User:Keyun Wang/Notebook/Experimental Biological Chemistry I/2013/02/20

Experimental Biological Chemistry II

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Purpose To harvest starter culture for future use. To test the concentration of silver present in a solution with silver films versus time. Procedure DH5α-T1 cells were harvested. The absorbance of cells were taken at 600nm, the results are shown as follows: Cell Starter Absorbance at 600nm 1 1.927 2 1.944 3 1.939 4 1.954 The cells were centrifuged at 4700rpm, 4°C, for 30 minutes. Supernatants were poured out, leaving the pellets. Pellets were stored in -80°C until needed. Concentration of silver in 50mL of sterile water was tested via conductivity probe. 50mL of sterile water was placed in 125mL Erlenmeyer flask to resemble conditions of antibacterial tests. Newly synthesized silver-incorporated film was originally weighted out to be 0.97grams. The film was cut with scissors until its mass became 0.50grams. 1mL of 5M of KNO3 was added into 50mL of sterile water to serve as an ionic strength adjustor. 1mL of 5M KNO3 was determined by 20uL of 5M KNO3 per milliliter of solution. Silver probe was inserted first into sterile water with KNO3 to measure conductivity in units of mV. Then, 0.5g of silver film was placed in solution under occasional steering. Throughout the following four hours, the conductivity of solution was taken for every 30 minutes. The solution was then placed in room temperature for over night, final conductivity will be taken the next day. The concentration of silver, if all silver successfully leaked out into water, was calculated and shown in Melissa's Notebook. The final concentration of silver in solution, if all silver were to leak out from the film, was calculated to be 23.8uM. The upcoming pilot study testing ideal concentration of silver in solution for best antibiotic results will have a range that include this concentration.