Difference between revisions of "20.109(S11):Purify aptamer-encoding DNA (Day2)"
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Gel electrophoresis is a technique used to separate large molecules by size using an applied electrical field and appropriate sieving matrix. DNA fragments are typically separated in gels composed of agarose, a seaweed-derived polymer (see figure, below left). To prepare these gels, molten agarose is poured into a horizontal casting tray containing a comb. Once the agarose has solidified, the comb is removed, leaving wells into which the DNA sample can be loaded. The loaded DNA samples are then pulled through the matrix when a current is applied across it. Specifically, DNA molecules are negatively charged due to their phosphate backbones, and thus travel toward the positive charge at the far end of the gel (see figure, below right). | Gel electrophoresis is a technique used to separate large molecules by size using an applied electrical field and appropriate sieving matrix. DNA fragments are typically separated in gels composed of agarose, a seaweed-derived polymer (see figure, below left). To prepare these gels, molten agarose is poured into a horizontal casting tray containing a comb. Once the agarose has solidified, the comb is removed, leaving wells into which the DNA sample can be loaded. The loaded DNA samples are then pulled through the matrix when a current is applied across it. Specifically, DNA molecules are negatively charged due to their phosphate backbones, and thus travel toward the positive charge at the far end of the gel (see figure, below right). | ||
− | [[Image:Be109agarosegelEM.jpg|thumb| | + | [[Image:Be109agarosegelEM.jpg|thumb|250px|left| Scanning EM image of agarose polymer]] |
− | [[Image:Be109agarosegelsetup.jpg|thumb|center| | + | [[Image:Be109agarosegelsetup.jpg|thumb|center|500px]] |
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− | Although all DNA molecules travel in the same direction during gel electrophoresis, they do so at different rates: larger molecules get entwined in the matrix and retarded, while smaller molecules wind through the matrix more quickly and thus travel further from the well. Ultimately, fragments of similar length accumulate into | + | Although all DNA molecules travel in the same direction during gel electrophoresis, they do so at different rates: larger molecules get entwined in the matrix and retarded, while smaller molecules wind through the matrix more quickly and thus travel further from the well. Ultimately, fragments of similar length accumulate into |