Kd (dissociation constant)

The dissociation constant (Kd) describes how tightly a molecule, like a drug or a protein, binds to its target, such as a receptor. A lower Kd indicates a stronger binding, meaning the molecule prefers to stay attached, even at low concentrations. Conversely, a higher Kd suggests weaker binding, with the molecule more likely to detach. It essentially measures the balance point between binding and unbinding; a smaller Kd reflects high affinity, making the interaction more stable, while a larger Kd indicates lower affinity and less stable binding.