Figure 1. This figure shows different scenarios that may occur when an odorant molecule (ligand) binds to an odorant receptor according to the coarse-grained model.

The red disks represent the odorant molecule, and the blue shapes represent the odorant receptor (OR) and binding pocket. The top schematic shows a mismatch because of the small molecular volume on the left, a perfect match in the center and a mismatch because of a large molecular volume on the right. The bottom schematic shows how the flexibility of an OR may compensate for molecular volume mismatches.