Kinetic isotope effects for fast deuterium and proton exchange rates

Printer-friendly version

Kinetic isotope effects for fast deuterium and proton exchange rates, Phys. Chem. Chem. Phys., 2016,18, 10144-10151

 

In the parlance of magnetic resonance, chemical exchange is a process where a nucleus undergoes a change of its environment. The determination of the exchange rates of labile protons can provide valuable insight into both structural and dynamic aspects of a wide range of molecules, such as the opening of basepairs in nucleic acids and protection factors in protein–ligand complexes. In this paper, we shall focus on measurements of D–D exchange rates kD and their comparison with H–H exchange rates kH in tryptophan. The knowledge of kinetic isotope effects, i.e., of the ratio kH/kD that expresses the reduction of D–D exchange rates kD compared to H–H exchange rates kH, may contribute to the characterization of reaction mechanisms. The kinetic isotope effect can give insight into the stability of hydrogenbonded secondary structures in biomolecules. In this work, we shall consider exchange processes involving labile DN deuterons and HN protons that are covalently bound to the nitrogen atom in the indole ring of tryptophan.

 

 

We have adapted our method that was originally designed for measuring fast H–H exchange rates kH to the study of D–D exchange rates k. In tryptophan in aqueous solution over a range of pH, respectively pD, the kinetic isotope effect, defined as the ratio kH/kD between the H–H and D–D exchange rates, was determined at several temperatures. The dependence of the activation energies on pH provides new insight into the mechanisms of the exchange processes. The results agree with the mechanisms discussed by Englander et al.

 

N'hésitez pas à consulter également le communiqué de presse associé à cet article : Mesurer l’échange de protons !

 

 

Résumé: 

Phys. Chem. Chem. Phys., 2016,18, 10144-10151

 

By monitoring the effect of deuterium decoupling on the decay of transverse 15N magnetization in D–15N spin pairs during multiple-refocusing echo sequences, we have determined fast D–D exchange rates kD and compared them with fast H–H exchange rates kH in tryptophan to determine the kinetic isotope effect as a function of pH and temperature.

Equipe de rattachement 7203: 
Equipe 3
Adresse mail du contact: 
Références: 

Kinetic isotope effects for fast deuterium and proton exchange rates

 

Estel Canet, Daniele Mammoli, Pavel Kaderavek, Philippe Pelupessy

and Geoffrey Bodenhausen

 

Phys. Chem. Chem. Phys., 2016,18, 10144-10151

 

DOI: 10.1039/C5CP07459B