BIOS 312 Cell Biology Laboratory
Name: ________________________________________________________________________
TA: ____________________ FALL SPRING SUMMER YEAR: ___________
Complete the following assignment related to the exercise Measuring Protein Concentration. Homework must be submitted using the link provided in your Blackboard weekly folder before 11:59 pm on Friday of the week it is due. Upload your completed assignment as a PDF, DOC, or DOCX file. Do NOT submit a JPG image of your homework! This will not be accepted, and you will not receive any credit. Your assignment will be checked with the plagiarism detection software SafeAssign to verify that you did not copy the work of another current or past student in the course. Feel free to attach extra pages if you need more space.
1. (8 points) In the lab, you used a set of BSA standards with known concentrations that were prepared by diluting a stock solution of BSA. Calculate the final concentration of BSA in each problem below using the formula:
C1xV1 = C2xV2
where C1 and V1 are the concentration and volume of the undiluted stock solution, and C2 and V2 are the concentration and volume of the final diluted solution. Your answers must be numerically correct and expressed in proper units (1 pt) and show how the value was arrived at using the formula above (1 pt) for you to receive full credit.
A. 300 μL of 2.5 mg/mL BSA are mixed with 700 μL of TBS. [2 pts]
B. 50 μL of 1.25 mg/mL BSA are mixed with 450 μL of dH2O and 500 μL of Bradford dye reagent. [2 pts]
C. 10 μL of 0.75 mg/mL BSA are mixed with 990 μL of TBS. [2 pts]
D. 10 μL of 0.125 mg/mL BSA are mixed with 990 μL of TBS. [2 pts]
2. (4 points) In your own words, describe two things you did to prevent protein degradation while working with your samples. List each precaution you took (1 pt) and then explain how it helped to prevent degradation of proteins (1 pt). Explanations must be accurate.
Precaution 1 [1 pt]
How it prevented protein degradation [1 pt]
Precaution 2 [1 pt]
How it prevented protein degradation [1 pt]
3. (8 points) Use Microsoft Excel or an equivalent program to prepare an XY scatter plot of the absorbance data your group collected from the protein standard samples during EITHER the Measuring Protein Concentration OR the Protein Quantitation in Unknowns exercise. Format your graph according to the following guidelines:
- Absorbance (the variable you measured) should be plotted on the Y axis [1 pt]. Absorbance is an absolute value and does not have units, but the Y axis should be labeled to indicate the appropriate wavelength [1 pt].
- BSA concentration (the variable you controlled) should be plotted on the X axis [1 pt]. The X axis must be labeled appropriately and include proper units [1 pt].
- A linear regression trendline should be plotted through your data points [1 pt]. Display the R2 value (correlation coefficient) and the equation for the line on your chart [1 pt].
- An appropriate figure legend should be displayed BELOW your graph, NOT on the chart itself. The legend can be added after the graph is created and should include a title [1 pt] and a description [1 pt] of what the figure is showing.
An example of a properly formatted graph is shown on the next page.
Figure 1. Bradford Assay Standard Curve. Known concentrations of BSA were mixed with Bradford reagent and the absorbance at 595 nm was determined with a spectrophotometer.
The Title is highlighted in yellow above for clarity. The Description is highlighted in blue. Both parts make up the Figure Legend. Yours should not be highlighted and you may NOT just copy the example above (i.e. you’ll need to come up with your own title and description.)
Instructions for preparing XY scatter plot graphs in Excel can be found at:
Instructions for adding a linear trendline in Excel can be found at:
These instructions were written for Excel 2010 but they will work for later versions
Once you have completed your graph, including the trendline, equation, and R2 value, copy and paste it into the final page of your assignment as a JPG picture, not an Excel object. You can then add your legend below the figure. DO NOT UPLOAD THE ORIGINAL SCATTER PLOT AS A SEPARATE FILE.
