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#NOESY

3 public questions tagged with this topic.

NMRSpectroscopy

What is observed in NOESY for a folded helical peptide?

Folded helical peptide displays characteristic NOESY pattern with dominant sequential amide-amide connectivities Ni to Ni+1 along backbone, reflecting regular short NH-NH distances in helical geometry. Additionally, medium-range NOEs like alpha to amide i to i+3 and alpha to beta i to i+3 appear, while long-range NOEs are sparse. Observing strong Ni-Ni+1 ladder with these medium contacts, combined with small coupling constants and upfield C-alpha chemical shift index, indicates stable helix. Such pattern is absent in random coil, confirming ordered helical conformation in aqueous solution.

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

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NMRSpectroscopy

Which 2D-NMR method reveals through-space interactions?

Two-dimensional NOESY relies on dipole-dipole cross-relaxation transferring magnetization between nuclei close in space, typically within 0.5 nanometer, regardless of covalent bonding. COSY and TOCSY instead transfer coherence via scalar J-coupling through bonds, mapping covalent spin systems. HSQC correlates directly bonded heteronuclei like proton to carbon 13 or nitrogen 15. For biomolecular three-dimensional architecture, through-space contacts are essential because tertiary folding brings distant residues into proximity. NOESY distance restraints enable calculation of protein and RNA solution structures, distinguishing folded from unfolded states reliably.

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

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NMRSpectroscopy

Which NOE peak pattern suggests α-helical structure?

In alpha helix, periodicity 3.6 residues per turn places successive amide protons approximately 2.8 angstroms apart, enabling strong dipole-dipole cross-relaxation observed as intense sequential dNN cross-peaks in two-dimensional NOESY. Continuous chain of Ni to Ni+1 NH-NH contacts along entire sequence is hallmark of helix, often accompanied by medium-range i to i+3 and i to i+4 contacts. Beta sheets show different pattern with strong CαH-NH and long-range interstrand contacts. Recognizing continuous amide-amide NOE ladder confirms helical folding in synthetic and natural peptides.

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

View Details