POSaM oligoarray re-use. Arrays of our 20 mer gridding sequences were synthesized as described in Materials and methods. The arrays were then hybridized to Cy3- or Cy5-labeled complementary target molecules and the fluorescence intensity determined as described above. Intensities were recorded and the slides were stripped of target DNA by incubation in 20 mM NaOH for 2 min at room temperature. The fluorescence intensity of the stripped slides was measured and the slides were rehybridized using the same targets as before. These hybridizations, intensity measurements, stripping, intensity measurements, and rehybridizations were repeated at least 10 times. Stripping reduced fluorescence by an average of 99%. Signal intensity and specificity appears unchanged during the first four cycles of use. The sequences used are identical to those in Figure 8: Cy3-labeled targets are perfectly complementary; Cy5 differ by two adjacent mismatches.