¹H NMR spectra from biopolymers give chemical shifts classified according to proton type and often suffer from signal degeneracy. Data from nucleic acids are particularly prone to this failing. Recent developments in proton broadband decoupling techniques with the promise of enhanced resolution at full sensitivity have allowed us to investigate the application of homonuclear band-selective (HOBS) decoupling to the study of small synthetic DNA molecules and to compare these with results from classical and pure shift techniques. Improved signal resolution at full sensitivity in both HOBS-1D ¹H and HOBS-2D [¹H, ¹H] NOESY NMR data is reported for three example small DNA molecules. Comparisons of ¹H T₁ and integrals of signals from HOBS-1D ¹H and HOBS-2D [¹H, ¹H] NOESY NMR data with those of standard data collection methods are also reported. The results show that homonuclear HOBS-NOESY data are useful for data assignment purposes and have some merit for quantification purposes. In general, we show that resolution and sensitivity enhancement of ¹H NMR data for small DNA samples may be achieved without recourse to higher magnetic field strength at full sensitivity in a band-selected manner. Copyright © 2014 John Wiley & Sons, Ltd.

The entire family of noncomplementary hexamer oligodeoxyribonucleotides d(GCXYGC) (X and Y = A, G, C, or T) were assessed for topological indicators and equilibrium thermodynamics using a priori molecular modeling and solution phase NMR spectroscopy. Feasible modeled hairpin structures formed a basis from which solution structure and equilibria for each oligonucleotide were considered. ¹H and ³¹P variable temperature-dependent (VT) and concentration-dependent NMR data, NMR signal assignments, and diffusion parameters led to d(GCGAGC) and d(GCGGGC) being understood as exceptions within the family in terms of self-association and topological character. A mean diffusion coefficient D_{298 K} = (2.0 ± 0.07) × 10⁻¹⁰ m² s⁻¹ was evaluated across all hexamers except for d(GCGAGC) (D_{298 K} = 1.7 × 10⁻¹⁰ m² s⁻¹) and d(GCGGGC) (D_{298 K} = 1.2 × 10⁻¹⁰ m² s⁻¹). Melting under VT analysis (T_m = 323 K) combined with supporting NMR evidence confirmed d(GCGAGC) as the shortest tandem sheared GA mismatched duplex. Diffusion measurements were used to conclude that d(GCGGGC) preferentially exists as the shortest stable quadruplex structure. Thermodynamic analysis of all data led to the assertion that, with the exception of XY = GA and GG, the remaining noncomplementary oligonucleotides adopt equilibria between monomer and duplex, contributed largely by monomer random-coil forms. Contrastingly, d(GCGAGC) showed preference for tandem sheared GA mismatch duplex formation with an association constant K = 3.9 × 10⁵M⁻¹. No direct evidence was acquired for hairpin formation in any instance although its potential existence is considered possible for d(GCGAGC) on the basis of molecular modeling studies. © 2010 Wiley Periodicals, Inc. Biopolymers 93: 1023–1038, 2010.

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