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MIA
Protein Purification
Woo | Hoo |
---|---|
Gel filtration chromatography (size) | big molecules have a shorted path because they cannot fit trough, can only go around. medium is a bit longer. small is longest, can fit through so must go through all. |
Dialysis | Semi-permeable membrane (excludes material at molecular level), Permeable (allows small molecules and water to pass), Impermeable (does not allow large molecules). |
Dialysis | for rapid dialysis, maximise area of membrane/volume of solution. |
SDS-page | Similar to electrophoresis but SDSP added to sample which applies a negative charge to each protein in proportion to its mass. SDS allows proteins to be separated strictly by molecular weight. |
Silver stain | used to make invisible protein bands visible (BLACK) |
Comassie blue | makes protein bands blue, less sensitive. |
Mass spectrometry | Accurate reading of molecular weight, down to a single atom. |
Cation-exchange chromatography | Has -vely charged polymer beads. Rate of movement determined by net charge at the pH used. More -ve proteins move faster because like charges repel. |
Isoelectric focussing IEF | Charge on a protein is affected by pH. A pH gradient is set up and an electric current is passed through. When protein reached pI, it stops. |
2D-PAGE | first dimension = IEF, separation by charge. second dimension = SDS-PAGE, separation by size. decreasing Mr vertically, decreasing pI horizontally. |