Chemical modification of triplex-forming oligonucleotide to promote pyrimidine motif triplex formation at physiological pH

► 3′-amino-2′,4′-BNA modified TFO significantly stabilized triplex at physiological pH. ► 3′-amino-2′,4′-BNA modified TFO promoted triplex formation at physiological pH. ► 3′-amino-2′,4′-BNA modification increased nuclease resistance of TFO in human serum. ► Number and position of TFO modification did not affect degree of triplex promotion. ► Design of TFO with increased rigidity and hydration promoted triplex formation.