Based on Size exclusion chromatography, my protein is a dimer. However, after solving the crystal structure, there was only one monomer. Is there a specific reason for that.
Dear Sherif
your result is strange because generally crystallization is performed at concentration higher than SEC and is more usual observe the opposite.
just some questions:
did you run the Sec in a buffer with similar properties respect that tha cristallizzazion buffer? eg ph, salt and buffering agent?
from the structure is it your protein globular and compact or in open conformation? because expecially if your protein ad low mw and it is shape in not spheric but more asimmetric is possible that also if is mw is monomeric in the SEC his hydrodinamic radius is higher and it will run as a protein with higher mw.
ciao
Manuele
and which Sec coloumn did you used to chech the aggregation state ?
Hi Sherif,
I have also encountered heterodimer in which only one of the proteins forms crystals during crystal growth and I speculate that one of the proteins may be in a bad state and there is a weak bond between the two proteins. If your protein may form a homodimer, I think the probability of this happening is much smaller, so you may need to adopt other methods to determine whether your protein is a dimer or a monomer. You can analyze the results of SDS-PAGE and Native-PAGE in combination with the peak position of the gel filtration.
All the best!
Dear Sherif
i think that to confirm your hypothesis that the protein run as a dimer in SEC, if you can, is better it you to load it in a Superdex 75 that is more appropriate than a Supedex 200 to distinguish mw between 28 (monomer=?) and 56(dimer?)
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