电泳Electrophoresis

粒子迁移速度 v = μE，电泳迁移率 μ 取决于电荷、大小和形状以及介质的黏度。在凝胶中，凝胶网孔起分子筛作用，小分子跑得快。SDS-PAGE 中十二烷基硫酸钠使蛋白质变性并带上与长度成比例的负电荷，电荷差异被消除，蛋白质按分子量分离。DNA 带均匀负电荷（磷酸骨架），在琼脂糖凝胶中按片段长度分离，用溴化乙锭或 SYBR 染料在紫外下显色。等电聚焦在 pH 梯度中按等电点分离蛋白质。

Migration velocity v = μE, where the electrophoretic mobility μ depends on charge, size, shape and the viscosity of the medium. In gels the pores act as a molecular sieve, so small molecules run faster. In SDS-PAGE, sodium dodecyl sulfate denatures proteins and coats them with negative charge in proportion to length, cancelling charge differences so they separate by mass. DNA, uniformly charged by its phosphate backbone, separates by fragment length in agarose and is stained with ethidium bromide or SYBR dyes under UV. Isoelectric focusing separates proteins by isoelectric point in a pH gradient.

1807 年俄国物理学家罗伊斯观察到黏土颗粒在电场中移动。1937 年瑞典化学家蒂塞利乌斯发明移动界面电泳仪，把血清蛋白分为白蛋白和 α、β、γ 球蛋白，获 1948 年诺贝尔化学奖。1955 年史密斯斯发明淀粉凝胶电泳，1959 年雷蒙德等引入聚丙烯酰胺凝胶，1970 年莱姆利建立 SDS-PAGE 方法，1981 年约根森发展毛细管电泳。

In 1807 the Russian physicist Reuss saw clay particles move in an electric field. In 1937 the Swedish chemist Arne Tiselius invented moving-boundary electrophoresis and separated serum proteins into albumin and α, β and γ globulins, earning the 1948 Nobel Prize in Chemistry. Smithies introduced starch-gel electrophoresis in 1955, Raymond and others polyacrylamide gels in 1959, Laemmli the SDS-PAGE method in 1970 and Jorgenson capillary electrophoresis in 1981.

电泳用于蛋白质纯度和分子量测定、蛋白质印迹（Western blot）、DNA 片段分析和 PCR 产物检测、DNA 测序（毛细管电泳测序完成了人类基因组计划）、DNA 指纹法医鉴定、临床血清蛋白电泳诊断多发性骨髓瘤，以及双向电泳蛋白质组学。

Electrophoresis checks protein purity and molecular weight, underlies Western blotting, analyses DNA fragments and PCR products, sequenced DNA (capillary electrophoresis completed the Human Genome Project), supports DNA forensics, diagnoses multiple myeloma by serum protein electrophoresis, and in two-dimensional form drives proteomics.