BIOTECHNOLOGY Chapter Notes - Chapter 7: Polyethylene Glycol, Dialysis Tubing, Sucrose
Document Summary
Conventional filtration separates particulate matter from fluids by passing suspensions through porous material. However, with so-called semipermeable membranes it is possible to separate dissolved molecules by virtue of their molecular dimensions. In dialysis, an aqueous solution containing both macromolecules and very small molecules is placed in a collodion bag, which is in turn placed in a large reservoir of a given buffer. Small solute molecules (except those that are highly charged) freely pass through the membrane until equilibrium is reached. To convert the solute composition within the bag into the composition wanted, the external fluid must be repeatedly changed to maintain the required final composition. Water also passes freely through the bag, thus causing concentration or dilution, depending on whether the internal solution is less or more concentrated than the external (osmotic effect). It is used to concentrate the material in the bag. polymer.
