For microarray hybridization, a fraction of each library was amplified by PCR as above but with a modified dNTP mixture including 5-(3-aminoallyl)-dUTP (Ambion) in lieu of 75% of the dTTP normally in the mixture. The resulting amino-allylcontaining DNA was purified using a DNA Clean and Concentrator-5 column (Zymo Research). The eluate was heat