User:Keyun Wang/Notebook/Experimental Biological Chemistry I/2012/11/07

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  • Bradford assay was run to test the concentration of ADA protein purified through FPLC on 10/03/2012 and 11/06/2012
  • Au/HRP samples were made at the following mole ratios: 10, 50, 100, 150, 200, 250, 300, 350, 400, 450.

Procedure for Bradford Assay

  • BSA from Signma Aldrich® was used to make a stock solution of 1mg/mL. BSA stock solution was made the following way:
    • 10mg of BSA was weighted out
    • 10mg of BSA was poured into a 10mL volumetric flask
    • 10mL of sterile water was added to the 10ml volumetric flask
    • BSA and water were mixed until dissolved
  • 6X Bradford reagent from Bio Rad® was diluted 6 fold to make 1X Bradford reagent. 1X Bradford was diluted by mixing 4mL of 6X Bradford reagent with 20mL of sterile water. 1X Bradford reagent was used to make Bradford assay standard solutions.
  • Standard solutions were made with different amounts of 1mg/mL BSA, 1X bradford reagent, and water. All sample solutions made up a total volume of 1.7mL to place in plastic cuvette. The volume of each reagent used are listed in table below:
BSA added[mL] 1X Bradford Reagent added[mL] Sterile Water added[mL]
0 1.4 0.03
0.005 1.4 0.025
0.01 1.4 0.02
0.015 1.4 0.015
0.02 1.4 0.01
0.025 1.4 0.005
0.03 1.4 0
  • Each samples in plastic cuvette were placed in UV-vis spectrometer under spectrum method with wavelength ranging from 500nm to 800nm. The absorbance was recorded for analysis.
  • After the Bradford assay were run, 7.5μL of ADA protein fractions were mixed with 715μL 1X Bradford assay and 7.5μL water to test absorbance at 595nm.

Results and Calculations of ADA protein Concentrations

  • The calculated final BSA concentration is shown in table below:
Volume BSA Stock Added [mL] VolumeTotal [mL] [BSA] [mg/mL]
0 1.7 0
0.005 1.7 0.003566434
0.01 1.7 0.007132867
0.015 1.7 0.010699301
0.02 1.7 0.014265734
0.025 1.7 0.017832168
0.03 1.7 0.021398601
  • Absorbance at 595nm were plotted on a graph against the final concentration of BSA used before putting into UV-vis spectrometer. The graph is shown below:

Bradford assay.png

  • Best fit line was shown in graph as function to calculate ADA protein concentration once absorbance was measured. The absorbance for ADA protein was kept below 1 to make sure measurement was within the limit of Bradford assay.
  • With the calculated best fit line, the absorbance of each protein fraction was used to calculate ADA protein concentration by fitting into the equation:
  Absorbance = 27.609 * [BSA]mg/mL + 0.4363
  • Table including the absorbance obtained and final calculated ADA protein concentration in molarity is listed below:
- Absorbance [] Conc. ADA [mg/mL] Mass of ADA [mg] Moles of ADA [mol] Molar Absorptivity of ADA [mL/mg cm] Molarity [M]
Fraction Oct 0.784 0.012459254 0.017816733 4.38E-10 62.92511628 5.84E-05
Fraction 2 0.559 0.004310033 0.006163347 1.51E-10 129.697395 4.66E-05
Fraction 1&3 0.501 0.002209344 0.003159363 7.76E-11 226.7640984 1.04E-05
  • Thus, the final concentration of ADA protein fraction made on 10/03/2012 is 58.4mM. Final concentration of ADA protein fraction 2 made on 11/06/2012 is 46.6mM. And final concentration of ADA protein fraction 1&3 made on the same day is 10.4mM.

Procedure for Making Au/HRP samples

  • Au/HRP samples were made with the mole ratios listed below:
  10 - 50 - 100 - 150 - 200 - 250 - 300 - 350 - 400 - 450