When you select Start from the menu, you will be able to select a new mixture or one that has been stored after a previous purification attempt. Alternatively, you can simply select the default mixture of twenty proteins. Before you start, you must nominate the protein which you intend to purify. You will find that your protein has an enzymic activity for which an assay has already been developed. Your technician has also screened the laboratory's extensive collection of antibodies and antisera and selected three monoclonal antibody preparations and one polyclonal antiserum which appear to be specific for your protein. However, the technician is not pleased about being directed by a newcomer to the team and is somewhat sulky. While your instructions will be carried out precisely and the results will be presented to you, the technician will not give you advice or warn you if you make mistakes. You are in charge. You must make the decisions and cope with the consequences. Bear in mind that if you lose the enzymic activity, take more than ten steps to purify the protein or allow the cost to rise too high, you will come under the scrutiny of the laboratory's financial advisers. Try to avoid this!