Microflex lrf system

The oligonucleotides were synthesized on the ABI 394 DNA/RNA Synthesizer (Applied Biosystems, Foster City, CA, USA). Reagents for automated DNA synthesis were purchased from Glen Research Co. (Sterling, VA, USA). For the synthesis of acrydite-modified oligonucleotides, termed aptaDNA and coDNA, capping of methacrylic phosphoramidite to the 5ʹ end of oligonucleotides was also performed on the above-mentioned machine. The acrydite-modified oligonucleotides were cleaved from the support and de-protected by 28% ammonia hydroxide at 60 °C for 24 h. Sequences of aptaDNA and coDNA are shown in Table 1.
Acrydite-modified oligonucleotides were purified by dialysis against phosphate buffered saline (PBS) and water for 6 h each. All modified oligonucleotides were characterized by matrix-assisted laser desorption/ionization time-of-flight mass-spectrometry (MALDI-TOF MS, microflex LRF system, Bruker Daltonics, Bremen, Germany) in the positive ion mode. Concentration of the stock solution of each oligonucleotide was determined with UV absorption of DNA at 260 nm.