Size of expressed Protein - (Nov/13/2008 )

Hi, i need help and explanation that can help me solve my problem. I'm working on protein (putative) which i don't know the exact size. the info i have is the size of this gene 840bp so estimated size for protein is around 27kD. I already expressed the protein and after purification i got a prominent size of around 37kD on SDS-page. so anybody can give me any suggestion or comment or whatever to help me. estimated pI is 5.54.
i already check the plasmid through digestion, PCR and sequencing. I've got the expected results for those test. please help me.

thank you in advance.

you can test your protein on size exclusive chromatography, some protein have differrent apparent molecular weight on SDS-PAGE than the theoretic size

hi 'knightxiao' ,

thanks for your suggestion. but can you please explain to me why is this happened. when u said that 'some protein have differrent apparent molecular weight on SDS-PAGE than the theoretic size'.

someone had told me maybe it has something to do with the pI of this protein is 5.54. because of the asidic so it's effect the size that i got. is it true?

Thanks again.