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QPNC-PAGE, or quantitative preparative native continuous polyacrylamide gel electrophoresis, is a high-resolution technique applied in biochemistry and bioinorganic chemistry to separate proteins by isoelectric point. This standardized variant of native gel electrophoresis is used by biologists to isolate active or native metalloproteins in biological samples and to resolve properly and improperly folded metal cofactor-containing proteins or protein isoforms in complex protein mixtures.〔 〕 ==Separation and buffering mechanisms== The aim of isoelectric focusing (IEF) is to separate proteins according to their isoelectric point (pI), thus, according to their charge at different pH values. Here, the same mechanism is accomplished in a commercially available electrophoresis chamber for separating charged biomolecules, for example, superoxide dismutase (SOD)〔 〕 or allergens,〔 〕 at continuous pH conditions and different velocities of migration depending on different isoelectric points. Due to the specific properties of the prepared gel and electrophoresis buffer solution (which is basic and contains Tris-HCl and NaN3), most proteins of a biological system are charged negatively in the solution, and will migrate from the cathode to the anode due to the electric field. At the anode, electrochemically-generated hydrogen ions react with Tris molecules to form monovalent Tris ions. The positively charged Tris ions migrate through the gel to the cathode where they neutralise hydroxide ions to form Tris molecules and water. Thus, the Tris-based buffering mechanism causes a constant pH in the buffer system.〔 〕 Although the pH value (10.00) of the electrophoresis buffer does not correspond to a physiological pH value within a cell or tissue type, the separated ring-shaped protein bands are eluted continuously into a physiological buffer solution (pH 8.00) and isolated in different fractions (see Figure ''Electropherogram''). Most protein molecules are stable in aqueous solution, at pH values from 3 to 10 if the temperature is below 50 °C. As the Joule heat generated during electrophoresis may have a negative impact on the stability and migration behavior of proteins, the separation system, including the electrophoresis chamber and a fraction collector, is cooled in a refrigerator at 4 °C (see Figure ''Equipment''). 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「QPNC-PAGE」の詳細全文を読む スポンサード リンク
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