The 800-mer oligo was characterized with Sanger sequencing. For this purpose, a portion (30 ng) of the CBP-purified 800-mer gene was subjected to PCR amplification using high fidelity DNA polymerase. The PCR product was analyzed with agarose gel electrophoresis. As shown in Figure , a band corresponding to 800-mer can be clearly observed. A portion of the PCR product was ligated into the pCR™4Blunt-TOPO™ vector and transformed into Chemically Competent E. coli cells. The transformed cells were grown on agar plates. Colony PCR was performed on selected cell colonies. The PCR products were analyzed with agarose gel electrophoresis. As shown in Figures , all the 48 colonies contained an expected band. Plasmids of the colonies were subjected to Sanger sequencing. The alignment of the sequencing data with the reference sequence is provided in the supporting information. The results are summarized in Table . Among the 48 colonies sequenced, 41 contained the correct sequence, corresponding to a success rate of 85%. The errors in the incorrect sequences include three substitutions, four singe nucleotide deletions and one 10-nt deletion. The rates for the different errors were all lower than 0.003% except for single nucleotide deletion, which had a rate of 0.0104%. The sum of the error rates was 0.0208% (Entry 13, Table ). (a) Data were from sequencing the 20 th to 48 th nucleotide region of chemically synthesized 85-mers. Oligo synthesis conditions: activation, 1H-tetrazole in ACN; capping, Ac2O in THF, 10% 1-methylimidazole in 10% pyridine/THF; oxidation, 0.02 M I2 in THF/pyridine/H2O; deblocking, 3% TCA in DCM. For more details, see reference. (b) The error rates were calculated by dividing the number of errors by the total number of nucleotides subjected to sequencing. For example, for the 1,728-mer synthesized on glass beads, a total of three G-to-A substitutions were found in the data of sequencing 16 colonies; the error rate is 3 ÷ (1,728 × 16) = 0.0109%. (c) When DCI was used as the activator, the error rate was lower. (d) 0.1% for each nucleotide. (e) dA 0.005%, dC 0.003%, dG 0.008%, T 0.002%. (f) The total error rate is the sum of individual error rates. It does not represent the probability for a specific nucleotide position in a sequence to have substitution, deletion, addition and other errors.