Patent ID: 7439078

Claim:
A method for measuring the dissociation rate constant (Kd) of the reaction between an analyte molecule immobilized on a metal surface and a molecule that interacts with the analyte molecule by assaying changes in surface plasmon resonance signals using a surface plasmon resonance measurement device, comprising the steps of: i. assaying changes in the surface plasmon resonance signals using a surface plasmon resonance measurement device; and, ii. calculating the dissociation rate coefficient (Kd) using the signal and the slope of the dissociation curve of the surface plasmon resonance signal curves, or the signal ratio, wherein the dissociation rate coefficient (Kd) is calculated based on the dissociation curve of the surface plasmon resonance signal curves using any of the following equations: kd = - R ′ ⁡ ( t ) R ⁢ ⁢ ( t ) ≈ - { R ⁢ ⁢ ( t + Δ ⁢ ⁢ t ) - R ⁢ ⁢ ( t ) } Δ ⁢ ⁢ t × 1 R ⁢ ⁢ ( t ) ( 3 ) kd = 1 Δ ⁢ ⁢ t ⁢ Log ⁢ R ⁢ ⁢ ( t ) R ⁢ ⁢ ( t + Δ ⁢ ⁢ t ) ⁢ ⁢ ( the ⁢ ⁢ log ⁢ ⁢ base ⁢ ⁢ is ⁢ ⁢ '' ⁢ e ⁢ '' ) ⁢ ( 3 ′ ) wherein t represents a time; and R(t+Δt) and R(t) represent an amount of binding at the time points t+Δt and t, respectively; and, wherein changes in the surface plasmon resonance signal are measured using a surface plasmon resonance measurement device comprising a flow channel system having a cell formed on a metal film and a light-detecting means for detecting the state of surface plasmon resonance by measuring the intensity of a light beam totally reflected on the metal film, in a state where the flow of the liquid has been stopped, after the liquid contained in the above flow channel system has been exchanged from a reference liquid containing no test substance to be measured to a sample liquid containing a test substance to be measured.