User:Michaela Harper/Notebook/Biological Chemistry Lab/2011/10/18

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Objective To make a labeled cysteine fluorophore and to measure the conductivity of the purple fibers previously created. Description Use 2 mg of 5-(Iodoacetamido)fluorescein and 3.3 uL of cysteine stock solution. Volume of cysteine was calculated assuming 3x excess of 5 mg fluorescein, but there was not enough. Volume of cysteine was already taken, so amount of excess was altered. Add pH 7.5 50 mM Tris buffer until label is dissolved (approximately 3.95 mL) Cover the resulting solution in foil and store in the refrigerator overnight. Calculations: cysteine stock solution = 118 mg/mL cysteine molecular weight = 121.16 g/mol 5-(Iodoacetamido)fluorescein molecular weight = 515 g/mol 5 mg fluorescein x 1 g / 1000 mg x 1 mol / 515 g = 9.709 x 10-6 mol 9.709 x 10-6 mol cysteine x 121.16 g / 1 mol= 1.18 x 10-3 g cysteine = 1.18 mg cysteine 1.18 mg cysteine / 3 = 0.39 mg cysteine (for 3x excess fluorescein) 0.39 mg x 1 mL / 118 mg stock solution = 3.3 uL stock added Data Test was not conducted because of broken probes. Notes