Power Point Slides

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2. Topic: Nuclear Magnetic Resonance
Presented By:
Mohsin Shad 2013-bc-005
Presented To:
Dr.Muhammad Tayyab
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3. Nuclear Magnetic Resonance
 NMR Spectroscopy is one of the powerful and
theoretically complex analytical techniques used to
determine the structure of organic compounds
It allows the characterization of a very small amount of
sample (10mg), and does not destroy the sample
It provide vast information about a molecule's structure
It is used to confirm a complicated molecule's structure by
conjunction with other types of spectroscopy and chemical
analysis .
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4. Principle of NMR
The principle of NMR comes from the spin of nucleus
Nuclear spins generates magnetic field without applied
an external magnetic field
The nuclear spins are random in directions
When an external magnetic field (B0), is present the nuclei
align themselves either with or against field of the external
magnet.
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5. The emitted radio frequency is directly proportional
to the strength of the applied field.
V= 𝛾𝐵 𝑂/2𝜋
B0 = external magnetic field experienced by proton
γ= magnetogyric ratio (the ratio between nuclear
magnetic momentum and angular momentum)
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6. NMR Instrumentation
There are seven parts of NMR Spectroscopy which are
described below:
1. Sample Holder
2. Permanent Magnet
3. Magnetic Coils
4. Sweep Generator
5. Radio Frequency Transmitters
6. Radio Frequency Receiver
7. Read out Systems
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7.  Sample Holder:
Glass tube which is 8.5cm longer and 0.3cm in
diameter.
 Permanent Magnet:
It provides homogenous magnetic field at 60-100 MHz
 Magnetic Coils:
These coils induce magnetic field when current flow
through them.
 Sweep Generator:
To produce an equal amount of magnetic field pass
through the sample
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8.  Radio Frequency Transmitters:
Radio Frequency Transmitters that produces a
shorts powerful pulse of radio waves.
 Radio Frequency Receiver:
Radio Frequency Receiver that detects receiver radio
frequencies emitted as nuclei relaxes of lower energy
level.
 Read out Systems:
A computer that analysis and record the data.
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9. Chemical Shift Scale
A chemical shift is defined as the difference in
parts per million (ppm) between the resonance
frequency of the observed proton and that of the
tetramethylsilane (TMS) hydrogen
 Chemical Shift Scale is also Called d Scale
It does not depend on the magnetic field strength.
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10. How We Measure The Chemical Shift ?
Measure the absorbance frequency of NMR
standard
Measure the frequency of our sample
Subtract the sample frequency from that of the
standard
Finally divided by the frequency of the standard
This gives a number called the “chemical shift
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11. Types of NMR
There are several types of NMR spectra, which
depend upon:
 The kind of instrument used
 The type of nucleus involved
 The physical state of the sample
 The environment of the analytic nucleus
 The purpose of the data collection
Most NMR spectra can be categorized as either
wide line or high resolution. 11

12. Wide-Line spectra:
The spectra in which the bandwidth of the source of the
lines is large enough so that the fine structure due to
chemical environment is obscured. A single peak is
associated with each species
High-Resolution Spectra:
Most NMR spectra are high resolution and are
collected by instruments capable of differentiating
between very small frequency differences of 0.01 ppm or
less. But in the higher resolution spectrum
Two of the three peaks can be resolved into additional
peaks.
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13. NMR Applications
 Some of the applications of NMR spectroscopy are listed
below:
 It determine the bio macromolecules in aqueous solutions
under near physiological conditions.
 It determine the residual structures of unfolded proteins
and the structures of folding intermediates
 It determine the chemical properties of functional groups
in bio macromolecules
 such as the ionization states of ionizable groups at the
active sites of enzymes.
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14. Advantages of NMR
 With a suitable computer apparatus we can calculate the
whole 3D structure of proteins and enzymes.
 The motion of segments (domains) can be examined.
 This method is able to lead us for the observation of
chemical kinetics.
 We can investigate the dielectric constant, the polarity and
any other properties of the solvent or some added
material.
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15. • A powerful tool in the research of polymer chemistry
and physics
• A matured technique for chemical identification and
conformational analysis of chemicals whether
synthetic or natural.
• Solid state NMR has the potential for determining
atomic-resolution structures of domains of
membrane proteins in their native membrane
environments, including those with bound ligands
• A power tool for the detection of interior water and
its interaction with bio macromolecules.
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16. Disadvantages of NMR
 This is good for more accurate determination of the structure,
but not for the availability of higher molecular weight.
 The resolving power of NMR is less than some other type of
experiments (e.g. X-RAY CRYSTALLOGRAPHY) since the
information got from the same material is much more complex.
 Unfortunately we are just able to determine the degree of
probability of being of protein segment in the given
conformation.
 The cost of the experimental implementation is increasing with
the higher strength and the complexity of determination.
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17. NMR Application in Enzymology
 NMR is applied :
 To the study of conformational dynamic processes in
enzymes
 To study the biological activities of enzymes
 To study the exchange of more open or flexible
conformational states with more closed or constrained
states
 NMR spin relaxation studies of the enzymes ribonuclease
HI from mesophilic and thermophilic bacteria
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