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Next Subject		 what membrane to use?mercyneu2001-09-06Click here to register.
I want to purify amyloglucosidase, which is MW 97,000 in a Sodium Acetate buffer to get out the glucose (~180 M.W.). What dialysis membrane do I use? I need at least 12mm in width.
 
Re: what membrane to use?
dave2001-09-06Click here to register.
Your best choice would be Spectra/Por 4 (12-14,000 MWCO). It's available in 10 (almost 12) and 25 mm flat width.

Be sure to dialyze against the same buffer. If there's very much glucose you probably want to leave a little room in the dialysis bag for expansion.
 
Re: what membrane to use?
mercyneu2001-09-07Click here to register.
How much will the bag expand? I left a little space, last time. I used 5 ml of amyloglucosidase, and ended up with 15 ml total. I'm not even sure if the glucose moved out into the buffer. I don't want to dilute the amyloglucosidase, just purify it.
 
Re: what membrane to use?
dave2001-09-10Click here to register.
I don't know what your glocose concentration is, but both the glucose and the water will move through the membrane until there is no concentration gradient across the membrane.

If you have a significant glucose concentration (more than say 0.05 molar) you should probably put a little of a high molecular weight dextran (or maybe some Spectra/Gel) in the buffer outside your dialysis bag. This will reduce the concentration of water in the outside buffer by a little bit and reduce any tendency of the water to run into the bag.

Also, be sure that the buffer outside the bag is the same as the buffer your amyloglucosidase is dissolved in. (If you dialyze against pure water, water will always run into the bag.)

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