First, find the concentration of our protein stock. ug/ul would be best suited. Then determine how much amount of protein you want to load. If you are running an SDS page then 20ug to 40ug would be more than sufficient. Now, if your protein concentration in 1ug/ul then to load 20 ug of total protein, you have to add 20ug/1(ug/ul) = 20ul (from the protein stock)

You also need to consider the complexity of the protein sample. If you have a pure protein you won’t need 20-40ug, it’ll be a tenth as much. For a complex mixture eg cell lysate or cell supernatant, the proteins will be distributed across the whole vertical dimension of the gel, hence you need more micrograms to see the individual bands clearly.

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Sourav Ghosh thankue

but how to find out the protein conc. of stock if its diluted and only 10ul of that sample is used for Quatification.

Normally if you use bradford colorimertric method to estimate proteins, then it is sensitive enough to atleast detect 0.05ug/ul concentration. I use 5ul of protein sample for bradford. if you can elaborate more on your sample or nature of your sample, then i can suggest better.

I use 10ul of protein sample (cell lysate) for bradford.