Nuclear Overhauser Effect Method Research Articles

Nuclear magnetic resonance structure-based drug design.

Nuclear magnetic resonance structure-based drug design.

Characterization of N-Acetylcysteine Conjugate in Yellow Urine by Oral Administration of 1,4-Dichloro-2-Nitrobenzene in Rats

The color of urine from rats fed 1,4-dichloro-2-nitrobenzene (DCNB) is a clear yellow than that of urine from control rats. In order to obtain information on the relationship between the yellow color of the urine and its constituents, analyses of the components in the urine from rats fed DCNB were performed by UV, nuclear overhauser effect (NOE) method of 1H-NMR and liquid chromatography (LC)-MS/MS. The urine from the rats fed DCNB had absorbance at a wavelength of 383 nm. Characteristic fragment ions of the N-acetylcysteine conjugates, at m/z 187, were clearly observed in the fragmentation of the precursor ions at m/z 317 ([M-H]-) by LC-MS/MS. And position of the structure was found to be N-acetyl-S-(4-chloro-3-nitrophenyl)-L-cysteine by NOE method. Consequently, in view of the conformity of the major constituent (N-acetylcysteine conjugates), when comparing yellow urine and the metabolite, it is thought that the metabolite formation is attributable to the longer wavelength absorbance of the N-acetyl-S-(4-chloro-3-nitrophenyl)-L-cysteine, as compared to the control urine.

One- and two-dimensional proton NMR studies of cys-102 S-methylated yeast isozyme-1 ferricytochrome c

The effect of S-methylating cysteine-102 (cys-102) (SH----SSCH3) of yeast isozyme-1 (iso-1) ferricytochrome c has been studied using proton NMR spectroscopy. COSY, NOESY, and one-dimensional nuclear Overhauser effect (NOE) difference spectroscopies have all been used. The NMR spectrum of this derivative is very similar to that of native yeast iso-1 ferricytochrome c. The advantage of using the cys-102 S-methylated derivative is that it is unable to spontaneously dimerize in solution, like native iso-1 monomer does. This makes the derivative a simple, ideal protein for long NMR experiments. This work yields many proton resonance assignments for S-methylated yeast iso-1 monomer and confirms all of the assignments for iso-1 monomer that were previously made using only the one-dimensional NOE method.

17] Ligand conformations and ligand-enzyme interactions as studied by the nuclear overhauser effect

Publisher Summary The nuclear Overhauser effect (NOE) has proved to be a powerful tool for the elucidation of molecular structure. Limitations of the NOE method for determining the conformation of a bound ligand result from the assumptions of fixed interproton distances and a single correlation time for all internuclear vectors. In many cases, the validity of these assumptions can be tested by experiment. However, if several bound conformations coexist with different interproton distances, the NOE method will yield a nonlinear average conformation skewed toward those conformations having the shortest interproton distances. Multiple conformations for the bound ligand can usually be detected by observing two or more interproton NOEs that are not mutually consistent with a single conformation. However, a major advance in biological nuclear magnetic resonance (NMR) will be the application of one- and two-dimensional isotope-filtered NOEs along with the selective labeling of the protein and ligand. This methodology will greatly increase the selectivity, identification, and resolution of the NOE experiment and thus our ability to determine the conformations and arrangements of bound ligands and the amino acid environment provided by the protein.

31P Magnetic relaxation studies of yeast transfer RNAPhe

AbstractThe molecular mechanism of thermal unfolding of yeast tRNAPhe in 20 mM NaCl, 1 mM EDTA, and 10 mM MgSO4, pH 7.1 ± 0.1, has been examined by 31P magnetic relaxation and the nuclear Overhauser effect methods at 40.48 MHz in the temperature range of 22.5–80°C. Two partially resolved 31P resonance peaks of yeast tRNAPhe have been found to behave distinctively different in their longitudinal relaxation times. Individual intensities of the two partially resolved peaks have been quantitatively estimated by the use of relaxation data and the nuclear Overhauser effect as a function of temperature. The results of these observations largely support the earlier suggestion by Guéron and Shulman that the high‐ and low‐field parts of the main 31P resonance cluster originate from phosphorus nuclei belonging to the double‐helical and nonhelical regions of the tRNA, respectively. The spin‐lattice relaxation of the phosphorus nucleus has been found to be determined dominantly by the dipolar interaction with the surrounding ribose protons at this observing frequency. Rotational correlation times for the two portions of the ribose‐phosphate backbone of the tRNA have been separately deduced from the quantitative treatment of the 31P nuclear spin‐lattice relaxation times (T1) and the nuclear Overhauser effect. The result indicates that the two portions undergo internal motions at distinctively different rates of 108–1010 sec−1 order in the temperature range of 22.5–80°C, and that the thermal activation of these motions occurs at least in three distinctive steps, i.e., 22.5–31, 31–40, and 40–80°C. The rates of the internal motions and the associated activation energies in respective steps give some insight into the thermo‐induced change of the yeast tRNAPhe structure.