A Java Web applet is described that helps biochemistry
students learn how varying ionic strength and pH can affect separation
of proteins in an ion-exchange chromatography experiment. The applet
simulates a common scenario: a foreign protein is overexpressed in
bacteria and needs to be isolated from the other water-soluble proteins
of the cell lysate. It allows visualization of proteins on the column,
a protein output graph (absorbance at 280 nm), and polyacrylamide
gel electrophoresis analysis of selected output fractions.
The CHROM Web applet has been used
to create a new active-learning
exercise in which students design a purification scheme for a recombinant
protein using ion-exchange chromatography (IEC). To successfully complete
the exercise, students are challenged to apply elementary concepts
from acid–base chemistry as well as protein and amino acid
structure to devise a scheme purifying the target recombinant protein
from other Escherichia coli proteins. By actively
applying fundamental principles to solve an unfamiliar problem, students
develop higher-level cognitive skills and gain a deeper understanding
of key concepts that are difficult to teach effectively through traditional
methods. The effectiveness of the exercise in promoting deep learning
was assessed by comparing the performance of students in answering
questions on acid–base chemistry, amino acid structure, and
IEC before and after the completion of the active-learning exercise.
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