Sometimes the path to higher standards requires an alternate route.

The use of detergents still remains the most common method for the preparation of membrane proteins for structural and biophysical studies. This is evidenced by the use of conventional detergents, such as DDM, LMNG, C8E4, and Digitonin/GDN in nearly 80% of the unique membrane protein structures determined in 2017. Despite their wide use, removal of a membrane protein from the native lipid bilayer and into a detergent micelle can possibly interfere with the structure, function, and stability of the protein(1,2). To avoid some of these issues with detergents, many systems have been developed which attempt to mimic the native lipid membrane.  These include bicelles(3), MSP-nanodiscs(4), and styrene-maleic acid copolymers (SMAs)(5).


MSP-nanodiscs have proven useful for the Cryo-EM studies of membrane proteins in a lipid environment, with over 10 unique membrane protein structures deposited since 2016. This year, two Cryo-EM structures of SMA purified membrane proteins have been published: the drug efflux pump AcrB by the labs of Stephen Muench and Vincent L.G. Postis(6), and Alternative complex III (ACIII) by the labs of John Rubinstein and Robert Gennis(7).
 
In 2017, Keller et.al. characterized the use of a new copolymer, diisobutylene/maleic acid (DIBMA) for the direct solubilization and purification of membrane proteins from a native lipid bilayer(8, 9). This crude co-polymer is obtained from BASF (Sokolan CP9) and offers a  1:1 ratio of diisobutylene and maleic acid and avoids some of the issues typically found with the SMA copolymers. DIBMA circumvents both precipitation in the presence of low concentrations of divalent cations and high absorbance issues at 280nm. In their studies, the Keller Lab concluded that DIBMA can extract a wide range of membrane proteins from native membranes to similar extents when compared to DDM and SMA.
 
Anatrace is excited to launch our version of DIBMA as a sodium salt which allows direct solubilization and purification of membrane proteins in their native lipid environment. Purified using a proprietary method, and subjected to a number of quality control tests, this copolymer is ready to be used directly and requires no additional hydrolysis, dialysis, or purification steps. DIBMA is available in three pack sizes (250 MG, 500 MG, and 1 GM).

 

 

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