Deletion of the O6 carbonyl group of guanosine results in 2-aminopurine riboside (2-AP). The hydrogen bonding pattern of the 2-aminopurine nucleobase (N1 acceptor, H-N2 donor) is isomeric with that of adenosine (N1 acceptor, H-N6 donor). This nucleoside allows the study of the role of exocyclic functional groups, base stacking, and hydrogen bonding patterns in purine-containing nucleic acids. For example, replacement of guanosine residues with 2-AP in the core region of hammerhead ribozymes was useful in determining their role in stabilizing the transition state of ribozyme cleavage.⁽¹⁾ The nature of hydrogen-bonding between G-A mismatches in RNA internal loops was studied with 2-AP.⁽²⁾ The role of hydrogen-bonding and stacking interactions in the stability of GNRA loops was probed using 2-AP substitutions.⁽³⁾ The thermodynamic parameters for RNA loops of the type (A)_n were determined using time-resolved spectrofluorimetry on RNAs bearing 2-AP residues in place of A residues, since 2-AP is blue fluorescent and was found to have properties in the (A)_n region that were otherwise very similar to adenosine.⁽⁴⁾ In this sense, 2-AP can be used as a non-invasive conformational probe in RNA studies. Of the different phosphoramidites that have been used for 2-aminopurine riboside incorporation into RNA oligonucleotides,^1-(5) we have chosen to offer 2-Aminopurine Riboside-CE Phosphoramidite in the particular form shown,^1,4 which appears to offer the best results in RNA synthesis yield and purity.

Ref:

1. Tuschl, T.; Ng, M. M. P.; Pieken, W.; Benseler, F.; Eckstein, F. Biochemistry 1993, 32, 11658-11668.
2. SantaLucia, J., Jr.; Kierzek, R.; Turner, D. H. J. Am. Chem. Soc. 1991, 113, 4313-4322.
3. Wörner, K.; Strube, T.; Engels, J. W. Helv. Chim. Acta 1999, 82, 2094-2104.
4. Zagorowska, I.; Adamiak, R. W. Biochemie 1996, 78, 123-130.
5. Doudna, J. A.; Szostak, J. W.; Rich, A.; Usman, N. J. Org. Chem. 1990, 55, 5547-5549.