Probe determination with Metabolic Design. A: The inner window of Metabolic Design showing results for designing probes with Metabolic Design and parameters (such as probe size, degeneracy or inosine composition) defined by the user. The user's chosen parameters are visible on the left, and potential probes are listed on the right. The program also displays all potential peptide combinations for each degenerate probe (named as oligopeptides) with probe listing. B: Example of probe design approach, degeneracy calculation and inosine percentage determination for the third probe in the inner window. Note that inosine residues are not taken into account for the degeneracy calculation step.