by
JMB » Fri Jun 12, 2020 5:38 pm
These data imply a heterogeneous product, with possibly three sets of compounds.
Looking at the mass differences, I would suspect incomplete de-glycosylation together with a series of phosphoric / sulfuric acid adducts.
Further treatment with the PNGase and/or a phosphatase or sulfa tase might help to confirm, or not, this speculation.
I am aware that H3PO4 / H2SO4 adduct s or esters will cause different mass shifts.
Is it possible that the reduction gives the expected homogeneous, sharp peak because the lower MW substances are—-no , the higher MW impurities would be retained by ultrafiltration/ dialysis.
Some years since I have been around this type of problem!
What are your thoughts?
Regards,
JMB