IGEM:American University/2009/Notebook/Chem 672/2017/03/08

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Myoglobin templated CdS quantum dots Purpose Today we will be synthesizing CdS quantum dots in myoglobin. This was previously attempted on 2/8/2017 however the data showed broad peaks with a lot of noise. Myoglobin thus far has been the most successful protein template for CdS quantum dot synthesis so we will change the procedure in order to optimize our quantum dot yield and size at pH 4-10. Procedure Part 1: We will be attempting to synthesize CdS QD using two different methods. First we will replace the potassium thioacetate with Na2S as the sulfur containing molecule. At acidic and neutral pH's the sulfur containing molecules had no charge and -1 charge respectively. The proteins being used have negatively charged amino acid residues which cause the sulfur containing molecules at basic pH's to be repelled from the protein because it has a -2 charge. The repulsion causes a slow influx of sulfur into the protein which yields an even ratio of Cd and S in the protein cavity. We believe the acidic and neutral pH's were not repelled by the negatively charge amino acid residues which caused too large of a concentration of sulfur to insert into the protein cages at too high of a rate which causes some of the sulfur to precipitate. By using Na2S instead, we will eliminate this. Final concentrations: 12.5uM Myoglobin 1mM Cadmium acetate 10mM Na2S 40mM ammonium aacetate Ammonia water for pH adjustment HNO3 for pH adjustment DI water Part 2: The other solutions we will be making will be exactly the same as done previously, however we will also be adding ammonia water because it is expected to stabilize the cadmium and we believe this will cause more uniform quantum dots at the different pH's. Final concentrations: 12.5uM Myoglobin 1mM cadmium acetate 10mM potassium thioacetate 40mM ammonium acetate Ammonia water for pH adjustment HNO3 for pH adjustment DI water