The development of synthetic systems displaying dynamic and adaptive characteristics is a formidable challenge with wide applications from biotechnology to therapeutics. Recently, we described a dynamic and programmable nucleic acid-based system relying on the formation of reversible boronate internucleosidic linkages. The DNA- or RNA-templated system comprises a 50 -ended boronic acid probe connecting a 30 -ended ribonucleosidic oligonucleotide partner. To explore the dominant factors that control the reversible linkage, we synthesized a series of 30 -end modified ribonucleotidic strands. Evidence suggests that geometric and steric factors are key features for controlling the equilibria.