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Message | User | Date(yyyy-mm-dd) |
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Osmosis pressure in dialysing | thanh | 2001-07-10 | Click here to register. |
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I try to dialyse 50 % glycerol (MW= 92) out of my protein (MW= 42000) in PBS (phosphate buffered saline) solution. My dialysate has the same components as the PBS with 25, 12.5, 5 and 0% of glycerol, I always observe the flush of liquid in to the dialysis tube and then it is overflow. I have tried with Spectra/Por Float-A-Lyser (MWCO=5000, Cat # 235006), also with Spectra/Por Dispodialyser (MWCO=5000, Cat #: 135484) but it did not work. As the liquid went in side the tube and dilute my sample unquantitatively. Would you please recommend the better condition for dialysing glycerol out of protein. Thank you very much. I look forward to hearing your answer.
Best regards
Thanh | | |
| dave | 2001-07-10 | Click here to register. |
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 | Both glycerol and water can move through the membrane, so when you try your experiment the water does move rapidly from its higher concentration side to its lower concentration side. (More solutes means a lower concentration of water).
There are two ways to prevent this. The easiest is to use dialysis tubing and leave a lot of extra room. When you start dialyzing water will run into the tubing bag. As the glyerol dialyzes out, much of the extra water will go with it.
The other way is to use a high molecular weight absorbent like that described at http://www.spectrapor.com/dialysis/absorbent.html. Add this to the buffer outside the dialysis membrane to equalize the osmotic pressure and minimize water transfer. You'll need to do some experimenting, but if you're dialyzing 50% glycerol against 25% glycerol you'd want about 25% absorbent to equalize the pressure. |
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