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SDS-PAGE sample buffer; SDS solubility - (Jul/25/2007 )

My protocol for SDS-PAGE sample buffer (which includes 12.5ml of glycerol, 15.6ml of a Tris buffer, 3.75g of SDS, a dash of bromophenol blue and water up to 50ml) called for mixing at ROOM TEMP. Instead, I mixed it in a 4 degree cooler.

The SDS appears to come out of solution when it is allowed to settle in the 50ml tube, even at room temp.

Does anyone know anything about the solubility of SDS? Is there any way to get it back into solution at this point?


you may dissolve your SDS by heating in standard 37° incubator with inversion regulary


Yep.. Fred is right. SDS precipitates in cold. That's why I always throw samples that have been stored at -20 in the heat block for a minute before loading. I also allow sample buffer to come to room temp and vortex well before using. Your recipe is also higher in SDS than mine. For 2X sample buffer I use 12.5ml stacking gel buffer, 10ml glycerol, 2.0ml of a 0.15% bromophenol blue (or 6mg/100ml), 2.7gm SDS and 5ml B-mercaptoethanol for 50ml total. I know people say you need to add the B-mercaptoethanol fresh but I've never had an issue if I freeze aliquots.