Method for analyzing test substance by surface plasmon resonance analysis

1. A method for analyzing the interaction of test substances with a ligand by measuring the change in the surface plasmon resonance using a surface plasmon resonance measurement device which comprises

a) a metal film,

b) a light source for generating a light beam, an optical system for allowing such a light beam to enter the interface of the metal film so that total reflection conditions can be obtained at the interface thereof and so that various incidence angles can be included,

c) a flow channel system comprising a cell formed on the above metal film, and

d) a light-detecting means for detecting the state of surface plasmon resonance by measuring the intensity of the light beam totally reflected at the above interface;

wherein the above-described method comprises:

1. supplying a solution containing two or more types of test substances after supplying a solution containing no test substances;

2. measuring the change in the surface plasmon resonance;

3. analyzing the difference between the change in the surface plasmon resonance that is predicted from the adsorption rate constant (ka) and dissociation rate constant (kd) of each of the test substances that had previously been measured and the change in the surface plasmon resonance that has actually been measured; and

4. identifying the change in the adsorption site due to adsorption of the test substances to a ligand by the above step 3 to analyze the interaction of test substances with a ligand.

2. The method of claim 1 which comprises displaying the difference between the change in the surface plasmon resonance that is predicted from the adsorption rate constant (ka) and dissociation rate constant (kd) of each of the test substances that had previously been measured and the change in the surface plasmon resonance that has actually been measured, in the form of data.

3. The method of claim 1 wherein the change in the surface plasmon resonance is measured in a state where the flow of the liquid has then been terminated after the liquid in the above-described flow channel system has been exchanged so that a solution containing no test substances is replaced with a solution containing two or more types of test substances.

4. The method of claim 1 wherein the difference between the change in the surface plasmon resonance that is predicted from the adsorption rate constant (ka) and dissociation rate constant (kd) of each of the test substances that had previously been measured and the change in the surface plasmon resonance that has actually been measured as described above is analyzed, and a test substance causing the change in the binding site due to the binding of the test substance to a ligand is identified based on the presence of the above-mentioned difference.

5. The method of claim 1 wherein the change in the surface plasmon resonance that is predicted from the adsorption rate constant (Ka) and dissociation rate constant (kd) of each of the test substances that had previously been measured is determined from the formulas (2) and (3):

ⅆ

R

ⅆ

t

=

A

·

∑

i

=

1

n

⁢

(

Ka

i

·

Cs

i

·

(

1

-

∑

i

=

1

n

⁢

θ

i

)

-

kd

i

·

θ

i

)

·

MW

i

Formula

⁢

⁢

(

2

)

wherein, in the formula (2), A represents a constant used for conversion from the adsorbed weight to SPR signals, and MW i , Cs i , θ i , Ka i , and Kd i represent the molecular weight of compound i, the concentration thereof, the adsorption site share thereof, and adsorption rate constant, and a dissociation rate constant, respectively,

ⅆ

R

ⅆ

t

=

∑

i

=

1

n

⁢

(

Ka

i

·

Cs

i

·

(

R

⁢

⁢

max

i

⁢

-

∑

i

=

1

n

⁢

R

i

)

-

kd

i

·

R

i

)

Formula

⁢

⁢

(

3

)

wherein, in the formula (3), R i represents a change in SPR signals of compound i; and Rmax i represents the maximum adsorbed SPR signals of compound i.