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The Inhibition Effect of Photo‐Cross‐Linking between Probes in Photo‐Induced Double Duplex Invasion DNA

Double duplex invasion (DDI) DNA is a useful antigene method that inhibits expression of genomic DNA. We succeeded in performing photoinduced‐DDI (pDDI) using ultrafast photo‐cross‐linking. 5‐Cyanouracil (CNU) has been used in pDDI to inhibit photo‐cross‐linking between probes, but its importance has not been clarified. Therefore, in this study, we evaluated the effect of spacer (S) and d‐spacer (dS) that exhibit photo‐cross‐linking ability similar to that of CNU. CNU exhibited the highest pDDI efficiency, and S, dS, and T were not very different. The photo‐cross‐linking inhibitory effect was better with S and dS than with thymidine (T). Conversely, the thermal stability was significantly lower with S and dS than with T. The results suggest that the pDDI efficiency is determined by the balance between the photo‐cross‐linking inhibitory effect and the thermal stability, which is the introduction efficiency for double‐stranded DNA. Therefore, CNU, which has a photo‐cross‐linking inhibitory effect and a high Tm value, showed the highest inhibitory efficiency.