Sugar protons

NOESY in 2HzO provides the assignment of nonexchangeable base and sugar proton resonances, mostly through H6/8-H1 and H6/8-H2 /2" sequential connectivities. 

Cho and co-workers reported that the amplitude of the sugar proton peak following water suppression with a T null sequence correlated well with the... 

The assignments for the anomeric sugar protons have been reversed in comparison to ref. [1] basing on recent NMR studies. 

Figure F1.4.2 The aromatic region of the 1-D 1H NMR of cyanidin gives rise to a characteristic splitting pattern (upper spectrum). The lower spectrum shows the aromatic region of the 1-D 13C compensated attached proton test (CAPT) NMR spectrum of cyanidin. This spectrum contains all the fifteen 13C resonances of the aglycone in addition to solvent signals (labeled S) and the anomeric sugar proton labeled 1". In this spectrum, the 13C nuclei which have a proton attached are represented with resonances pointing downwards, while the quaternary 13C nuclei are pointing upwards. The 1H NMR experiment was obtained within 25 sec, while the CAPT experiment was obtained within 1 hr 46 min.

Table 2. Potential reference shifts for sugar protons...

More details of the fits are given in Table 4, which shows the number of protons of each type, the observed and computed mean structural shifts, and the linear correlation coefficient r between calculated and observed values for each type of proton. It is clear that base protons are better accounted for than are sugar protons, both in terms of the mean shifts and in terms of the correlation between calculated and observed results. Probable reasons for this behavior are discussed below. 

We have noted that results for sugar proton shifts are substantially poorer than those for the bases. There are several possible reasons for this that point the way to further research. First, ring current contributions are probably the best-understood... 

The NMR resonances of the polynucleotide duplexes at the Watson-Crick protons, the base and sugar protons and the backbone phosphates would provide sufficient markers to monitor ligand-nucleic acid interactions in solution. Such an approach has great potential in adding to our current knowledge of the interactions... 

The temperature dependence of the chemical shifts of the base and sugar resonances of poly(dA-dT) in 0.1 M phosphate buffer is plotted in Figure 3. There are upfield and downfield shifts associated with the noncooperative premelting transition between 5 and 55°C while only downfield shifts are observed for most of the base and sugar protons on raising the temperature above 65°C in the noncooperative postmelting transition temperature range. 

The cooperative melting transition (midpoint, ti = 59.0°C) exhibits downfield shifts at the base and sugar H-l protons with increasing temperature but not at all the remaining sugar protons (Figure 3). 

Figure 13. The temperature dependence of the base and sugar proton resonances of poly(dA-dT) in 1M NaCl, lOmM cacodylate solution (O), and in IM (2HtC),-NCI, lOmM phosphate solution (0). (2H C).NCI was purchased from Merck and used without further purification.

Sugar Proton Chemical Shifts in the Poly(dA-dT) Duplex in 1 M NaCl Solution3... 

The nuclear magnetic resonance (n.m.r.) spectra of aldose dithioacetals dissolved in pyridine-d5 or dimethyl sulfoxide-d6 generally exhibit extensively overlapping multiplets under which most of the sugar-proton resonances lie. Peracetylation of the dithioacetal, how-... 

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