We rank the reactivity of the adenyl residues (A) of model DNA and RNA molecules with electropositive subnano size [Ag] n+ sites as a function of nucleic acid primary sequences and secondary structures and in the presence of biological amounts of Cl− and Na+ or Mg2+ ions. In these conditions A is markedly more reactive than any other nucleic acid bases. A reactivity is higher in ribo (r) than in deoxyribo (d) species [pA > pdA and (pA)n ≫ (pdA)n]. Base pairing decreases A reactivity in corresponding duplexes but much less in r than in d. In linear single and paired dCAG or dGAC loci, base stacking inhibits A reactivity even if A is bulged or mispaired (A.A). dA tracts are highly reactive only when dilution prevents self‐association and duplex structures. In d hairpins the solvent‐exposed A residues are reactive in CAG and GAC triloops and even more in ATC loops. Among the eight rG1N2R3A4 loops, those bearing a single A (A4) are the least reactive. The solvent‐exposed A2 is reactive, but synergistic structural transitions make the initially stacked A residues of any rGNAA loop much more reactive. Mg2+ cross‐bridging single strands via phosphates may screen A reactivity. In contrast d duplexes cross‐bridging enables “A flipping” much more in rA.U pairs than in dA.T. Mg2+ promotes A reactivity in unpaired strands. For hairpins Mg2+ binding stabilizes the stems, but according to A position in the loops, A reactivity may be abolished, reduced, or enhanced. It is emphasized that not only accessibility but also local flexibility, concerted docking, and cation and anion binding control A reactivity. © 2006 Wiley Periodicals, Inc. Biopolymers 82: 6–28, 2006 This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com

EXPLOR_STEP=$WICRI_ROOT/Sante/explor/MersV1/Data/France/Extraction

HfdSelect -h $EXPLOR_STEP/biblio.hfd -nk 000200 | SxmlIndent | more

HfdSelect -h $EXPLOR_AREA/Data/France/Extraction/biblio.hfd -nk 000200 | SxmlIndent | more

{{Explor lien
   |wiki=    Sante
   |area=    MersV1
   |flux=    France
   |étape=   Extraction
   |type=    RBID
   |clé=     ISTEX:EF465BEF4FDDB4A099C7292CB9C1C63451BB4EAA
   |texte=   Assessment of adenyl residue reactivity within model nucleic acids by surface enhanced Raman spectroscopy
}}