Urgent Help Needed with Concentration Calculation !!! - Urgent Help Needed with Concentration Calculation !!! (May/25/2009 )

I need to add 2ng/ml of Compound A to 500ml medium.

Compound A is orinially provided at 10ug. As per the data sheet, it needs to be reconstituted to 100ug/ml before diluting to other solutions.

So how to dilute the 10ug Compound A to 100ug/ml ?
And how much of 100ug/ml of Compound A should I add to 500ml medium to obtain 2ng/ml??

Thanks a load for your help

1. Dissolve 10 ug compound A in 100 ul water or whatever solvent to make a 100 ug/ml Solution A

2. Assume that you need to add x ul of solution A you just made, then x * 100ug/ml = 0.002 ug/ml * 500 ml, X=0.01 ml = 10 ul.

So you need to add 10 ul of solution A to 500 ml medium to make a concentration of 2 ng/ml.