Mononucleotides in aqueous solution. Proton magnetic resonance studies of amino groups

Structure and Conversion Kinetics of a Bi-stable DNA i-motif: Broken Symmetry in the [d(5mCCTCC)]4 Tetramer

“…The chemical shifts of C2 amino protons are unchanged between pH 6 and pH 3, in a pH range where titration of the N3 position would induce a 1.5 ppm lowfield shift to the amino protons of the cytidine monomer (Razka, 1974). This shows that the anomalous shift is not due to incomplete N3 protonation.…”

15N and 13C nuclear magnetic resonance of deoxydinucleotide monophosphates. II. Protonation of the homo dimers deoxycytidylyl-(3′,5′)-deoxycytidine, thymidylyl-(3′,5′)-thymidine, and deoxyadenylyl-(3′,5′)-deoxyadenosine in dimethyl sulfoxide

“…9), which, in turn, becomes a better proton acceptor in the presence of CF,COOH. Comparison with Raszka's proton data on 5'-cytidine monophosphate (21) in water suggests that this amino group may be that belonging to the 5'-dpC moiety of d(CpC), which is hydrogen bonded to the phosphate group of another molecule. In agreement with this, addition of sodium phosphate to the DMSO solution (see the experimental section) changes dramatiCan.…”

“…2b is the more protonated can be found in the proton spectrum of the amino hydrogens of d(CpC) in DMSO before acid addition. Both amino protons of d(CpC) appear as broad doublets, ind~cating restricted rotation around the C4-NH2 bond (20,21). However, for one of the two amino groups the separation between the proton resonance lines is larger than for the other (see the experimental section).…”

Structure and Dynamics of Hemimethylated GATC Sites

“…For example, an NMR study of N 6 -methylated adenine in CDCl 3 solvent showed that the N 6 -methyl chemical shifts are 3.07 (cis) and 3.51 (trans) ppm (25). Another study of an N 6 -methylated adenine monomer in H 2 O observed that the methyl resonance is a doublet and that the amino proton resonance is a spin-coupled quartet (26).…”