nclear overhauser effect

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NUCLEAR OVERHAUSER EFFECT

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Nuclear Overhauser Effect : 

Nuclear Overhauser Effect By:-Vrunal V. More M.pharm I(Pharmaceutics) SVERI’S college of pharmacy,pandharpur.

Contents:- : 

Contents:- Introduction Defination

Introduction& Defination:- : 

Introduction& Defination:- The Overhauser Effect is the transfer of spin polarization from one spin population to another via cross-relaxation in nuclear magnetic resonance (NMR) spectroscopy N.O.E.is of great value in studying the molecular geometry of the compounds. It tells whether the two protons are in close proximity within the molecule or not. An important consequence of this effect is that the line intensities observed in the normal spectrum may the same as in the decoupled spectrum.

APPLICATIONS OF NMR : 

APPLICATIONS OF NMR 1.Solution structure The only method for atomic-resolution structure determination of biomacromolecules in aqueous solutions under near physiological conditions or membrane mimeric environments. 2.Molecular dynamics The most powerful technique for quantifying motional properties of biomacromolecules.

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3.Protein folding The most powerful tool for determining the residual structures of unfolded proteins and the structures of folding intermediates . 4. Ionization state The most powerful tool for determining the chemical properties of functional groups in biomacromolecules, such as the ionization states of ionizable groups at the active sites of enzymes .

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5.Weak intermolecular interactions Allowing weak functional interactions between macrobiomolecules (e.g., those with dissociation constants in the micromolar to millimolar range) to be studied, which is not possible with other technologies .

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6.Protein hydration A power tool for the detection of interior water and its interaction with biomacromolecules 7. Hydrogen bonding A unique technique for the DIRECT detection of hydrogen bonding interactions . 8. Drug screening and design Particularly useful for identifying drug leads and determining the conformations of the compounds bound to enzymes, receptors, and other proteins

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8.Native membrane protein 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. 9.Metabolite analysis A very powerful technology for metabolite analysis.

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10.Chemical analysis A matured technique for chemical identification and conformational analysis of chemicals whether synthetic or natural. 11.Material science A powerful tool in the research of polymer chemistry and physics

1.Identification of structural isomers. : 

1.Identification of structural isomers. The distinction between the following isomers can be easily made from their NMR spectra. a b CH3CH2CH2Cl CH3-CH-CH3 I Cl The NMR technique is used to distinguished between cis and trans isomers. Protons in cis and trans isomers have different chemical shift values and different coupling constant

2.Detction of hydrogen bonding. : 

2.Detction of hydrogen bonding. Intermolecular hydrogen bonding shifts the absorption for a concerned proton downfield . The extent of hydrogen bonding varies with the solvent, concentration of solution and the temperature.Intramolecular hydrogen bonding also shifts the absorption downfield.The two types of hydrogen bonding can be distinguished as the intramolecular hydrogen bonding is not conc. dependant.

3.Detection of aromaticity:- : 

3.Detection of aromaticity:- Proton attached to the benzyl,polynuclear and heterocyclic compounds whose Π-electrons follow Huckel rule are extremely deshilded due to the circulation of sextet of Π electron.so signals appear at very downfield.From this aromatic character of a compound can be predicted.

4.Elemental analysis:- : 

4.Elemental analysis:- NMR spectroscopy can be used for the determination of the total conc.of a given magnetic nucleus in a sample.

5.Rate of reactions:- : 

5.Rate of reactions:- An interesting special use of NMR spectroscopy is the study of certain reactions that are too fast for measurement in the sample.

6. Determination of activation of energy:- : 

6. Determination of activation of energy:- This application can be illustrated by taking a well studied example. CH3-C=O-N-CH3-CH3

7.Qualitative analysis. : 

7.Qualitative analysis. The number of main NMR signals should be equal to the number of equivalent protons in the unknown compound.

8.Qantitative analysis:- : 

8.Qantitative analysis:- NMR spectroscopy has been used to determine the molar ratio of the components in mixture.

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