What defines polyacrylamide electrophoresis (PAGE)?

Polyacrylamide electrophoresis (PAGE) is specifically defined by the use of a gel matrix that is formed through the polymerization and cross-linking of acrylamide molecules. This gel provides a suitable medium for separating proteins and nucleic acids based on their size and charge. The acrylamide concentration can be adjusted to achieve different resolutions, making PAGE a versatile technique in molecular biology and biochemistry for analyzing complex mixtures.

In contrast, the other choices do not accurately represent the characteristics of PAGE. The mention of agar in one of the options refers to agarose gel electrophoresis, which is distinct from PAGE in that agarose is generally used for separating larger nucleic acid fragments. Electrophoresis in a liquid phase is more reminiscent of methods such as free-solution electrophoresis rather than the gel-based technique that PAGE employs. Finally, while electrophoresis can indeed be conducted at varying pH levels (in the context of isoelectric focusing), this feature is not inherent to the definition of PAGE itself, making the focus on acrylamide polymerization and cross-linking the defining characteristic of this method.