20.109(S16):Homework

Due M2D2

• Your Mod1 Abstract & Data Summary is due on Monday, March 16 at 5pm.
• Your first blog post is due within 24 hours of submitting your Abstract & Data Summary. Look for an email from Shannon inviting you to the blog.
  • Please note: you need to accept the invitation to the blog within a few days of receipt or it will expire!

We will NOT collect your final worksheet this time; it is only for your benefit.

1. Next time you will perform an assay to measure total protein concentration in your cell lysate. The reagent that we will use absorbs light at 600 nm, and the amount of protein present in the lysate will be calculated as:
   • protein concentration (μg/mL) = 100 * A₆₀₀ * 10
     • where 10 = the dilution factor used to prepare the assay
     • and 100 = the conversion factor from absorbance A to concentration
   • To save time during the next lab, you should prepare an Excel spreadsheet that will automatically calculate the volume of your lysate needed to provide between 10-20 μg of total protein.
     • The variable input to the sheet will be your measured A₆₀₀ value.
     • Your sheet will be most versatile and easy to follow if each element (such as the dilution factor) is listed and labeled separately, including units.
     • The first output of your sheet will be lysate volume. Consider that you will probably want to convert the volume to μL right away.
     • Note: you will collect two samples on M2D2. You want to load the same mass of lysate on your gel for both samples.
   • When preparing your SDS-PAGE analysis, you may only load a total volume of 24 μL on the gel and 4 μL of that volume will be sample buffer (similar to the sample buffer you used in your DNA electrophoresis). Therefore, your spreadsheet should also calculate the amount of water required to adjust the total volume to 24 μL.
   • Try doing your calculations with an A₆₀₀ of 0.71. If you'd like to check your answer in advance, just email Shannon (skalford at mit dot edu) and she'll let you know if your spreadsheet works.