I've found on Wikipedia, that the critical micelle concentration of sodium dodecylsulphate is 0.0082M, what is in rough agreement with value from this article:
http://jcsp.org.pk/index.php/jcsp/article/viewFile/645/310
Taking the molar weight of 288.372 g/mol, I've got CMC of ~0.24%.
From what I know, always when working with proteins, one should keep the detergent concentration above the CMC (at least 5-10-times). However, I usually find that when other studies used size exclusion chromatography of proteins with SDS, they used 0.1%, which is half of the CMC. Am I missing something or it does't really matter that much?
I've been separating proteins (ie from plasma) by SEC without SDS in mobile phase. So, I don't think it is crucial for the separation. IMO SDS (similarly like urea) is advisable in case of solubility problems or any interaction with stationary phase leading to peak tailing. Thus, lower concentration can be explained by ion-pairing function but not micelles.
Yeah, but my protein is supposed to be transmembrane, so we're trying different detergents. I've been said that nonionic and zwitterionic detergents are not good for showing dimerization, because they can cause artificial dimerization.
I bearing a grudge read my paper on the elucidation of the quaternary structure of the bovine rhodopsin. We used dodecyl maltoside above its micelar concentracion . You must to calculate the molecular weight of the detergent micela (reported by others) and to subtract it of the molecular weight of your protein after the filtration in gel. That resulting weight is the native molecular weight of your protein. more and less detergent is irrelevant, the important thing is the protein solubilization.
I can imagine it doesn't matter above the CMC, but below? Especially in case of SDS I would be afraid I will promote the denaturation of my proteins.
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