GE HEALTHCARE Biacore T100, Handbook

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9 Kinetics and affinity analysis
9.9 Creating and editing models
188
Biacore T100 Software Handbook BR-1006-48 Edition AE
9.8.6 Affinity – Steady State 1:1
This model calculates the equilibrium dissociation constant K
D
for a 1:1
interaction from a plot of steady state binding levels (R
eq
) against analyte
concentration (C). The equation includes a term for the bulk refractive index
contribution RI, which is assumed to be the same for all samples. This term
simply serves as an offset on the R
eq
-axis.
Model parameters and reported results are
Note: Reported K
D
values that are higher than half the highest analyte
concentration used should be treated with caution. If the response
against concentration plot does not flatten out sufficiently because the
concentrations are not high enough in relation to the K
D
value, the
reported value may be unreliable. The reported K
D
value is marked as a
vertical line on the fitting plot (see Section 9.2).
9.9 Creating and editing models
To create your own models for kinetics of affinity evaluation, choose
Tools:Models from the main menu and select the type of model you want to
work with. You can use existing models as templates. Choose an existing model
from the list and click
New : answer Yes in the following dialog to create a new
model based on the chosen template or No to create a blank model. For kinetic
models, you can define a new model either as a reaction scheme describing the
interaction or as an equation defining response as a function of time.
Interaction models are described in Section 9.9.1 and equation models in
Section 9.9.2.
Predefined models cannot be edited or removed. If you want to modify a
predefined model, create a new model using the predefined model as a
template.
Note: Custom models defined in software versions earlier than 2.0 can be
imported and viewed but cannot be edited.These models do not support
evaluation of single-cycle kinetics.
Parameters Obtained from
KD Equilibrium dissociation constant (M) Fitted
Rmax Analyte binding capacity of the surface (RU) Fitted
RI Bulk refractive index contribution in the
sample Fitted
R
eq
CR
max
K
D
C
+
----------------
RI
+ =