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#protein NMR

3 public questions tagged with this topic.

NMRSpectroscopy

Which type of NMR experiment uses H/D exchange?

Hydrogen-deuterium exchange monitored by NMR quantifies protection of amide protons over time after dilution into heavy water, reporting structural stability and solvent accessibility. COSY and TOCSY elucidate covalent spin systems through scalar coupling, while NOESY reports through-space contacts for folding. Specific H/D exchange NMR experiment records sequential proton or 15N-HSQC spectra measuring intensity decay of NH peaks, extracting exchange rates and protection factors. This method maps stable versus flexible regions, validates secondary structure, and probes ligand-induced rigidification, widely used in protein folding, epitope mapping, and membrane protein studies.

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

A 30-residue helical peptide in NMR shows:

Hydrogen bonds in alpha helix link carbonyl oxygen of residue i to amide proton of residue i+4, shielding amides from solvent and reducing exchange with deuterium. In a 30-residue stable helix, many NH groups exhibit protection, exchanging slowly over hours versus unstructured coils exchanging within seconds to minutes. Observing slow NH to ND exchange after transferring peptide into D2O, evidenced by persistent amide resonances in successive proton spectra, indicates hydrogen-bonded, folded structure. This slow exchange corroborates NOE ladder and coupling constant data for helix stabilization and core packing.

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

In D₂O exchange, which proton gets replaced?

Labile protons attached to nitrogen or oxygen exchange with deuterium in D2O through acid-base catalyzed mechanisms. Amide backbone NH in proteins exchanges at rates modulated by hydrogen bonding, solvent exposure, and structural stability, leading to disappearance of corresponding peak in proton spectrum after dissolution in deuterated solvent. Carbon-bound protons including aromatic, aliphatic, and C-alpha hydrogens are kinetically stable and remain visible. Monitoring amide signal decay therefore informs on protected secondary structures, membrane protein topology, and conformational dynamics relevant to folding and allosteric regulation.

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