User:Puja Mody/Notebook/Chem 571: Gold Nanoparticles/2012/09/19

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Protein Expression.


  • Induce Protein expression.
  • make the binding buffer and the elution buffer
  • Harvest the cells that were grown.


  • Protein Expression
  1. This morning at 8 am, the starter cultures were centrifuged at 4500 rpm for 15 minutes and then resuspended the cell pellets in 4mL of fresh LB.
  2. Inoculate the expression culture media by dividing the resuspended cells among the Fernbach flasks.
  3. Incubate the expression cultures at 37°C and 160 rpm until the absorbance of the media at 600nm = 0.6.
  4. Add 1mL of 0.4M IPTG to each flask in order to induce protein expression
  5. Continue shaking for 3-4 hours
  6. Add 30 mL of the binding buffer into each flask
  7. Harvest the cells by centrifuging at 4500rpm for 15 minutes
  8. collect the cells and place in -80°C freezer


  • Binding Buffer: 1 liter total solution at pH 7.4.

a. Theoretical calculations

  1. 20mM Tris= .020M/L Tris x1 L= .020 mols x 121.14 g/mol = 2.4228 g Tris.
    • similar calculations were done for all compounds added into the buffer solution.
  1. .5M NaCl= 29.2195 g NaCl
  2. 30mM Imidazole= 2.0424 g Imidazole
  • Elution Buffer: 500 mL total solution at pH 7.4

a. Theoretical calculations

  1. 20mM Tris= .020 × .500= .01 mols × 121.14/ 1mol= 1.2114 g Tris
    • similar calculations/stoichiometry was done for all compounded added into the buffer solution.
  1. .5M NaCl= 14.609 g NaCl
  2. .5 M imidazole= 17.019 g imidazole.


  • sample 1 looked a little different when the samples were looked at this morning prior to centrifuging. It was a different shade of yellow in the erlenmeyer flask.