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# making G418

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### #1 SF_HK

SF_HK

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Posted 09 April 2009 - 12:22 AM

HI,

I'm not sure about my calculations.

I need to treat my cells with 500ug/ml of G418. HOwever, I'm not sure how to make this. The bottle says 736ug/mg?

### #2 klinmed

klinmed

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Posted 09 April 2009 - 03:26 AM

HI,

I'm not sure about my calculations.

I need to treat my cells with 500ug/ml of G418. HOwever, I'm not sure how to make this. The bottle says 736ug/mg?

When G418 is produced it is not 100% active. The manufacturers determine the active fraction by bioassay. Your powder contains 736/1000 x 100 = 73.6% active G418.

If you want to make a 50 mg/ml stock solution of ACTIVE G418 you therefore need to weigh out 1000/736 x 50= 67.93 mg of G418 for each ml of stock solution. I usually make this x100 stock in a buffer (100 mM HEPES pH 7.3), but many people use PBS. It should be filter-sterilized and stored frozen in aliquots.

It is wise to determine the concentration of drug that works optimally in your system. This is easily done by performing a kill curve.

Hope this helps.

### #3 chromatin

chromatin

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Posted 09 April 2009 - 05:06 AM

HI,

I'm not sure about my calculations.

I need to treat my cells with 500ug/ml of G418. HOwever, I'm not sure how to make this. The bottle says 736ug/mg?

Here is recipe for you:
http://www.bioprotocols.info/model_organisms/Yeast/media/geneticin-media-plates.php