Chemical Education Today edited by Erica K. Jacobsen JCE Secondary School Editor
Classroom Activity Connections
Board-Game Gel Filtration and Affinity Chromatography by Eric A. Hunt and Sapna K. Deo*
From the Editor
Featured Activity
Games for Learning Chromatography Using well-designed games in the classroom can provide a welcome break for students while simultaneously promoting learning. One such game was shared by Charles A. Smith as the March 2004 JCE Classroom Activity. It featured simple and inexpensive materials, dice-rolling action, and a colorful simulation of column chromatography. Below, Hunt and Deo describe an extension to Smith’s Activity. They modified the original game to simulate the techniques of gel-filtration and affinity chromatography. Those interested in chromatography simulations presented as games will want to take a look at another recent article (1), in which Samide describes a game “to assist students in understanding the concepts of partition coefficient, equilibration, retention, resolution, gradient programming, and, ultimately, separation.” All this—with only a calculator, stop watch, game board, pennies, and nickels. Let the games begin!
◭ Extension to JCE Classroom Activity: #61. Checkerboard Chromatography by Charles A. Smith, J. Chem. Educ. 2004, 81, 384A–384B.
Literature Cited 1. Samide, M. J. J. Chem. Educ. 2008, 85, 1512–1514.
Supporting JCE Online Material
http://www.jce.divched.org/Journal/Issues/2009/Jan/abs19.html Abstract and keywords Full text (PDF) with links to cited JCE articles Supplement Background and game instructions for affinity and gel-filtration chromatography simulation extension
Erica K. Jacobsen is Editor, Secondary School Chemistry, JCE;
[email protected].
Biochemical Separation Simulations Column chromatography is routinely used to separate chemical components based on the interaction of the components to be separated with the stationary and mobile phase. The JCE Classroom Activity “Checkerboard Chromatography” (1) as well as a related chromatographic simulation activity where students act as molecules (2) outline simple ways to understand the principles of column chromatography. The checkerboard chromatography activity simulates liquid chromatographic separation using a paper grid, colored paper squares, and a die. This board game style activity is interactive and can be performed in a classroom or laboratory setting. The paper grid acts as a stationary phase, colored squares represent components of different polarity to be separated, and the roll of a die dictates movement of components along the paper grid (Figure 1). Using the checkerboard chromatographic activity, students can learn about the chromatographic separation and concepts such as flow rate, column length, and molecular polarity as well as understand the effect of alterations in these parameters on separation. Perhaps the most attractive feature of the activity is that it utilizes a very minimal, inexpensive set of materials. The original Activity is most applicable in educating students on the principles of analytical instrumentation.
biochemical separation methods, gel-filtration and affinity chromatography, that are usually taught in introductory biochemistry courses. Using this extension eliminates the need to purchase large quantities of expensive biological reagents to construct and use actual columns. The extension is a simulation, as is the original board game, but still provides a visual separation with the colored paper squares (see Figure 2). It may be further adapted for use at the high school level. This modification still utilizes a paper grid, colored square papers, and a die, as does the original Activity; see the online materials for specific details on implementation.
Figure 1. JCE Class room Activity #61, Checkerboard Chroma tography, utilizes simple materials to highlight the principles of column chromatography.
Checkerboard Chromatography Modification We present here an extension that modifies the checker board chromatography game to illustrate two common © Division of Chemical Education • www.JCE.DivCHED.org • Vol. 86 No. 1 January 2009 • Journal of Chemical Education
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Chemical Education Today
Classroom Activity Connections
Figure 2. A view of how the gel-filtration and affinity chromatography simulation game boards might appear during play.
Affinity Chromatography Simulation Affinity chromatography isolates a single component from a mixture by taking advantage of specific interactions unique to that component. For example, a protein that binds metals such as nickel can be purified in the presence of other non-specific proteins using a resin containing immobilized nickel. In this manner, all other components of a mixture may be washed out of the stationary phase with the mobile phase, leaving behind the component of interest. The component of interest may then be liberated from the metal-immobilized stationary phase by using a second mobile phase that contains some displacing agent (something that can remove the protein from the stationary metal). To demonstrate the principle of separation using affinity chromatography, the paper grid is designed such that the molecule that has affinity to the stationary phase gets stuck at predetermined marked spots on the stationary phase whereas unwanted molecules come off from the paper grid. The molecule with the affinity for the stationary phase is eluted using another stronger interacting molecule represented by a selected colored paper square.
molecules of three different molecular weights. The roll of the die controls their movement so that molecules with large molecular weight travel faster through the paper grid whereas the smallest molecules travel the slowest leading to separation.
Gel-Filtration Chromatography Simulation Gel-filtration chromatography utilizes a stationary phase composed of porous gel beads, making it much less specific in its interactions with the mixture to be separated. One way to visualize this separation is to pretend that the gel beads are mazes with doors that only certain sized molecules can fit through. Small molecules (beads) will enter the maze (porous gel beads) and spend more time in the stationary phase whereas the larger molecules will just go around and elute quickly. In this way, fractions are collected by size instead of by their affinity for the stationary phase. To demonstrate separation achieved using gel-filtration chromatography, the colored square papers are categorized into
1. Smith, C. A. J. Chem. Educ. 2004, 81, 384A–384B. 2. Smith C. A.; Villaescusa, F. W. J. Chem. Educ. 2003, 80, 1023– 1025.
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Using the Extension in the Classroom This board-game extension demonstrating gel filtration and affinity chromatographic separation may be adapted into an open-ended learning activity by incorporating a series of biochemical questions that highlight the necessary background theory. Questions may be asked about the effects of binding constants on affinity chromatography, the effect of molecular weight and shape on gel separation (and the problems associated with molecules similar in these respects), the related effects associated with solvent choice and buffer pH, and so on. Further modification to the activity may be done to highlight the principles of diffusion, surface area, and affinity constants. Literature Cited
Acknowledgments Sapna K. Deo extends her thanks to the National Science Foundation (CHE-0748648) for the grant support. Eric A. Hunt and Sapna K. Deo are in the Department of Chemistry & Chemical Biology at Indiana University–Purdue University Indianapolis, 402 N. Blackford Street, Indianapolis, IN 46202;
[email protected] and *
[email protected].
Journal of Chemical Education • Vol. 86 No. 1 January 2009 • www.JCE.DivCHED.org • © Division of Chemical Education
