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NOE

NOEs between nuclei are often exploited to demonstrate their spatial proximity, as described in the final section. It is possible to obtain decoupled NMR spectra without the complications of the NOE, by confining the decoupling irradiation to the period of the FID alone, and then waiting for 10 x before... [Pg.1444]

Wlien is very short, which is almost always true with nuclei having/> 1/2, the dipolar contribution to relaxation will be negligible and, hence, there will be no contributions to the integral from either NOE or saturation. However, resonances more than about 1 kHz wide may lose intensify simply because part of the FID will be lost before it can be digitized, and resonances more than 10 kHz wide may be lost altogether. It is also hard to correct for minor baseline distortions when the peaks themselves are very broad. [Pg.1444]

Figure Bl.11.14. NOE-difFerence spectrum (see the text) of aspirin, with pre-saturation at the methyl resonance, proving that the right-hand confomration is dommant. Figure Bl.11.14. NOE-difFerence spectrum (see the text) of aspirin, with pre-saturation at the methyl resonance, proving that the right-hand confomration is dommant.
NOE-difFerence spectroscopy is particularly valuable for distinguishing stereoisomers, for it relies solely on intemuclear distances, and thus avoids any problems of ambiguity or absence associated with couplings. With smallish molecules, it is best carried out in the above 1D maimer, because 2 s are necessary for tire transmission of the NOE. The transmission process becomes more efficient with large molecules and is almost optimal for proteins. However, problems can occur with molecules of intemiediate size [3f]. A 2D version of the NOE-difference experiment exists, called NOESY. [Pg.1463]

Bax A and Davis D G 1985 Practical aspects of two-dimensional transverse NOE spectroscopy J. Magn. Reson. 63 207-13... [Pg.1464]

Besides measuring and T2 for nuclei such as C or N, relaxation studies for these nuclei also include measurements of the NOE factor, cf equation B 1.13.6. Knowing the (pj) and the steady-state NOE... [Pg.1510]

The interval between the second and third pulse is called the mixing time, during which the spins evolve according to the multiple-spin version of equation B 1.13.2 and equation B 1.13.3 and the NOE builds up. The final pulse converts the longitudinal magnetizations, present at the end of the mixing time, into detectable transverse components. The detection of the FID is followed by a recycle delay, during which the equilibrium... [Pg.1510]

Small molecules in low viscosity solutions have, typically, rotational correlation times of a few tens of picoseconds, which means that the extreme narrowing conditions usually prevail. As a consequence, the interpretation of certain relaxation parameters, such as carbon-13 and NOE for proton-bearing carbons, is very simple. Basically, tlie DCC for a directly bonded CH pair can be assumed to be known and the experiments yield a value of the correlation time, t. One interesting application of the measurement of is to follow its variation with the site in the molecule (motional anisotropy), with temperature (the correlation... [Pg.1513]

Kovacs H, Bagley S and Kowalewski J 1989 Motional properties of two disaccharides in solutions as studied by carbon-13 relaxation and NOE outside of the extreme narrowing region J. Magn. Reson. 85 530 1... [Pg.1518]

When using XOH signals as restrain ts, choose the distance between the nonbonded atoms. A typical distance is about 4 to 5 Angstroms. A typical force constant is 0..5 to. 5.0 kcal/A-, depending on the flexibdity ofthe rest of the molecule and the strength of the NOE signal. [Pg.82]

The amount of computation necessary to try many conformers can be greatly reduced if a portion of the structure is known. One way to determine a portion of the structure experimentally is to obtain some of the internuclear distances from two-dimensional NMR experiments, as predicted by the nuclear Over-hauser effect (NOE). Once a set of distances are determined, they can be used as constraints within a conformation search. This has been particularly effective for predicting protein structure since it is very difficult to obtain crystallographic structures of proteins. It is also possible to define distance constraints based on the average bond lengths and angles, if we assume these are fairly rigid while all conformations are accessible. [Pg.185]

You can often use experimental data, such as Nuclear Overhauser Effect (NOE) signals from 2D NMR studies, as restraints. NOE signals give distances between pairs of hydrogens in a molecule. Use these distances to limit distances during a molecular mechanics geometry optimization or molecular dynamics calculation. Information on dihedral angles, deduced from NMR, can also limit a conformational search. [Pg.82]

The addition of paramagnetic species, such as the metal ions Cu ", Mn, or CF", can have dramatic effects on both the observed spectmm and the relaxation behavior of a molecule. The added ion reduces nuclear relaxation times, and permitting more rapid data collection. In addition, faster relaxation rates minimize NOE effects in the spectra, which can be useful in obtaining quantitative intensity data. The most widely used reagent for this purpose is chromium acetylacetonate [13681 -82-8] known as Cr(acac)2. Practically speaking, the use of such reagents requires care, because at... [Pg.403]

NOE difference spectroscopy is used to identify short, throughspace interactions and measure these interactions to an upper limit of about... [Pg.404]

Decoupling has two effects all multiplets are coUapsed into singlets, one for each nonequivalent atom and the transfer of NOE from the excited H to... [Pg.404]

J. M. Lerat, in P. Louvet, P. Noe, and Soubbaramayer, eds.. Proceedings of the Second Workshop on Separation Phenomena in Eiquids and Gases, Versailles,... [Pg.199]

Another technique often used to examine the stmcture of double-heUcal oligonucleotides is two-dimensional nmr spectroscopy (see AfAGNETiC SPIN resonance). This method rehes on measurement of the nuclear Overhauser effects (NOEs) through space to determine the distances between protons (6). The stmcture of an oligonucleotide may be determined theoretically from a set of iaterproton distances. As a result of the complexities of the experiment and data analysis, the quality of the stmctural information obtained is debated. However, nmr spectroscopy does provide information pertaining to the stmcture of DNA ia solution and can serve as a complement to the stmctural information provided by crystallographic analysis. [Pg.250]


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A One-Dimensional Experiment Utilizing the NOE

A,P-Unsaturated ketone NOE experiments

Confirmed by NOE measurements

Criegee-Corey-Noe

DPFGSE-NOE

Decoupled, NOE (Double Resonance) and COSY Spectra

Derivation of the Equations Related to NOE

Equilibrium NOE

Exchange-transferred NOE (etNOE)

FACTORS AFFECTING nOe

Heteronuclear NOE

Heteronuclear nOe Spectroscopy (HOESY)

Homonuclear Difference NOE The Test for Proximity

Homonuclear NOE

Homonuclear NOE experiments

ID Transient NOE using DPFGSE

Influence of Heteronuclear NOE

Long-range NOE

Long-range NOE correlations

MECHANISM OF nOe

Measurement of NOE Enhanced Coupled 13C NMR Spectra

Measurements of NOE

Medium and Long-Range NOE Correlations

Mniopetal E synthesis NOE experiments of IMDA

N Relaxation and NOE Factors

NMR spectra proton coupled, NOE

NMR spectroscopy transferred NOE

NOE (nuclear Overhauser

NOE (nuclear Overhauser effect

NOE (nuclear Overhauser effect difference spectra

NOE (nuclear Overhauser effect suppression

NOE Refinement

NOE Spectroscopy (NOESY)

NOE Spectroscopy and 3-D Structure

NOE and Chemical Exchange

NOE constraints

NOE contacts

NOE correlated spectroscopy

NOE correlation spectroscopy

NOE data

NOE difference

NOE difference measurements

NOE difference spectrometry

NOE difference spectroscopy

NOE difference spectrum

NOE distances

NOE effects

NOE enhancement

NOE enhancement factors

NOE experiment of abscisic acid

NOE experiment of teucrolivin

NOE experiments

NOE experiments of IMDA

NOE factor

NOE in the rotating frame (ROE)

NOE intensities

NOE interactions

NOE kinetics

NOE matching

NOE measurements

NOE spectroscopy

NOE spectrum

NOE studies

NOE values

NOE-NOESY

NOE-difference experiments

NOE-enhanced proton-coupled

NOE-enhanced proton-coupled spectrum

NOE-restrained molecular dynamics

Negative NOE

Nuclear Overhauser Effect (NOE) Difference Spectroscopy

Nuclear Overhauser effect NOE difference

Nuclear Overhauser enhancement (nOe

Positive NOE

Relayed nOe Experiments

Rotating-frame NOE

Spin-lattice relaxation influence on NOE

Steady state NOE

Steady state NOE in paramagnetic compounds

Steady state NOE in real life

Steady-state NOE measuring

Stepwise Solution of the Combined Dipolar and NOE Equations

Teucrolivin NOE experiments

Teupestalin NOE experiments

The Homonuclear Nuclear Overhauser Effect (NOE)

The NOE Difference Experiment

The NOE Through-Space Interactions between Protons

The Nuclear Overhauser Effect (NOE)

Transfer NOE

Transfer NOE experiments

Transferred NOE

Transferred NOE technique

Transient NOE

Truncated NOE

Truncated driven NOE

Two-Dimensional Heteronuclear NOE (HOESY)

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