NMR measurements of proton exchange between solvent and peptides and proteins.

Abstract

Scope and limitations of the NMR based methods, equilibration and magnetization transfer, for measuring proton exchange rates of amide protons in peptides and proteins with water protons are discussed. Equilibration is applied to very slow processes detected by hydrogen-deuterium exchange after a solute is dissolved in D2O. Magnetization transfer allows to study moderately rapid processes in H2O. A number of precautions should be undertaken in order to avoid systemic errors inherent in the magnetization transfer method.

Magnetyczny Rezonans Jądrowy W Badaniach Strukturalnych Biomolekuł Na Przykładzie Badania Modelowych Układów Helikalnych

“…Stosowalność tej metody zależy od szybkości wymiany badanych protonów; najczęściej jest ona efektywna w przedziale [0.05s -1 , 20s -1 ]. Ponadto dokładność metody jest limitowana stosunkiem szybkości wymiany (k) do szybkości relaksacji () i jest najbardziej efektywna przy spełnionym warunku k/>0.1 [72].…”

Importance of Structural Tightening, as Opposed to Partially Bound States, in the Determination of Chemical Shift Changes at Noncovalently Bonded Interfaces

“…The required k int and k ex values were determined at pH 4.5. Since the k int values required for the free CE and ligand components correspond to relatively fast rates of exchange (with one exception; see below), these were determined using the method of transfer of saturation from water. , In contrast, k int for the w 7 resonance of CE and all the k ex values of the complex correspond to half-lives for exchange greater than 5 min. These values were therefore conveniently determined by examination of the complex in D 2 O solution, and measuring directly the rate at which the four NHs that were in involved in hydrogen bonds in the complex, and could be monitored, were removed from the spectrum.…”

Methods of peptide conformation studies.

“…At low temperatures (about 0°C) and pH » 3, the exchange process is slow enough to be monitored directly by measuring, in consecutive time intervals, one-dimensional 1 H NMR spectra of deuterated peptide dissolved in H 2 O or of the protonated one, dissolved in D 2 O. At neutral pH the exchange rates are comparable to those of nuclear magnetic longitudi-nal relaxation of the NH peptide protons (about 1 s -1 ) and can be determined from NMR magnetization transfer experiments [22].…”