BCH 261 Lecture 5: Biochem Notes 5
16 Feb 2017
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All proteins have an innate electrical charge that ranges from very positive to neutral to very negative depending on the specific protein. Electrophoresis is a technique that separates proteins through a matrix (gel) according to electrical properties of proteins. The rate of migration depends on size/shape and charge. Proteins move based on their charge-to-mass ratio larger and rodded proteins move slower than smaller and globular proteins. Coats proteins with uniform negative charge (~1 sds: 2 amino acids) Migration according to charge but sds gives polypeptides uniform negative charge. Smaller proteins migrate faster than larger ones. Pi is the ph at which a protein is electrically neutral. Apply proteins to a gel with a ph gradient. As proteins migrate from high to low ph, eventually each species find the ph that matches their pi. Becomes neutral and no longer responds to electrical field. Ampholyte: a substance that can act as an acid or base.
