (acidic).
Once dissolved, bring to the desired volume with PBS.

My question:
How do they get; (360 mg active) / (0.495 mg active/total weight) = 727 mg total weight from the stock G418 powder is 495 mg/mg active ingredient? And what mass of Geneticin should i add to 20ml solvent? Is that 360mg or 727mg Geneticin?

Thanks.

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