Dear All,
Yet again a very nice post by Nick which deals with the one of those common scientific myths that needs some confusion-whacking.
Most of the people, usually grad students, believe that Agarose polymerizes to form gel! It is nothing but just a scientific myth.
So, what is polymerization? Addition polymerization is a chain reaction in which the chain carrier may be an ion or a reactive substance with a free radical that forms a covalent bond with an electron on another molecule. For instance, in polyacrylamide gel formation, TEMED induces free radical formation from ammonium persulphate (APS) and these free radicals transfer electrons to the acrylamide/bisacrylamide monomers, radicalizing them and causing them to react with each other to form the polyacrylamide chain.
And what happens in case of Agarose? Chemically, agarose is a polysaccharide, whose monomeric unit is a disaccharide of D-galactose and 3,6-anhydro-L-galactopyranose. In aqueous solutions below 35°C these polymer strands are held together in a porous gel structure by non-covalent interactions like hydrogen bonds and electrostatic interactions. Heating the solution breaks these non-covalent interactions and separates the strands. Then as the solution cools, these non-covalent interactions are re-established and the gel forms but there is no polymerization involved!
So agarose (and agar) gels form by gellation through hydrogen bonding and electrostatic interactions, not through polymerisation!
(Credits: Nick @ Bitesize)
0 comments:
Post a Comment