polyacrylamide RNA gel - (Jan/23/2013 )

Hello, everyone! I have a big doubt about a recipe for a polyacrylamide gel for RNA... it says "add 5.6 mL of 40% acrylamide (acryl:bis acryl = 19:1) to the gel mix for a 15% polyacrylamide gel". I don't understand what that 40% means if I have the 19:1 relation. Should I put 20g of the 19:1 polyacrylamide mix in 50 ml and then take 5.6 ml of that solution for the gel mix?

The 19:1 is the ratio of acrylamide to bis-acrylamide. The 40% refers to the overall concentration of acrylamide in the solution.

V1C1=V2C2
40*5.6=15*V2
v2=15, so you are making 15 ml of gel solution at 15% acrylamide...

Thanks, but that wasn't my question, I already know that the final volume is 15ml. I'm pretty sure that my guess is right but would feel more secure if sb say so.

do you have a powdered acrylamide/bis mix or is it liquid?

if it is powdered then you are correct, 20gm brought to 50ml with water will give you a 40% solution (of which you take 5.6ml to make 15ml gel solution).

if the mix is liquid then bob1's answer was spot on.

It's powdered, thanks to both!