It is worth noting that the k'off measured in this way is not wholly representative of the true natural dissociation rate, where dissociation and association are in equilibrium and a pair of dissociated binding partners still have chances to rebind. Here, any dissociated protein binding sites will be rapidly occupied by the competitors, making them unable to re-bind as under natural conditions. As a result, the 𝑘 𝑜𝑓𝑓 ′ measured in this way should be faster than natural dissociation. This is apparent by using 𝑘 𝑜𝑓𝑓 ′ to calculate the apparent 𝐾 𝑑 ′ (𝑣𝑖𝑎 𝐾 𝑑 ′ = 𝑘 𝑜𝑓𝑓 ′ /𝑘 𝑜𝑛 ) which would yield values of ~140 and ~100 nM for DC-SIGN and DC-SIGN-C, respectively. These values are about two orders of magnitude higher than those measured from the thermodynamic FRET assays above. Therefore the dissociation rate coefficient derived from competition based kinetic studies must be treated with caution: it may not reflect the true disassociation rate under natural conditions. The discrepancies are expected, particularly for multivalent binding systems where re-association regularly occurs under natural conditions due to the close proximity of multiple binding pairs within the binding area.