I have a start volume of 530ul crosslinked protein sample. I want to precipitate it. The Methanol/Chloroform and acetone methods require quite a bit of volume for precipitation, making it so that I cannot stay under 2ml volume. Now i don't have a bigger centrifuge that can centrifuge at a speed higher than 4200g, so I cannot centrifuge samples above 2ml at 9000g (which is the recommended speed). Because the difference in speed is quite big, I am looking for a different method to precipitate proteins with such a high starting volume. I already tried TCA precipitation, but the pellet is almost impossible to completely dissolve. If anyone knows a different method for protein precipitation, please let me know.
How about dividing your sample into two tubes, adding methanol/chloroform or acetone, centrifuging and then taking up each precipitate into a small volume of buffer, followed by pooling the two samples ?
Yes that is what i tried last time after I found out the big centrifuge wouldn't work out in the middle of the experiment. I probably didn't vortex properly because the precipitate did not form well and was still stuck in the interface instead of the bottom of the tube. It was impossible to remove the methanol away without disturbing the pellet. But my supervisor was not very fond of the idea of dividing the sample in smaller tubes. She told me to look for a low volume method, would be better.
Acetone precipitation at cold temperatures is straightforward. For 250 ul of sample add 1 ml of acetone at -20 C. Put the mixture on the freezer overnight.
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