The simulated purification of an enzyme as a 'dry' practical within an introductory course of biochemistry.

This article describes a 'dry-laboratory' practical in which the multi-step purification of an enzyme is simulated. It has been devised to be implemented with beginner undergraduates taking an introductory course in biochemistry, with the aim of giving them a glimpse of the intensity of effort involved in complex, research-oriented experiments. The purification steps simulated are: preparation of a liver soluble extract, ammonium sulfate fractionation, gel filtration, ion-exchange and dye-ligand affinity chromatography. Before the simulation, our students are familiar with the preparative and analytical techniques involved, through short 'cookbook' laboratory experiments and, in some cases, ad hoc demonstrations. For the simulation, the students are given detailed protocols of the preparative and analytical experiments, and the raw numeric or graphical data obtained. They have to perform the calculations and graphing necessary to produce a purification table. The 27-page Student Booklet needed to implement the practical is offered by the authors to interested teachers, as a printable electronic file.