Hydration effects on low-frequency protein dynamics observed in simulated neutron scattering spectra
Yasumasa Joti 1, Hiroshi Nakagawa 2, Mikio Kataoka 3 and Akio Kitao 1*
1 University of Tokyo
2 JAEA
3 NAIST
* To whom correspondence should be addressed. E-mail: kitao{at}iam.u-tokyo.ac.jp.
Submitted on July 23, 2007
Revised on September 18, 2007
Accepted on 31 December 2007
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Abstract |
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Hydration effects on protein dynamics were investigated by comparing the frequency dependence of the calculated neutron scattering spectra between full and minimal hydration states at temperatures between 100 and 300 K. The protein boson peak is observed in the frequency range 1-4 meV at 100 K in both states. The peak frequency in the minimal hydration state shifts to lower than that in the full hydration state. Protein motions with frequency higher than 4 meV were shown to undergo almost harmonic motion in both states at all temperatures simulated, whereas those with frequency lower than 1 meV dominate the total fluctuations above 220 K and contribute to the origin of the glass-like transition. At 300 K, the boson peak becomes buried in the quasi-elastic contributions in the full hydration state, but is still observed in the minimal hydration state. The boson peak is observed when protein dynamics are trapped within a local minimum of its energy surface. Protein motions, which contribute to the boson peak, are distributed throughout the whole protein. Fine structure of the dynamics structure factor is expected to be detected by the experiment if a high resolution instrument (< ~20 µeV) is developed in the near future.
Key Words:
boson peak, hydration effect, molecular dynamics simulation, neutron scattering, protein dynamics
