3HR3:
reference: Interplay of structure, hydration and thermal stability in formacetal modified oligonucleotides: RNA may tolerate nonionic modifications better than DNA., Kolarovic A, Schweizer E, Greene E, Gironda M, Pallan PS, Egli M, Rozners E, J Am Chem Soc. 2009 Oct 21;131(41):14932-7. PMID: 19824732

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