Analyzing Molecular Probe Design. Users may wish to carefully tailor the probe structure to a specific system of interest, thus the careful design of a molecular probe is essential. The general SMART molecular probe is a feature with two main modes of modularity: shape and substituent radius (Figure ). Probe shape can significantly influence the determination of accessible pocket space. Acyclic probes allow for exploration of smaller areas with more hindrance, such as between dirhodium ligands, resulting in a more irregular pocket than macrocyclic probes (Figure ). Though both studies using SMART utilize macrocyclic probes acyclic probes are noteworthy variants that may be preferred in certain applications where high flexibility is essential, such as shape-dependent analysis.