Measurement and use of molecular interactions

An apparatus for determining the affinity between first and second binding partners, which comprises:

• (i) a surface to which one of the binding partners can be immobilised thereon;
• (ii) a means for oscillating the surface at increasing amplitude;
• and
• (iii) a means for detecting acoustic emission of the dissociation of bound binding partners that results from oscillating the surface at increasing amplitude, wherein affinity of the first and second binding partners is determined from the amplitude of oscillation at which the acoustic emission is detected.

A method for detecting dissociation of first and second binding partners, which comprises the steps of:

• (i) contacting the first and second binding partners, wherein the first binding partner is immobilised on a surface, and wherein the first and second binding partners bind to each other;
• (ii) oscillating the surface such that the amplitude of oscillation increases to a value at which the first and second binding partners dissociate;
• and
• (iii) detecting the dissociation of the first and second binding partners.

An apparatus for detecting dissociation of first and second binding partners, which comprises:

• (i) a surface to which one of the binding partners can be immobilised;
• (ii) a means for oscillating the surface at increasing amplitude in the plane of the surface;
• and
• (iii) a means for detecting the dissociation of bound binding partners that results from oscillating the surface at increasing amplitude.