I'm trying to measure the efficiency and optimise the primer concentration for my assay which is measuring TBP expression. I'm doing this with a standard curve of cDNA with the points: 100ng, 10ng, 1ng, 0.1ng, 0.001ng per rxn.

The problem is that TBP is expressed quite low in most cells usually late 20s early 30s in CP/CT. So in the above standard curve, I detect the first two points of the curve okay but the rest aren't detected.

How do other people optimise their low abundant assays?

Maybe I should just start my standard curve at a higher concentration like 500ng or maybe add more points by using a 1/2 log dilution?