unexpected molecular weight

[fantola]

Hi,
My bands appear at a high molecular weight than expected. I've checked reducing agent concentration, gel % , unespecific binding and many other factors but no matter what I do my samples always appear at higher molecular weight than expected. Anyone has ever had this problem?

[kmunson779]

1) Are you in a system that allows for posttranslational modifications? Have you investigated this possibility?

2) Many proteins' apparent molecular weight by SDS-PAGE does not correlate closely with their calculated mass. Try, for example, a Google search on "anomalous molecular weight by SDS-PAGE" (without quotes) -- you'll pull up quite a few articles investigating this phenomenon.

If you're sure that what you're detecting is what you're supposed to be detecting, I wouldn't worry too much about a small difference in apparent mass, but it would be interesting to see if posttranslational modification could account for the difference.