User:Tamra L. Fisher/Notebook/Experimental Biological Chem/2011/09/07

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Objective

The main objective last week was to determine how pH effects the biomineralization of gold nanoparticles using the biomineralization procedure by Bakshi, et al (doi:10.1021/jp110296y). This week the objective is to continue to compare the biomineralization at different pHs and to also improve the biomineralization of gold nanoparticles by using higher concentrations of BSA and chloroauric acid.

Description

  1. To start a 2.5mM stock solution of chloroauric acid and a 15μM stock solution of BSA were already made.
  2. 1mL of the 2.5mM chloroauric acid and 1mL of 15μM BSA were mixed with 8mL of water at room temperature in a glass test tube. The final concentrations in this mixture were 0.25mM chloroauric acid and 1.5μM BSA.
  3. Also, 1mL of the 2.5mM chloroauric acid and 1mL of 15μM BSA were mixed with 8mL of 50mM Acetate Buffer, pH 3.6, at room temperature in a glass test tube. The final concentrations in this mixture were 0.25mM chloroauric acid and 1.5μM BSA.
  4. Spectrums from 200nm to 800nm were taken of each of these mixtures.
  5. These mixtures were placed into an 80°C oven for about 4 hours. Spectrums of each of the mixtures were taken every half hour.
  6. Spectrums of just the water and the buffer were taken for a baseline reading as well.

Data

The spectra for the mixtures this week are very different than the ones from last week. The absorbance around 220nm drops for both of these, whereas last week the absorbance stayed high over time.

This is the spectrum for the water mixture:

The absorbance at 550nm over time did not seem to have any trend or pattern in how it was increasing or decreasing:

This is the spectrum for the mixture made with the acetate buffer:

Again, the absorbance at 550nm did not have any trends:

Since there were dark purple strands in each of the mixtures that are believed to be the BSA wrapping around the gold, the absorbance at 550nm would not have increased in the solution. The gold nanoparticles seemed to precipitate out this time instead of being distributed in either the water or buffer.

Notes

  • The samples were both put in at 11:40am, and the temperature of the oven was 79°C.
  • The samples were removed at 12:10pm and the oven was 74°C.
  • The samples were put back in at 12:20pm, and the temperature of the oven was 72°C.
  • The samples were removed at 12:50pm and the oven was 74°C.
  • The samples were put back in at 1:05pm, and the temperature of the oven was 72°C.
  • The samples were removed at 1:35pm and the oven was 61°C.
  • It was observed when these were taken out was dark purple strands which are believed to be proteins wrapping around the gold. The solution remains clear, but these strands float in the solution. The water mixture had more of these strands than the buffer mixture.
  • The samples were put back in at 2:08pm, and the temperature of the oven was 68°C.
  • The samples were removed at 2:38pm and the oven was 62°C.
  • There appeared to be more of the dark purple strands in each of the mixtures. The water mixture still had more of these strands.
  • The samples were put back in at 2:56pm, and the temperature of the oven was 66°C.
  • The samples were removed at 3:36pm and the oven was 62°C.
  • The samples were wrapped in aluminum foil and stored at room temperature.



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