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DÍEZ MONTORO, R. & COL. AN. R. ACAD. NAC. FARM.

In our previous research (17-27) different features relative to the
kinetics of antigen-antibody reactions used by immunoanalytical tech-
niques were analysed. Theoretical models were prepared for an appli-
cation to the immunocomplex formation processes produced in RIA
(radioimmunoassay) and IRMA (immunoradiometric assay). We also
studied the fitting of equilibrium results to several pre-set equations,
and a mathematical deduction that justifies them theoretically was
obtained.

We seek to develop a general model applicable to competitive im-
munoassays including the influence of several variables. Its validation
comes from the fitting of the results to the equations obtained. The
models of Stenberg (9-13), Rabany (7), and those of Zuber (6) refer
to the formation of the radioactive immunocomplex but not to the
competition between labelled and unlabelled antigen, which is the ba-
sis of competitive immunoassays. Such models do not determine the
influence of the variables studied here.

In line with the above research, this paper aims to:

— Produce a kinetic model applicable to the substitution of the
labelled antigen bound to the antibody by the unlabelled one,
this process being at the foundations of RIA.

— Distinguish between single-site and two-site binding models by
analysing kinetic data.

— Determine potential diffusion control.

This must be done in different stages:

— Obtaining integrated rate equations for the overall processes.

— Studying the medium’s viscosity influence on reaction kinetics.

— Complementary analysis of ionic strength influence in order to
include or rule out the effect of electrical charges.

— To predict the calibration curves showing the influence of the
mentioned variables.

— The results must be potentially applicable to the design of im-
munoanalytical techniques.

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