computing pI of a phosphoprotein

[Will Fuller]

Hi,

I'm trying to get a rough estimate of the shift I should expect on a 2D gel
when my protein of interest is phosphorylated. It seems to me that the shift
would be bigger for a protein of, say 10kDa, than for one of say 100kDa. Is
this right? I know there are lots of resources available for calculating
theoretical pI's of proteins, but do they also exist for phosphoproteins?

I know there are other variables to consider as well as just the size of a
protein, but I'd just like a rough rule of thumb. Thanks in advance.
Will

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