Hello, everyone!!
I've included a general question above, and the answer is yes. However, I am discussing SP3 approaches. I've noticed that several authors haven't discussed peptide recovery using the BCA peptide test following BSA digestion. I'm curious why they just report the numbers of proteins and peptides from MS data rather than the amount of protein and peptides. Can we estimate the amount of digested peptides? Best,
There are two simple rules in this context: 1. you should calibrate your test with exactly the same compound that you want to measure. 2. your matrix should be very similar to the calibration solution. MS is only able to quantify peptides if you either calibrate externally with the same, pure peptides or quantify with isotopically labeled peptides.
As Michael G. Weller indicated, BCA requires a standard curve using a pure sample of the exact analyte you want to quantitate, presented in the exact same matrix (buffer, etc.). Otherwise you easily may be off by a factor of 2.
If you don't really care, and you perform your assay very carefully (time & temp are critical), this systematic error can be reproducible. Prove this and you may report routine results as BCA (OD) rather than peptide ug.
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