Does a drug change a protein?

A learning pathway in six steps for students of molecular neuroscience and experimental design. It follows one question, from the prediction to the limits of the answer, and uses the Western blotting guided experiment for the measurement.

Before starting

The pathway assumes a basic knowledge of cells, genes and proteins; the Cells of the brain page and the glossary cover the terms used. At the end, the answers written at each step form a worksheet: a study plan, the analysis decisions, a summary of the result, its limitations and a proposed next experiment, which can be saved as a file or printed and discussed with a supervisor or teacher.

The answers are kept in this browser only and are not sent to GloNeuro. The pathway is practice in reasoning about an experiment; it is not training or certification in laboratory work.

Teachers and supervisors will find notes, a worked example, common misconceptions and an assessment rubric on Teaching the pathway.

1. The question

Gx is a hypothetical protein of about 55 kDa in the hippocampus of the mouse. A research group asks whether a drug, given for seven days, changes the amount of Gx. Mice receive either the drug or the vehicle (the same solution without the drug), allocated at random.

State the question in one sentence, then the prediction. A useful prediction also says which result would count against it.

The question The prediction, and the result that would count against it This step is complete

2. What to measure

Three methods on GloNeuro measure different things about Gx:

RT-qPCR measures the amount of the mRNA that codes for Gx.
Western blotting measures the amount of Gx protein in a tissue extract, relative to the other samples on the same blot.
Immunofluorescence microscopy shows where a protein is in a tissue section and in which cells.

The amount of an mRNA and the amount of its protein do not always change together, because the level of a protein also depends on how fast it is made from the mRNA and how fast it is broken down. A change in Gx mRNA is therefore not evidence of a change in Gx protein, or the reverse.

The method that answers the question, and why What this method cannot show This step is complete

3. The plan

Decide the design before any data are collected. The independent unit is the unit to which the treatment is applied independently and which is counted as n in the statistics; the controls show what the result would be without the drug and whether the measurement worked; coding the samples and allocating animals at random protect the comparison from bias. The research design pages explain these ideas, and the Experiment Design Studio can be used to draft the plan in full.

The independent unit, and the number per group The controls Allocation and blinding The analysis planned in advance This step is complete

4. The experiment

Carry out the Western blotting guided experiment, choosing the drug question at the first station. Its stations follow the procedure from tissue to statistics: lysis and the protein assay, the gel and the transfer, antibodies and exposure, blind quantification and the comparison of the groups. Progress in the experiment is saved in this browser, so it can be left and resumed.

Notes from the experiment, such as the choices made and the estimate obtained This step is complete

5. The result

A result is the estimate of the difference between the groups together with its uncertainty, such as a 95% confidence interval; a p-value alone does not give the size of an effect. Before interpreting the estimate, check the measurement itself:

Loading: were equal amounts of protein loaded, and does the treatment itself change the loading control?
Specificity: does the antibody give a single band at the expected size, and is the band absent from tissue that lacks the protein?
Saturation: are the strongest bands within the range in which the signal still increases with the amount of protein?

The result in two sentences, with its uncertainty The checks on loading, specificity and saturation This step is complete

6. The limits

A difference in the amount of Gx in hippocampal tissue after seven days of treatment is one observation. On its own it does not show how the drug changes Gx, in which cells the change occurs, whether the function of the hippocampus changes, or whether the drug would alter a disease. It also applies only to the conditions studied: the dose, the duration, the animals and the tissue.

What this evidence does not establish One next experiment, and the result that would change the conclusion This step is complete

The worksheet

The answers above form the worksheet. It can be saved as a text file in Markdown format or printed. A completed worksheet is a record of the reasoning, not a grade or a certificate.

Last updated 8 November 2026