We describe a physico-chemical model relating measured fluorescence intensities on oligonucleotide microarrays to the underlying specific target concentration in the hybridized solution via a hyperbolic isotherm response function. The distribution of fluorescence intensities for a complete microarray is analysed in the light of this model. Results indicate that the majority of signals in a typical microarray experiment, though not those of the most highly expressed genes, belong to the low concentration, linear part of the isotherm. Nevertheless, recognising the existence of the asymptotic saturation part of the isotherm is important for interpreting this distribution over the entire intensity range.
Conrad J. Burden