The NN theory was developed for hybridization of short oligonucleotides in solution (45) . Its application to surface-bound oligonucleotides has not been precisely studied. Hooybergs et al. studied hybridization of 30-mer surface-bound oligonucleotides with a 20-mer linker to 30-mer targets in solution, with no, one or two evenly spaced mismatches (46) . Although NN theory was approximately corroborated, NN factors had to be recalculated to give an approximate fit to experimental data. Moreover, the adsorptive (Langmuir) behavior deviated from expectation at high target concentrations. Thus, many unresolved questions regarding hybridization behavior remain.