Weak binding can also be measured with Biacore® instruments, though studies like those described above for kinetic analyses do not always afford accurate values for rate and affinity constants. Typically, weak binding is due to poor affinities (usually with values of KD between 1 µM and 1 mM). On and off rates are typically high, yielding curves that rise and fall rapidly, with flat or nearly flat plateaus, which reflect steady-state binding. This makes curve fitting difficult. Binding and rate constants for steady state binding can be determined from weak binding reactions when affinities are in the low to mid micromolar range, however. An example is shown below. The affinity determined from this study is 3.4 x 10-6 M.