The synthesis of the 800-mer GFP gene on glass wool was carried out under typical conditions of phosphoramidite chemistry with little modification. The functionalized glass wool (30 mg, 29.4 nmol) was packed into an empty 0.2 µmol synthesis column. Even though the scale of the synthesis was only 29.4 nmol, to ensure complete coverage of the glass wool in every step of each synthetic cycle in the entire synthesis, the synthesizer manufacturer recommended 1 µmol synthetic cycle was used. While the conditions may be engineered to minimize reagent use considering that less reagent is needed to fill the synthesis column for the case of glass wool, which does need reagent to fill pores within the support, than that of traditional supports such as controlled pore glass (CPG), the work was not pursued in the present study. The synthesis was tested on both ABI-394 and MerMade 6 synthesizers. Even though the former consumes more solvents, it was preferred due to its shorter synthesis time. In principle, the synthesis can be carried out consecutively, which would only need for a little more than three days, we paused the synthesis two or more times to refill reagents. With the pauses, the synthesis was completed within four days. Trityl assays consistently gave 99.6% to 99.8% average stepwise yields once the synthetic cycle ran over 100 times consecutively. To tag the full-length oligo for CBP purification, the last nucleotide at the 5'end of the 800-mer was not included in the above synthesis procedure. Instead, the 799-mer with a trityl group at its 5'-end on glass wool was transferred to a column suitable for MerMade 6 synthesizer. Upon delivery of the deblocking agent, the orange color characteristic of dilute trityl cations could still be observed indicating that the existence of full-length sequences even after 799 synthetic cycles (Figure ). The last nucleotide was introduced with PTP on the MerMade 6 synthesizer, which also tagged the full-length sequences. Details are given in the supporting information. For deprotection and cleavage, the glass wool was first treated with 10% DBU in ACN, which removed the 2-cyanoethyl groups. Treatment with concentrated NH4OH under typical oligo deprotection conditions gave a mixture of 5'-tagged full-length oligo and un-tagged failure sequences as well as other impurities (Scheme 1). CBP purification was then carried out by co-polymerizing the tagged full-length oligo into a polyacrylamide gel. The failure oligos and many other types of impurities were removed by washing. This gave only the full-length oligo on the polymer. The full-length oligo was then cleaved from the gel using 80% AcOH (Scheme 1). After removing the acid, the oligo may be precipitated with nBuOH from an ammonium hydroxide solution. This is important for avoiding damage of oligo by residue acid if the oligo needs to be stored before its use. Otherwise, precipitation may be omitted. The quantity of the oligo was determined to be 27.4 µg (111 pmol) for the synthesis involving 30 mg glass wool. The overall yield for the entire 800-mer synthesis and purification was 0.38% (Entry 8, Table ).