Cell Biologists use many solutions with complex formulations (ie containing 3 or more chemical components), and sometimes as many as 10 different solutions may be used in a single experiment. Preparing each solution from scratch, by weighing and dissolving each chemical, would be quite tedious. A convenient approach which allows solutions to be prepared just in time as needed, is to start with concentrated stock solutions. Calculated quantities of stock solutions can be pipeted and diluted with water to desired final concentration. Complex solutions are made by pipeting the appropriate quantity of each stock solution into a graduated cylinder, and then adding water to the final desired volume. All quantities of stock solution are added to one beaker before topping off to the final volume. Note that you do NOT dilute each one individually and then combine ! Below are some practice problems illustrating how this is done. Be careful with, and indicate, the units! You start with the following Stock Solutions on your shelf: A. 1 M Tris-Cl, pH 8.0
B. 0.5 M EDTA
C. 5 M NaCl
D. 0.2 M Na
Phosphate Buffer pH 7.0 E. 10 mM ONPG F. 20% (W/V) Triton X-100 G. 25 mM Cytochrome C Indicate how (how much chemicals, how much water) each of the following complex solutions would be prepared:
1. 50 mM Tris-Cl pH 8.0 20 mM NaCl 1 mM EDTA Make 100 mL
2. 50 mM Na Phosphate Buffer 5 mM EDTA 50 mM NaCl 1% TX-100 Make 100 mL
3. 100 uM ONPG 0.02 M Na Phosphate Buffer 5 mM NaCl Make 100 mL
4. 25 uM Cytochrome C 100 mM Na Phosphate Buffer 5 mM NaCl Make 10 mL