However since they cannot exist long in unbound states, they don't count in statement that no stable, individual particle carries anything other than a quantized charge.

If the protein binding is reversible, then a chemical equilibrium will exist between the bound and unbound states, such that:

At electron energies even higher than the virtual levels we find a continuum of unbound states, corresponding to an ion and a free electron.

If an atom is excited into an "unbound" state the energy is no longer "quantized" and a continuous spectrum results.

For example: A prominent term in chemistry is the 'free energy of binding', which is the difference between the bound and unbound states and thus negative).

The product is usually unstable in the active site due to steric hindrances that force it to be released and return the enzyme to its initial unbound state.

A number of chelators of divalent cations have different fluorescence spectra in the bound and unbound states.

UDG undergoes a conformational change from an "open" unbound state to a "closed" DNA-bound state.

Approximately 150 sets of unbound sheets eventually found their way into the possession of Arkham House in 1959 where they were offered for sale in an unbound state.

There is an equilibrium between the unbound state, in which host and guest are separate from each other, and the bound state, in which there is a structurally defined host-guest complex: