PEG

[chenlong at BIO.CORNELL.EDU]

Hi,

Can someone tell me some physical and chemical properties of polyethylene glycol 
4000? I mixed it with a protein at pH4.8 (at this pH this protein is slightly 
positively charged. Its isoelectric point is 5.4). I want to know sth like the 
charges of PEG at this pH. Can PEG complex with the protein? If they form 
complex,what force plays the big role? Wan der waals? H-bonding? electrostatics? 
chemical cross-linking by itself or with protein? If concentration of PEG too 
high, protein crystal dies. What did PEG do to protein and/or protein crystal 
and how to avert it? thank you.

Chenlong Li.