Wish you all good luck in 2016!

Here I would like to get some suggestions from you guys. We are working on a membrane protein, which forms dimer. We can purify it in DDM and the SEC profile looks quite nice. We plan to use it for high resolution cryo-EM study. So we tried to exchange the detergent from DDM to MNG (LMNG, Lauryl Maltose Neopentyl Glycol from Anantrace). We did it in a way that the exchange was slow and efficient. However after the exchange all protein formed aggregates. We tried many times and all failed. We are sure it is not the way we did it because we do it regularly for other proteins and never had a problem.

The reason for using MNG is to reduce the detergent background under EM, since MNG binding is quite tight and the protein sample can be diluted below CMC. It is quite frustrating that LMNG didn't work for this protein. I would appreciate any suggestion. Like other kinds of MNG that may work or other detergents that are preferred for high resolution EM studies? Or anything else we can try.

Thanks!

Best,

Cheng 

University of Pittsburgh

PA, United States