Thursday, January 22, 2015

bio125, Thu, bradford protein concentration determination

Section 1:
8am. Announcement:
office hours, wed 1-5pm. 
Books on SpelElearn common site
Student demo, recording
How to use pipette
Go over serial dilution protocol.

Studens were asked to figure out way to perform experiement on their own, only asking for help when they are 'challenged'.

by 8:30, student finished protocol presentation, demonstrated pipette usage.
I then went over R code on standard curve preparation and analysis. I explained that sample codes will always provide to students in bio125.
R and Rstudio demo for data analysis

I explained how to save pictures in Rstudio

Serial dilution
Bradford protein concentration determination

9:10am. Lab instructor started the lab. BSA stock in eppen tube. Unknown samples are labeled by numbers.

Some student continue to work at 10:45am.

Problems: Students are not clearly about 5X and 1X. This convention was not explained in the protocol. (Wang said 5X is in Math4)

Students were not sure how to label cuvettes. 
Wrong wavelength was used by one student.
Wrong orientation of cuvett in spec: A group measue OD by putting cuvett sideways. 
Some BSA stock does not have glycerol. Kioko thought protein may fall out of water and lead to low concentration. 

Many students have trouble to figure the concentration of the original solution Unknown. I used the following figure to explain them.

Kioko: Bradford staining is irreversible. In other words, stained over-concentrated proteins in the cuvette cannot be diluted. So, if the measurement shoot over the standard curve, students has to dilute from the concentrate protein stock again to make it landed in the range.
Kioko: Add Bradford stock as a the last solution to the tube, ensuring staining reaction occur to the same extent.  

Kioko also said the students did the serial dilution experiment in bio120.

skipped: Linear fitting, R2 and p-value
Review homework and assignment. No time, leave for next class.

Section 2:
1/3 students did not read protocol or finish quiz for the lab.

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