2. CONTENT
• NOE(Nuclear overhauser effect)
• NOESY(nucleae overhauser effect spectroscopy)
• NOESY experiment
• Properties of NOESY
• NOESY application
• 2D-NOESY spectra of small molecule
• 2D NMR
• Types of 2D NMR
• PRINCIPL
3. NOE(NUCLEAR OVERHAUSER EFFECT)
• The NOE is of great value in studying the molecular geometry
of the compounds.
• It tell whether the two protons are in close proximity within the
molecules or not.
• An important consequence of this effect is that the line
intensities observed in the normal spectrum may not be the
same as in the decoupled spectrum.
4. DIFINITION OF
NOESY
• The NOESY is a 2D nmr spectroscopic method used to identify
nuclear spins undergoing class-relaxation and to measure their
cross-relaxation rates.
• NOESY is an important tool to identify stereochemistry of
protein and other biomolecules in solution.
• NOESY is a two-dimensional NMR spectroscopy method.
5. NOESY EXPERIMENT
• The NOESY experiment can also be performed in a one
dimensional fashion by pre-selected nuclei giving a large ,
negative signal while neighboring nuclei are identified by
weaker ,positive signal.this only reveals which peak have
measurable NOEs to the resonance of interest but takes much
less time than the full 2D experiment.
6. PROPERTIES OF NOESY
• Cross peak between protons which are in close spatial
proximity.
• For short enough mixing times (small molecule 400-800ms,
large molecule 100-200ms) the cross peak intensity is
proportional to the cross relaxation rate and thus to r.
• For small molecule noe and chemical exchange will give cross
of opposite sign and can be distinguished.
• As sequence is identical to DQF-COSY, coupling can cause
artefacts in spectrum.
7. APPLICATION
• One application of NOESY is in the study of large biomolecules
such as in protein NMR, which can often be assigned using
sequential walking.
8. 2D-NOESY SPECTRA 0F SMALL
MOLECULES
• The noesy spectrum uses the nuclear overhauser effect(NOE) to
provide information about which proton(typically) resonance
are from protons which are close together in space.
• This is distinct from COSY-type spectra which use the J-
coupling interation to report on which proton resonances are
located on the same or adjacent carbon nuclei.
9. 2D NMR
• The first 2D experiment was proposed by jean jenner.
• 2D NMR is set of nuclear magnetic resonance spectroscopy
methods which give data plotted in a space defined by to
frequency axes rather than one.
• 2D NMR spectra provide more information about a molecule
than one-dimensional NMR spectra.
• 1D=one time variable,one intensity variable
• 2D=two time variables, two time intensity variable..
10. TYPES OF 2D NMR
• Homonuclear experiment: in this experiment we provide two
frequency to same nuclei in sample. i.e.H-H Correlation
spectroscopy (cosy)actually in it we basically see homonuclear
connectivity between same nuclei.
• Hectronuclear experiment: in this experiment we provides two
frequency to different nuclei in the sample.i.e. H-C
Hectronuclear Correlation(HETCOR).
11. PRINCIPLE OF 2D NMR
2D NMR is nuclear magnetic resonance spectroscopy in which we
provide a 90 degree pulse to our sample which is placed in uniform
magnetic field then we wait for (oms-5ms) depending upon the
experiment type then again we provide again 90 degree pulse and this
time we measure signal as FID.
As a result we get two FID signals which are plotted with respect to
time domain.
To get a meaningful data, we apply fourier transform program on FIDs
to get frequency.
12. APPLICATION OF 2D NMR
• Two- dimensional NMR lead to the development of chemical
shifts into two dimensional and to resolve overlap of resonance
which enables the correlation of intracting nuclei to be
determined.
• Two dimensional NMR can be applied to complex spectra which
are difficult to analyzed by conventional methods.
• COSY identifies pair of protons which are coupled to each
other.
• The HETCOR spectra used to detect directly bounded 13C-1H.
13. LIMIT OF NMR
• Limited to measurement of nucleus with magnetic moment.
• Less sensitive than other spectroscopic and chromatographic
analytical methods.
• No response in ionic state.
• Paramagnetic component broaden NMR lines which reduces
NMR signal and sensitivity.
