Production of 2×, 4×, and 8× length library. Lane-M: Size marker. 10 base ladder (left) and 100 base ladder (right). Lane-S: Initial synthesized library (87 mer). Lane-1U: Initial single-unit library (94 mer) made by PCR amplification. Lane-2U: Double-unit library (138 mer) made by ligation product of digested 1U. Lane-4U: quadruple-unit library (240 mer) Lane-8U: octuple-unit library (444 mer). PAGE was done with 5 % polyacrylamide, TAE buffer (pH 8.0), 8 M urea, 65°C and stained with SybrGreen I and visualized with a fluorescence imager (Bio-Rad FX).