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 dynami
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.
