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Gel electrophoresis

Discussion in 'DAT Discussions' started by WayneSU, May 11, 2008.

  1. WayneSU

    WayneSU 2+ Year Member

    Nov 30, 2007
    I know that gel electrophoresis is used to separate molecules based on charge and mass. But since DNA is negatively charged, does that mean that DNA is separated solely because of mass when carrying out electrophoresis? But for proteins, it will be based on both charge and mass. Am I right?
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  3. Proteins are coated in charged molecules making all of the protein's mass/charge ratio the same, so they too are only separated my mass. I'm just speaking from memory so if you want detail look it up online or in a textbook.
  4. firenoodle

    firenoodle Member 10+ Year Member

    Aug 6, 2005
    DNA are separated base on length. depending on the concentration of the gel you have, higher percentage of gel the smaller the pore size and the more dense the gel is. smaller pore size allow for shorter DNA to penetrate faster than longer fragment size.

    From wiki:

    Proteins have varying charges and complex shapes, therefore they may not migrate into the gel at similar rates when placing a negative to positive chamber. Proteins are usually denatured in the presence of a detergent such as sodium dodecyl sulfate/sodium dodecyl phosphate (SDS/SDP) that coats the proteins with a negative charge. the resulting denatured proteins have an overall negative charge, and all the proteins have a similar charge to mass ratio. Since denatured proteins act like long rods instead of having a complex tertiary shape, the rate at which the resulting SDS coated proteins migrate in the gel is relative only to its size and not its charge or shape.

    Proteins are usually analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), by native gel electrophoresis, by quantitative preparative native continuous polyacrylamide gel electrophoresis (QPNC-PAGE), or by 2-D electrophoresis.
  5. TheWiredNerv

    TheWiredNerv 2+ Year Member

    To put it simply:
    DNA is separated by size.
    Protein is separated by size as well assuming you use SDS.

    These are the standard techniques and there are many alterations you could do.
  6. jay47

    jay47 Think Positively! 5+ Year Member

    Aug 4, 2007
    What's really cool is when you use 2-D gel electrophoresis (2DE), it separates molecules based on size vertically, and separates them based on charge horizontally (I think, u might want to check up on that). This gives you a really cool way to analyze molecules and you can compare them on many levels

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