Columbia University Summer Research Program for Science Teachers
How do we operate the spectrophotometer?
Jose Merced, John Dewey H.S., Brooklyn, NY
Mentor: Alan Stall, Department of Microbiology, College of Physicians and Surgeons
Columbia University, New York, NY
What ideas do you
have for developing an Action Plan in this area?
I would like to share with my students three things that I feel
would enrich my lessons:
a) The first is electrophoretic methods.
Electrophoresis is the movement of charged particles in an electric field. It has been applied to the movement of cells in suspension and of colloidal particles. It is useful in clinical chemistry for the identification of proteins.[Content Standard E- Understandings about technology] The rate of movement depends not only on the intensity of the electric field but also on the size, shape, and electric charge of the colloidal particle or molecule. Therefore, in making identification it may be helpful to perform electrophoresis at more than one pH.
Free and zone electrophoresis differ from each other in that
the former a solution of the charged particle is placed directly
in the electric field and analyzed. In the latter the solution
being analyzed is supported on filter paper, a layer of starch
granules, an agar gel, or some other solid or semisolid medium.
This latter technique is simpler in decreasing the interference
from diffusion and in providing stability to the separated
fractions, since they are in a solid medium rather than in a
liquid.
b) The second is the use of the hemacytometer.
The hemacytometer is a heavy glass slide manufactured to
precise specifications of the National Bureau of Standards (NBS).
It is used routinely in performing laboratory procedures such as
red blood cell counts, white blood cell counts, and platelet
counts but may also be used to count cells in other body fluids.
c) Use of the spectrophotometer to perform quantitative analysis of antibody and antigen precipitation reactions.
Students would benefit in the understanding of how standard curves are used to determine unknown concentrations of various solutions.
Do you anticipate
implementation problems, and what ideas do you have about
overcoming them?
The main problem that I anticipate is the inability to utilize
viable murine cells for analysis. The method that I plan to use
to overcome this obstacle is to order synthetic blood cells or to
use yeast cells as a substitute for leukocytes. I also spent time
during this past summer using the fluorescence microscope with
attached camera to prepare projection slides that can be used in
my classroom.
Aim: How do we
operate the spectrophotometer?
I.O.: The student should be able to:
* Explain the principle of the spectrophotometer
* List the parts of the spectrophotometer
* State Beer's law
* Use the spectrophotometer
Motivation:
Write the following on the chalkboard:
Development:
1. Working in small groups, allow the students a few minutes to
experiment with a ziplock bag containing the following items:
small flashlight, piece of black cloth, tiny mirror, and a small
piece of clear plastic.
2. Have them determine the properties of light using these items.
3. Elicit that light can be transmitted and absorbed. [Content Standard B- Energy/Matter Interactions]
4. Show the students a spectrophotometer.
5. Ask them to explain how it would work, by allowing them an
opportunity to carefully inspect it.
6. List the parts and explain the function of each part. [Content Standard Unifying Concepts- Form and function]
7. Demonstrate how to use the spectrophotometer