I have purified PEG modified albumin by ion exchange chromatography. Final product 96KD analyzed on analytical FPLC with >99% purity.
My PEG reagent if 30KD and Albumin is 66 KD, after conjugation the total mass of PEGylated albumin is 96 KD. When I analyzed by MALDI TOF, I observed two peaks, one is 96 KD and the other is 66 KD.
Why the 99 % pure modified protein product shows two peaks ?