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Nuclear magnetic resonance 1

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NMR use in medical science as MRI, Molecular structure determination. Solution structure of proteins and peptides.
Magnetic resonance imaging. Identification of protein-protein interaction sites is crucial for understanding the basis of molecular recognition.

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Nuclear magnetic resonance 1

  1. 1. By -Vivek singh King George’s Medical University Lucknow.
  2. 2.  Introduction  Principle and instrumentation  Resonance( Flipping)  Population density  The chemical shift and shielding  Magnetic anisotropy  Spin-spin splitting( origin and n+1 rule)  Application
  3. 3.  Nuclei studied by NMR techniques.  NMR gives information the no. of magnetically distinct atoms.  Radiofrequencies have low energy; only cause nuclear spin[ nmr].
  4. 4.  The nucleus has magnetic moment generated by its charge & spin.  A hydrogen nuclear may have clockwise [+1/2] or counterclockwise[-1/2].  Spin state +1/2 has lower energy and aligned with magnetic field; -1/2 higher energy opposite to magnetic field.  In NMR, entities are nuclear magnetic spins which populate energy level a/c to quantum chemical rule.
  5. 5.  A slight excess nuclei in lower energy spin state.  Magnitude of this difference calculated by BOLTZMANN DISTRIBUTION LAW.  Saturation achieved if power of RADIOFREQENCY signal is too high.
  6. 6.  Electron surrounds the proton produces magnetic field which oppose the field DIAMAGNETIC SHIELDING.  Standard reference is TETERAMETHYLSILANE[TMS]-proton are more shielded than other compounds.  The CHEMICAL SHIFT is amount by which proton resonance is shifted from TMS.
  7. 7.  Different kinds of protons come at different chemical shifts.shown below is a chart of some common kinds of protons that appear in delta scale. ppm TMS CH3CH3 RONR2 CH3OCH3 RO HR R R HH RO Ph CH3 HR Cl CH3 Ph OH OH R NH R Upfieldregion of the spectrum Downfieldregion of the spectrum TMS = Me Si Me Me Me 012345678910 CH3HO (R)
  8. 8.  Area under each peak is proportional to no. of hydrogens generating that peak.  Eletronegativity.  Hybridisation.  Acidic and exchangeable proton; hydrogen – bonding.
  9. 9.  Downfield= deshielded molecule  Up field=shielded molecule
  10. 10.  Example- benzene;  It placed in magnetic field, pie electron of aromatic ring are induced to circulate around ring.  Circulation of electron is called ring current(shielded region).  Moving electrons generate magnetic field much like generated in the loop of wire.  A proton attached to benzene ring is influenced by three magnetic field(more deshielded hydrogen).
  11. 11.  If a proton has n neighbouring protons that are equivalent, that proton will split into n+1 lines. no. of neighbors relative intensities pattern 1 1 1 1 2 1 1 3 3 1 1 4 6 4 1 1 5 10 10 5 1 1 6 15 20 15 6 1 0 1 2 3 4 5 6 singlet (s) doublet (d) triplet (t) quartet (q) pentet sextet septet example H C C H H C C H H H C C H H H H C CC H H H H H C CC H H HH H H C CC H H H H H H
  12. 12.  It arises because hydrogens on adjacent carbon atoms can SENSE one another.  n+1 rule-each type of proton senses the no. of equivalent proton on the carbon atoms next to the one to which it is bonded and its resonance peak splits into n+1 components. C C HBHA HA HB HA is split into tw o lines because it feels the magnetic field of H B. HB is split into tw o lines because it feels the magnetic field of H A. For this line, H B is lined up with the magnetic field (adds to theoverall magnetic field, so the line comes at higher frequency) For this line, H B is lined up against the magnetic field (subtracts from the overall magnetic field, so the line comes at low er frequency)
  13. 13.  When there is more than one proton splitting a neighbouring proton, we get more lines. Consider the molecule shown below where we have 2 protons on one carbon and one proton on another. C C HBHA HA' HA + HA' HB HA and H A' appear at the same chemical shif t because they are in identical environments They are also split into tw o lines (called a doublet) because they f eel the magnetic f ield of H B. HB is split into three lines because it feels the magnetic f ield of HA and HA' Note that the signal produced by HA + HA' is tw ice the size of that produced by HB
  14. 14.  Molecular structure determination.  Solution structure of protiens and peptides.  Magnetic resonance imaging.  Identification of protien-protien interaction sites is crucial for understanding the basis of molecular recognition.
  • AqsaAhmed19

    Oct. 29, 2018
  • sabaubaid

    Aug. 18, 2017
  • viveksingh9849

    Jun. 29, 2017

NMR use in medical science as MRI, Molecular structure determination. Solution structure of proteins and peptides. Magnetic resonance imaging. Identification of protein-protein interaction sites is crucial for understanding the basis of molecular recognition.

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