teaching electrophoresis to freshmen (fwd)
David L. Robinson
dlrobi02 at HOMER.LOUISVILLE.EDU
Sun Jul 7 17:07:09 EST 1996
Keeping in line with the purpose of this group I thought I would quickly
summarize the answers I got to a question I posed a couple of weeks ago
about what might be the best way to demonstrate gel electrophoresis to
freshmen. I received more than 20 replies so I will try to keep it
short. Email me if you want more of the details.
Here are some of the suggestions:
1) In addition to xylene cyanol and BPB use Orange G, Ponceau Red,
methylene green, Pyronine Y.
2) Methylene blue travels in the opposite direction of BPB, so place your
wells halfway and they will move opposite to one another.
3) Use cake coloring
4) Use common food coloring...they separate fine in agarose gels.
5) Add india ink to whatever dyes you use to "cover up" the color while
6) Use the Molecular Weight Kits that are out now that feature
different colored markers....lots of companies sell these.
7) Do column chromatography of something like hemoglobin.
8) If don't have traditional gel boxes pour the gels on glass slides
9) Other interesting comments about laboratory pedagogy...1) .are freshmen
sophisticated enough to understand pKa and deprotonation?? ....2) use a
"conceptual change" teaching model in the lab where you start off with
what the students already know and then let them experiment and see if
they can explain what they see based on these preconceptions. Then give
them the real theory behind electrophoresis after they do the initial study.
Thanks again for all who answered this query!
) If place the gel on an overhead projector the entire class can see the
gel (even as it runs).
---------- Forwarded message ----------
Date: 17 Jun 1996 16:22:38 -0700
From: David L. Robinson <dlrobi02 at homer.louisville.edu>
To: plant-ed at net.bio.net
Subject: teaching electrophoresis to freshmen
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
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
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