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Updated: Jan 9, 2026

Study of Protein Dynamics via Neutron Spin Echo Spectroscopy
Published on: April 13, 2022
Dynamics of protein-water mixtures: insight from combined 1H spin-lattice and spin-spin relaxation studies of
Kahinga Kamau1, Elzbieta Masiewicz1, Pedro José Sebastião2
1Department of Physics and Biophysics, University of Warmia and Mazury in Olsztyn, Oczapowskiego 4, 10-719 Olsztyn, Poland.
Abstract:
Aiming to reveal the dynamical properties of highly concentrated protein-water systems and validating models of motion, 1H spin-lattice and spin-spin relaxation experiments were performed for myoglobin - H2O (40 % wt. of myoglobin) mixture versus temperature, from 268 K to 310 K. The spin-lattice relaxation studies were conducted using Fast Field Cycling (FFC) NMR relaxometry, in the frequency range from 10 kHz to 20 MHz. The comprehensive set of relaxation data was interpreted in terms of a superposition of relaxation contributions expressed in terms of Lorentzian spectral densities and corresponding to the time scales of the order of 10-6 s, 10-8-10-7 s and 10-9-10-8 s. The model was validated against the 1H spin-spin relaxation data obtained from Time Domain (TD) NMR experiments at 18.5 MHz. The studies were complemented by 1H spin-lattice (FFC NMR and TD NMR) and spin-spin (TD NMR) relaxation experiments for myoglobin - D2O (40 % wt. of myoglobin) mixture. Bi-exponential spin-spin relaxation processes were observed for both myoglobin - H2O and myoglobin - D2O mixtures. A thorough comparison of the spin-lattice relaxation and spin-spin relaxation rates (both components) for the H2O and D2O containing mixtures led to the conclusion that the fast component of the spin-spin relaxation process originates from the pool of 1H nuclei of myoglobin and is associated with slow dynamics of the protein, while the slow component of the spin-spin relaxation is a counterpart of the spin-lattice relaxation process (observed by FFC NMR and TD NMR) and they both reflect the dynamics of water molecules strongly bound to myoglobin (for myoglobin - H2O) and a similar dynamics of myoglobin (for myoglobin - D2O).
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