How to calculate the amount of protein in your milk samples.

It is assumed that you already know how to do a trendline in Excel and that you have read the instructions dealing with data analysis of this lab that are found in the lab manual (see page 8B-10.

To make this calculation a bit easier, it is, in my opinion, better to convert the concentration of each of the standards (the tubes with the known amount of protein) from mg/ml to micrograms of protein.  This is done for you in the following table:

When doing your graph and trendline, use the Total Protein values (column 2) instead of the concentration column 1.

For each of your unknown samples (milk, whey, pellet, fractions), use the trendline equation to determine how much protein is in each sample

Then divide the value you get for each unknown sample by the number of ul sample you measured.  For example, if you found that the first milk sample had a protein value of  36 ug, you need to divide this value by the number of ul of milk you used in that particular tube.  In this case, you should have used 2 ul in the first sample, so you would need to divide 10 ug by 2 ul – and you would then get a protein concentration of 5 ug/ul for that sample.  You should have used 3 ul for the second milk sample, so you would divide the protein value of that sample by 3.  This will then give you the amount of protein in each ul of each sample.  You should average values of the same sample (like the two milks, do not average the value of milk and whey!!!!!!)

You need to determine what volume of each sample contains 20 ug of protein.  To do this, divide 20 ug by the protein concentration you calculated (in ug/ul).  For example, if your milk sample had 5 ug/ul, then 20/5 = 4 ul needed to have 20 ug.  You will need to add 2 times this volume to the gel as each sample was diluted by half with the 2X buffer.  So you will need 4 x 2 = 8 ul of the milk sample to the gel for electrophoresis.

Do this for the milk, whey, pellet and all five column fractions.