Neutron scattering lysozyme

Tsai, A.M., Neumann, D.A., and Bell, L.N. (2000) Molecular dynamics of solid-state lysozyme as affected by glycerol and water a neutron scattering study, Biophys. J. 79, 2728-2732. 

Comparison of neutron scattering of lysozyme at 0.07 and 0.20 h (Smith et al., 1987) showed that hydration decreased elastic scattering and increased inelastic scattering between 0.8 and 4.0 cm". This observation is consistent with an increase in the number of low-frequency modes. Normal mode analysis indicates that the lowest frequency mode of lysozyme and the hinge-bending mode fall in this frequency range (Brooks and Karplus, 1985 Bruccoleri et al., 1986 Levitt et al., 1985). Hydration of a protein has little effect on the scattering spectrum, outside of that noted above (Cusack, 1989). 

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). 

Solvent causes a net softening of the local atomic potentials, particularly for exposed sidechain atoms, with a commensurate increase in fluctuation amplitudes. Recent inelastic neutron scattering studies of lysozyme as a function of hydration are in accord with this conclusion.2551 In addition, there are significant localized conformational changes, particularly for sidechains and exposed loop regions, and these, coupled with the increased fluctuations observed in the solvent simulation, may be of functional importance. These points are amplified in Chapt. X, where a thermodynamic analysis of the effect of solvent on the conformational equilibria of a dipeptide model is given. 

The determination of binding and conformational changes leaves the question of the detailed structure of complexes unanswered. At present there is no absolute method for structure determination of protein-surfactant complexes apart from x-ray diffraction, which has only been applied to lysozyme with three bound SDS molecules [49]. X-ray diffraction requires a crystal, so in the case of lysozyme cross-linked triclinic crystals of the protein were soaked in 1.1 M SDS and then transferred to water or a lower concentration (0.35 M) of SDS to allow the protein to refold. It was necessary to use cross-linked crystals to prevent them dissolving when exposed to a high SDS concentration. The resulting denatured-renatured crystals were found to have three SDS molecules within a structure that was similar but not identical to that of native lysosyme. Neutron scattering has been applied in a few cases (see Sec. IX), but this is a model-dependent technique. 

Lerbret A, Affouard Fdr, Hedoux A, Krenzhn S, Siepmann Jr, BeUissent-Funel M-C, Descamps M (2012) How strongly does trehalose interact with lysozyme in the solid state Insights from molecular dynamics simulation and inelastic neutron scattering. J Phys Chem B 116 11103— 11116... 

Svergun et al. [138] studied three proteins lysozyme, Escherichia coli thioredoxin reductase, and E. coli ribonucleotide reductase protein Rl, in aqueous solution, using x-ray and neutron scattering. The density of the water of the first hydiadon shell of these proteins differed from that of bulk water, the average relative deusities were 1.08 0.02, 1.16 0.05, and 1.12 0.06. These experimental values are smaller than those calculated from the packing, 1.22 according to Gerstein and Chothia [137], but still appreciable. 

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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