gel filtration of glycoproteins

[stoffel at biols.susx.ac.uk]

Hello all,

Following problem:
I've got a protein of about 40 kD (according to its amino acid-sequence) which is glycosylated, when I pass it on a gel filtration column it gives me a very broad and flat peak (well, probably one wouldn't call it a "peak" anymore) somewhere in the range between 70 and 100 kD.  

Question:
If you look at a glycosylated protein in general, would you expect such a behaviour or should it still run as a discret peak? How much does the glycosylation affect the apparent MW of a protein when doing size exclusion, is it likely to increase the size by a factor of 2 or 3, or is this more a hint for dimerisation?

Any comment on this matter (preferably based on personal experience) would be very helpfull 

Thanks a lot,

Christoph

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