Reason for diffs. in mol wgt/ pI

LOGAND logand at
Fri Apr 28 12:29:10 EST 1995

Dear All,

This question may be best answered by "protein-netters" but I'll give 
"M&Ms" the first shot.

Where could I find information and preferably examples demonstrating the 
need for caution when quoting polypeptide mol. weights and pIs from 
SDS-PAGE gels. That is, confirmation of the nature of measurements by this 
method as 'apparent'.

What I want to know is to what extent small changes in primary structure 
can change the apparent pI and mol. weight by large values. Will 
glycosylation change both? Basically am I right to be very cautious in 
making any decisions about the similarity/disimilarity of two polypeptides 
which differ in both pI and size. Is an apparent change in mobility 
calculated as 4kDa easily accounted for?

Thanks for your help.

David C. Logan

Logand at  

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