Myoglobin neutron scattering

Figure 4.2. Temperature dependence of the rate constant of electron transfer (Icet) in myoglobin modified covalently by donor-acceptor groups (a) and the deviation of various dynamic quantities from normal harmonic behaviour obtained by molecular dynamic simulation, inelastic neutron scattering, MOssbauer spectroscopy and spectral broadening analysis (b). (Likhtenshtein et al., 2000). Reproduced with permission.

The protein properties include (1) motions of several proteins monitored by ESR spin labels (Belonogova et al., 1978, 1979 Likhtenshtein, 1976 Steinhoff et al., 1989) and Mossbauer labels (Belonogova et al., 1979 Likhtenshtein, 1976) (2) temperature dependence of neutron scattering for myoglobin (Cusack, 1989 Doster et al., 1989) (3) Mossbauer spectra (Parak et al., 1988) and RSMR spectra (Goldanskii and Krupyanskii, 1989) of myoglobin and (4) mechanical properties of lysozyme crystals (Morozov and Gevorkyan, 1985 Morozov et al., 1988). 

The picosecond internal dynamics of myoglobin was explored by measuring inelastic neutron scattering by Smith et al. [25]. At low temperatures they found the dynamics to be harmonic while at higher temperatures a considerable quasielastic scattering was detected. Agreement between the experimentally observed spectra and that calculated from molecular dynamics simulations also showed evidence for restriction of the conformational space sampled at 80 K relative to 300 K. On the basis of these results it was concluded that the protein is trapped in local minima at low temperatures in accord with the multiple substate model suggested by low temperature flash photolysis experiments and previous molecular dynamics simulations. Comparison of atomic fluctuation data sets collected at both 325 K and 80 K confirms that the room temperature... 

Doster, W., and Gebhardt, R. (2003) High pressure-unfolding of myoglobin studied by dynamic neutron scattering, Chem. Phys. 292, 383-387... 

APD = avalanche photodiode detector APS = advanced photon source DFT = density functional theory ESRF = European synchrotron radiation facility HOPE = high-density polyethylene IR = infrared INS = inelastic neutron scattering KED = kinetic energy distribution Mb = myoglobin NIS = nuclear inelastic scattering NRVS = nuclear resonance vibrational spectroscopy NRIXS = nuclear resonant inelastic X-ray scattering OEP = octaethylporphyrin sGC = soluble guanylate cyclase VDOS = vibrational density of states. 

Settles M, Doster W Anomalous diffusion of adsorbed water A neutron scattering study of hydrated myoglobin. Farar/ay Dwcmm. 1996, 103 269-279. 

Doster W, Cusack S, Petty W Dynamical transition of myoglobin revealed by inelastic neutron scattering. Nature 1989, 337 754—756. 

Fig. 19. Dependence of 7(0) on the volume fraction of HjO and H20 present in neutron scattering experiments. The vertical scales in (a), (b) and (c) are not to the same scale, (a) The I(O) values for myoglobin in 10 different contrasts are a linear function of the solvent scattering density [44]. This is the usual result of neutron contrast variation and indicates the monodispersity of the sample. The match-point corresponds to the so-called dry unhydrated volume of the protein. Typical Stuhrmann plots for proteins and glycoproteins are exempUfied in Fig. 21. (b) The values tor ferritin in 10 different... 

Equation (31) assumes an existence of two kinds of molecules showing quite different reorientational dynamics in the considered time interval. The water molecules with strong retardation of rotational motion and with broad distribution of relaxation times (low value of P) should be considered strongly bound. Such kind of water molecules with similar low values of the stretching exponent were observed in neutron-scattering experiment for combined rotational-translational motion of water in hydrated myoglobin (P 0.3) [643] and in simulations of water near mica surface (P k 0.25) [652]. Those water molecules, which show simple one-term exponential relaxation, like in the bulk, should be considered as weakly bound. Fractions of these two kinds of molecules ((1 - a) and a, respectively) should depend on the hydration level. Note, that weakly bound water molecules with Debye rotational relaxation were not distinguished in other simulation studies [610, 644]. 

R. J. Loncharich, B. R. Brooks, Temperature dependence of dynamics of hydrated myoglobin Comparison of force field calculations with neutron scattering data, J. Mol. Biol. 215 (1990) 439-455. 

J. Smith, K. Kuczera, M. Karplus, Dynamics of myoglobin Comparison of simulation results with neutron scattering spectra, Proc. Natl. Acad. Sci. U.S.A. 87 (1990) 1601-1605. 

Neutron experiments were first made on haemoglobin [98,99,147,166,167] and were extended to myoglobin [44,168], lysozyme [169] and catalase [170] as models of typical globular proteins. In parallel with X-ray scattering, the haemoglobin work (mainly in H20) identified a conformational change between the oxy- and deoxy-forms which was reflected in an difference of 0.054 nm in H20 buffers. Scattering curve comparisons to <2 = 3 nm with the crystal structures verified this. 

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