polyakryyliamidigeeliä

Polyacrylamide gel, often abbreviated as PAGE, is a gel electrophoresis medium composed of acrylamide and bis-acrylamide monomers cross-linked to form a polyacrylamide matrix. This matrix creates a porous network that can separate molecules based on size and, in some applications, charge. It is widely used in biochemistry and molecular biology for the separation of proteins and nucleic acids.

The preparation of polyacrylamide gels involves mixing acrylamide and bis-acrylamide monomers with a buffer solution, usually containing a pH adjuster, and a polymerization initiator. Ammonium persulfate (APS) is commonly used in conjunction with tetramethylethylenediamine (TEMED) to catalyze the free-radical polymerization process, which transforms the liquid mixture into a solid gel. The concentration of acrylamide and bis-acrylamide in the gel determines the pore size, with higher concentrations leading to smaller pores and better resolution of smaller molecules.

PAGE can be performed under native conditions, where the biological molecules retain their natural folded structures and charges, or under denaturing conditions. Denaturing PAGE, most famously sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), uses a detergent like SDS to linearize proteins and coat them with a uniform negative charge. This allows for separation primarily based on molecular weight, as the charge-to-mass ratio becomes relatively constant.

After electrophoresis, the separated molecules within the gel can be visualized using various staining techniques. For proteins, common stains include Coomassie Brilliant Blue and silver staining. For nucleic acids, ethidium bromide or SYBR Green are frequently employed. PAGE is a fundamental technique for analyzing protein purity, determining molecular weights, and studying protein interactions.