teaching electrophoresis to freshmen

David L. Robinson dlrobi02 at HOMER.LOUISVILLE.EDU
Mon Jun 17 18:24:32 EST 1996

I am currently developing the laboratory component of a freshman, 
introductory biology class (for majors) that I teach in the fall. 
I want to demonstrate electrophoresis in lab, and am trying to 
figure out the most effective way to do it. Does anyone have any 
good ideas?

I know I could do a demonstration SDS-protein gel showing the protein 
profiles of different species/tissues, or I could do lambda 
restriction digests and run a DNA gel, but: 1) I only have 3 hours per
lab period for each group of students, 2) I teach multiple sections so this 
would be really a strain in terms of time and expense, 3) I'd rather not 
have a bunch of 18-year-olds playing around with things like acrylamide, 
ethidium bromide, etc. 4) I could just as easily show publication-quality 
photos of protein or DNA gels that are already in the literature 
or textbooks....what I really want them to appreciate is the *concept* 
of electrophoresis.....that you can separate molecules based on their 
size, charge and shape using an electric field. Once they understand 
that then they can start to deal with actual protein/DNA/RNA gels.

Last year, after I had them do paper chromatography exercises in 
separating chlorophyll and then amino acids I was able to just say that 
electrophoresis was "sort of like that except.....la la la". But I am 
not sure paper chromatography is conceptually a real good analogy for 
electrophoresis! Plus, I would like them to at least *see* some of the basic 
equipment that is used in cellular/molecular biology even if they don't get 
to actually use it themselves.

Now my idea is to pour an agarose gel for them, and load a well with 
a single, dark solution that would be a mixture of different dyes and then 
apply current. The dyes would move at different rates and 
separate out. In my imagination they would see lots of bands of red, blue, 
green, etc that had been separated by electric force. That would be the 
end of it...without any other steps I would have demonstrated the basic 
process of electrophoresis. Comments?????

Does anyone have any good ideas for what dyes would be good for this?
I can use bromophenol blue and xylene cyanole as they are different in 
color and mobility in an agarose system.....what other dyes of different 
color and mobility can I add to this mixture?

Thanks for any advice.

Dave Lowell Robinson      dlrobi02 at homer.louisville.edu
Biology Department
Bellarmine College
Louisville, KY 

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