Heteronuclear Multiple-quantum Coherence Experiments Research Articles

Determination of the secondary structure of the DNA binding protein Ner from phage .mu. using proton homonuclear and nitrogen-15-proton heteronuclear NMR spectroscopy

The sequential resonance assignment of the 1H and 15N NMR spectra of the DNA binding protein Ner from phage Mu is presented. This is carried out by using a combination of 1H-1H and 1H-15N two-dimensional experiments. The availability of completely labeled 15N protein enabled us to record a variety of relayed heteronuclear multiple quantum coherence experiments, thereby enabling the correlation of proton-proton through-space and through-bond connectivities with the chemical shift of the directly bonded 15N atom. These heteronuclear experiments were crucial for the sequential assignment as the proton chemical shift dispersion of the Ner protein is limited and substantial overlap precluded unambiguous assignment of the homonuclear spectra in several cases. From a qualitative interpretation of the NOE data involving the NH, C alpha H, and C beta H protons, it is shown that Ner is composed of five helices extending from residues 11 to 22, 27 to 34, 38 to 45, 50 to 60, and 63 to 73.

Total assignment of the 1H and 13C NMR spectra of phenanthro[9,10‐b]thiophene: Concerted use of two‐dimensional NMR techniques

AbstractThe 1H and 13C NMR spectra of phenanthro[9,10‐b]thiophene were totally assigned using a combination of twodimensional NMR techniques. Direct hetcronuclear correlations were established using heteronuclear chemical shift correlation with semi‐selective proton decoupling. Two methods were employed to establish the identity of vicinal neighboring protons: heteronuclear relayed coherence transfer and low‐pass J‐filtered heteronuclear relayed coherence transfer. The versatilities of the two techniques were compared. Quaternary carbon resonance assignments and the orientations of individual spin systems relative to one another were accomplished using the proton‐detected long‐range heteronuclear multiple quantum coherence experiment (HMBC). Key long‐range inter‐ring proton homonuclear spin couplings served to confirm the orientations of the proton spin systems.