LEGEND: Structure: Changing Procedures Into Legends 1

Procedures or protocols give you a step-by-step method for carrying out your experiment. Often they are lists of instructions for making up materials (solutions etc.) and what to do with these materials. When you are writing up your report, you need to change the protocol into a legend. This means you have to focus on the conditions under which the experiment was performed and not the detailed procedures you followed to make solutions etc. In this way you will give a more general description of your materials and methods.

Example Procedure: a method for measuring the activity of the enzyme alcohol dehydrogenase in liver.

  • The assay has a total volume of 1.0 ml and contains 0.5 ml 0.8 M glycine, pH 9.5, 50 µl of 60 mM NAD, 50 µl of 1 M ethanol and distilled water to 980 µl.
  • Place this mix in a 1ml cuvette and zero the spectrophotometer at 340 nm. 20 µl of a liver extract is then added. This extract was prepared by homogenising 400 mg of liver with 4 ml of a homogenising buffer, containing 50 mM Tris pH 7.5 and 1 mM dithiothreitol (DTT) to stabilise the enzymes.
  • Then measure the absorbency at 340 nm every 15 s for 5 min.
  • Convert the linear rate, expressed as a change in absorbency per min, to the number of umoles of product (NADH) per min using the extinction coefficient for NADH at 340 nm, 6.2 mM-1 cm-1.

Glossary: protocol.