BSA assay and Fluorometric peptide assay do not work for the quantification of the Pepstatin A (aspartic protease/cathepsin D inhibitor/peptide). Does anybody have an idea to quantify it besides using LC-MS?
Somewhat less complicated than LC_MS I would suggest reversed-phase LC in combination with UV detection at 218 nm employing a proper (thus not to steep!) acetonitril gradient using 0,1% TFA.
Thank you Dr. Kees Olieman. I am working on water and ACN with 0.1% TFA at 220nm. I will also check on your recommended wavelength. Thank you once again.