A major part of my lab investigations is running radioactive 2-DG assays to measure glucose uptake of L6.GLUT4myc myotubes under various conditions. For the insulin stimulation at 100 nM, I have been told to make the insulin fresh, so I make a 200 uM stock solution dissolving the powder in 0.005N HCl. I then dilute the solution to 1 uM before aliquoting directly into my cells for 100 nM insulin spike for 20 minutes. An issue I have been facing is to achieve 200 uM i'm weighing around 0.0001 - 0.0010 grams, which can vary as our scale is not great at minutely detecting the changes. I was just wondering if I take a 50 mg insulin powder, make a 200 uM stock solution to aliquot and store at 2-8C if that can be used for my 2-DG assays and if so, how long can it be stored for?