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While most spectroscopic techniques, e.g., nuclear magnetic resonance or dielectric spectroscopy probe macroscopic responses, neutron and with some restrictions also X-ray scattering experiments give unique access to microscopic dynamics at length scales of intermolecular or atomic distances. Only recently, it has become possible to study collective dynamics of planar lipid bilayers using neutron spectroscopy techniques [M.C. Rheinstadter, et al., Phys. Rev. Lett. 93 (2004) 108107]. We determined the dispersion relation of the coherent fast picosecond density fluctuations on nearest-neighbor distances of the phospholipid acyl chains in the gel and in the fluid phases of a DMPC bilayer. The experiments shed light on the evolution of structure and dynamics, and the relation between them, in the range of the gel–fluid main phase transition. The scattering volume restriction for inelastic neutron experiments was overcome by stacking several thousand highly aligned membrane bilayers. By combining different neutron scattering techniques, namely three-axis, backscattering and spin–echo spectroscopy, we present measurements of short and long wavelength collective fluctuations in biomimetic and biological membranes in a large range in momentum and energy transfer, covering time scales from about 0.1 ps to almost 1 μ s and length scales from 3 A to about 0.1 μ m . The neutron backscattering technique gives information about slow molecular dynamics of lipid acyl chains and the ‘membrane-water’, i.e., the water molecules in between the stacked bilayers in the nanosecond time range [M.C. Rheinstadter, et al., Phys. Rev. E 71 (2005) 061908]. The dispersion relations of the long wavelength undulation modes in lipid bilayers with nanosecond relaxation times can be determined by quasielastic reflectometry on spin–echo spectrometers and give direct access to the elasticity parameters of the membranes. [M.C. Rheinstadter, et al., cond-mat/0606114].

Inelastic neutron and X-ray scattering experiments on surfaces and interfaces are a challenging topic in modern physics. Particular interest arises regarding surfaces and interfaces of soft matter and biological systems. We review both neutron and x-ray spectroscopic techniques with view at their applicability to these samples. We discuss the different methods, namely neutron triple-axis, backscattering and spin-echo spectroscopy as well as x-ray photon correlation spectroscopy, in the context of planar lipid membrane models as an example. By the combination of the different methods, a large range in momentum and energy transfer is accessible.

We report a high energy-resolution neutron backscattering study to investigate slow motions on nanosecond time scales in highly oriented solid supported phospholipid bilayers of the model system DMPC -d54 (deuterated 1,2-dimyristoyl-sn-glycero-3-phoshatidylcholine), hydrated with heavy water. Wave vector resolved quasi-elastic neutron scattering (QENS) is used to determine relaxation times $\tau$, which can be associated with different molecular components, i.e., the lipid acyl chains and the interstitial water molecules in the different phases of the model membrane system. The inelastic data are complemented both by energy resolved and energy integrated in-situ diffraction. From a combined analysis of the inelastic data in the energy and time domain, the respective character of the relaxation, i.e., the exponent of the exponential decay is also determined. From this analysis we quantify two relaxation processes. We associate the fast relaxation with translational diffusion of lipid and water molecules while the slow process likely stems from collective dynamics.

Quasielastic neutron scattering experiments have been performed on proton-conducting hydrated Y-doped BaZrO3at temperatures between 473 K and 673 K. Quasielastic broadening is observed at all temperatures, but only at the higher ones the scattering exhibits the characteristics of the proton transport process. Attempts to interpret our data in the framework of the two-state model yield unconvincing results. A simpler approach using the isotropic Chudley-Elliott model yields reasonable values for the proton self-diffusivities but also unusually high values for the jump distance which are close to the mean distance between dopants.

The scattering image produced by coherent X-rays appears grainy and is denoted a speckle pattern. An analysis of the static and time-dependent properties of a speckle pattern generated by scattering of a partially coherent synchrotron beam from a liquid surface is given here. Unique surface sensitivity is achieved by applying the X-rays under a grazing angle of incidence. The observed contrast of the speckle pattern depends on the momentum transfer parallel to the surface, unlike the case of transmission small-angle X-ray scattering (SAXS), where essentially no q-dependence of the contrast has been observed. The appearance of the speckles and the contrast of the image can be understood qualitatively by use of geometrical arguments and by the fact that liquid surfaces are extremely flat.

The dynamics of propylene glycol (PG) and its oligomers 7-PG and poly-propylene glycol (PPG), with M(w) = 4000 (approximately 70 monomers), confined in a Na-vermiculite clay have been investigated by quasielastic neutron scattering. The liquids are confined to single molecular layers between clay platelets, giving a true two-dimensional liquid. Data from three different spectrometers of different resolutions were Fourier transformed to S(Q,t) and combined to give an extended dynamical time range of 0.3-2000 ps. An attempt was made to distinguish the diffusive motion from the methyl group rotation and a fast local motion of hydrogen in the polymer backbone. The results show that the average relaxation time tau(d) of this diffusive process is, as expected, larger than the relaxation time tau averaged over all dynamical processes observed in the experimental time window. More interesting, it is evident that the severe confinement has a relatively small effect on tau(d) at T = 300 K, this holds particularly for the longest oligomer, PPG. The most significant difference is that the chain-length dependence of tau(d) is weaker for the confined liquids, although the slowing down in bulk PG due to the formation of a three-dimensional network of OH-bonded end groups reduces this difference. The estimated average relaxation time tau at Q = 0.92 Angstroms(-1) for all the observed processes is in excellent agreement with the previously reported dielectric alpha relaxation time in the studied temperature range of 260-380 K. The average relaxation time tau (as well as the dielectric alpha relaxation time) is also almost unaffected by the confinement to a single molecular layer, suggesting that the interaction with the clay surfaces is weak and that the reduced dimensionality has only a weak influence on the time scale of all the dynamical processes observed in this study.

Quasi-elastic neutron scattering (QENS) has been used to study water adsorbed at different concentrations in BaX zeolite. It is found that, the lower the water content, the higher the temperature which is required to reach adsorption equilibrium. For a loading of 15 molecules per supercage, an evolution of the QENS intensity with time is observed at 440 K which suggests that the sample was not in equilibrium; for a loading of 10 molecules per supercage, this happens at 520 K. Even at the highest studied temperature, 520 K, the diffusion coefficient of water in the equilibrated samples is lower than 10–12 m2 s–1. This is much lower than in NaCaA zeolites, manifesting the very large interaction between water and the Ba cations. To cite this article: H. Jobie et al., C. R. Chimie 8 (2005).

We report a high energy-resolution neutron backscattering study to investigate slow motions on nanosecond time scales in highly oriented solid supported phospholipid bilayers of the model system DMPC -d54 (deuterated 1,2-dimyristoyl-sn-glycero-3-phoshatidylcholine), hydrated with heavy water. This technique allows to discriminate the onset of mobility at different length scales for the different molecular components, as e.g.\@ the lipid acyl-chains and the hydration water in between the membrane stacks, respectively, and provides a benchmark test regarding the feasibility of neutron backscattering investigations on these sample systems. We discuss freezing of the lipid acyl-chains, as observed by this technique, and observe a second freezing transition which we attribute to the hydration water.

We report on in situ x-ray reflectivity measurements of the surface roughness of supercooled glass forming polymers in a temperature range from 190 to 330 K. The experimentally determined rms roughness has been found to obey the capillary wave model of a single liquid/vapor interface over the entire temperature range. An expression for the surface roughness below the bulk glass transition (T(G) approximately equal to 200 K) is deduced from the viscoelastic theory of surface fluctuations; however, no indication of a frozen-in surface roughness has been observed in the experiment. Additionally, it is shown that precise values of the surface tension of highly viscous liquids in the supercooled state can be determined by x-ray reflectivity.

We measure the dispersion relation of capillary waves on a liquid surface by heterodyne x-ray photon correlation spectroscopy near the transition from propagating to overdamped dynamic behavior. A strong deviation of the propagation frequency from the small-damping result ${\ensuremath{\omega}}_{p}\ensuremath{\propto}{k}^{3/2}$ is observed long before the actual transition where $(\ensuremath{\partial}{\ensuremath{\omega}}_{p}/\ensuremath{\partial}k)l0$ and ${\ensuremath{\omega}}_{p}$ tends to zero. This behavior is successfully described by expressions derived within linear response theory.

A dedicated setup comprising an efficient cryogenic device for the in situ preparation of large surface areas of prototypical organic glass formers in a wide temperature range (170–340 K) is presented. This setup provides the necessary temperature and vibrational stability for surface x-ray and neutron scattering experiments, including the extremely sensitive technique of x-ray photon correlation spectroscopy (XPCS). XPCS is an emerging method which is made possible by the high coherent photon flux produced by third-generation synchrotrons. We demonstrate that microscopic motion at the surface can be studied in a direct way in the liquid and supercooled state using XPCS. In addition, we have used a charge-coupled-device detector to record two-dimensional images of static speckle patterns forming on surfaces in the glassy state.

We report measurements of propagating capillary waves on a liquid water surface at $T=5\text{ }\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ with x-ray photon correlation spectroscopy. The experiment has been performed under grazing incidence conditions with an incoming x-ray beam below the critical angle of total external reflection. In the $\mathbf{q}$ region investigated the measured intensity-intensity autocorrelation functions of the liquid water surface were found to be heterodyne signals, i.e., a combination of first- and second-order correlation functions ${g}_{1}(\ensuremath{\tau})$ and ${g}_{2}(\ensuremath{\tau})$.

Physical review / B 65(18), 184207 (2002). doi:10.1103/PhysRevB.65.184207, Published by Inst., Woodbury, NY

In the above article the name of one of the authors has been mistyped. The correct name of the author is D. Fernandez-Canoto.

Samples of nanoscale hematite, α-Fe2O3, with different surface geometries and properties have been studied with inelastic time-of-flight neutron scattering. The 15 nm diameter nanoparticles previously shown to have two collective magnetic excitation modes in separate triple-axis neutron scattering studies have been studied in further detail using the advantage of a large detector area, high resolution, and large energy transfer range of the IN5 TOF spectrometer. A mesoporous hematite sample has also been studied, showing similarities to that of the nanoparticle sample and bulk α-Fe2O3. Analysis of these modes provides temperature dependence of the magnetic anisotropy coefficient along the c-axis, κ1. This is shown to remain negative throughout the temperature range studied in both samples, providing an explanation for the previously observed suppression of the Morin transition in the mesoporous material. The values of this anisotropy coefficient are found to lie between those of bulk and nano-particulate samples, showing the hybrid nature of the mesoporous 3-dimensional structure.

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We report on a comprehensive study of the electronic structure of the layered semiconductor $1T\ensuremath{-}{\mathrm{HfS}}_{2}.$ The occupied and unoccupied band structure has been investigated by combined angle-resolved photoemission and inverse photoemission. The results are discussed in the context of a fully relativistic linear-muffin-tin-orbital calculation as well as an extended linear-augmented-plane-wave calculation showing a very good agreement between experiment and theory. From the measurements, we obtain an indirect band gap of 2.85 eV between $\ensuremath{\Gamma}$ and M/L. This value differs significantly from optical results $(\ensuremath{\approx}2\mathrm{eV}).$ In the normal direction we observe the direct band gap of 3.6 eV.

Physical review letters 83(17), 3470 - 3473 (1999). doi:10.1103/PhysRevLett.83.3470, The surfaces of liquid thin perfluorohexane, cyclohexane, decane, and ethanol films adsorbed on silicon wafers have been investigated by means of x-ray reflectivity, diffuse scattering, and grazing incidence diffraction. The measurements prove that the surface structure of the wetting films can be described by a universal height-height correlation function derived from a capillary wave model with the surface tension and particular cutoffs as parameters. The data favor a reduced capillary wave surface tension as predicted by exact theories, over an enhanced capillary wave surface tension, as suggested by simple mode-coupling models., Published by APS, College Park, Md.

A series of thin liquid hexane films adsorbed on a rough silicon wafer was studied with specular and off-specular X-ray scattering. Assuming an interfacial profile at the liquid–solid interface which does not depend on film thickness and modeling the density tail at the liquid–vapor interface by an error-function, we find an interfacial profile which explains the reflectivity data of all the measured 13 hexane films of thicknesses 25–350 A. The interfacial region near the substrate extends to 40 A from the solid–liquid interface and is in good agreement with calculated density profiles of Lennard–Jones fluids near a hard wall. For films thicker than 50 A the rms-roughness found for the liquid surface accounts well to predictions based on standard continuum capillary-wave theory. The surface roughness of thinner films is drastically reduced. Above 200 A a power law of the form qη−2r describes the diffusely scattered intensity.

The x-ray diffraction studies of the title complex were carried out at room temperature and 14 K for H/D (in hydrogen bridge) isotopomers. At 82 K a phase transition takes place leading to a doubling of unit cells and alternation of the hydrogen bond lengths linking tetramethylpyrazine (TMP) and chloranilic acid molecules. A marked H/D isotope effect on these lengths was found at room temperature. The elongation is much smaller at 14 K. The infrared isotopic ratio for O-H(D)...N bands equals to 1.33. The four tunnel splittings of methyl librational ground states of the protonated complex required by the structure are determined at a temperature T=4.2 K up to pressures P=4.7 kbars by high resolution neutron spectroscopy. The tunnel mode at 20.6 microeV at ambient pressure shifts smoothly to 12.2 microeV at P=3.4 kbars. This is attributed to an increase of the strength of the rotational potential proportional to r(-5.6). The three other tunnel peaks show no or weak shifts only. The increasing interaction with diminishing intermolecular distances is assumed to be compensated by a charge transfer between the constituents of deltae/e approximately 0.02 kbar(-1). The phase transition observed between 3.4 and 4.7 kbars leads to increased symmetry with only two more intense tunneling bands. In the isotopomer with deuterated hydrogen bonds and P=1 bar all tunnel intensities become equal in consistency with the low temperature crystal structure. The effect of charge transfer is confirmed by a weakening of rotational potentials for those methyl groups whose tunnel splittings were independent of pressure. Density functional theory calculations for the model TMP.(HF)2 complex and fully ionized molecule TMP+ point out that the intramolecular rotational potential of methyl groups is weaker in the charged species. They do not allow for the unequivocal conclusions about the role of the intermolecular charge transfer effect on the torsional frequencies.

The layered transition-metal oxide Nax CoO2 has been studied extensively both for its correlated electronic properties as well as for potential battery applications. It was discovered that high-temperature Na ion vacancy order and dynamics can be very useful to tailor low-temperature properties of members of this compound family. We have studied the Na-ion dynamics on the atomic length-scale in the Na0.7 CoO2 compound by neutron spectroscopy. The temperature dependence of both the elastic and the inelastic intensities show steps at TA ≈ 290 K and TB ≈ 400 K. At TA the step is shown to be connected to low energy phonons, while at TB the Na ion diffusion suddenly gets fast enough, and the characteristic signal of quasielastic scattering appears. The current results further elucidate the subtle changes in the Na ion dynamics that have been revealed in our previous neutron diffraction studies [1], intimately connecting structural transformations at TA and TB with the opening-up of 1D and 2D Na-ion diffusion paths. Finally, the estimated diffusion coefficient above TB was found to differ from the one measured by muon-spin relaxation (μ+SR) [2] by about four orders of magnitude. However it might be that the present QENS data rather describe a fast localized prozess than a long range translational diffusion. Within this model the corresponding time scale (ℏ/E) would be in the order of 50 ps., EPJ Web of Conferences, 83, ISSN:2100-014X, ISSN:2101-6275

Neurodegenerative diseases, such as Parkinson's and Alzheimer's, constitute a growingthreat with ever increasing prevalence. These diseases are characterized by the presence ofprotein deposits in the patient's brain that are called amyloids. Several proteins wereidentified in these deposits as being the molecular hallmark of the disorder, among whichwe can cite alpha-synuclein for Parkinson’s disease and tau for Alzheimers’s disease.Protein amyloid aggregation is central to neurodegenerative diseases and hence constitutesa target of choice for diagnostic and therapeutic attempts. Itis characterized by the formation of a structural cross-beta pattern, which is a stack ofbeta-sheets, usually forming long fibrils. Under specific conditions, larger aggregates can beobtained, such as micrometer-sized particles, including so-called particulates andspherulites. Several pieces of evidence suggest that the formation of such aggregates, and especially at early-stages, can be involved in protein toxicity. Yet, the reasons for theaggregation to occur are not well understood. In this work, we aimed at deciphering thefundamental principles underlying protein amyloid aggregation by studying the changesin protein ad hydration water dynamics, the understanding of which might help in the development ofwater-dynamics based diagnostic methods.We employed mainly incoherent neutron scattering (on SPHERES at the MLZ and IN16B at the ILL)and molecular dynamics simulations. Theformer provides ensemble averaged information on hydrogen motions in the system, and thelatter provides a fully atomistic picture from which dynamical and structural aspects canbe investigated.Studying alpha-synuclein, we could show that protein backbone and side-chain motions - that is,internal dynamics - is barely affected by aggregation. However, hydration water motions areincreased around amyloid fibrils. The increased dynamics originates from a fraction ofwater molecules being displaced from the protein hydrophobic core to the hydrophilictermini regions when fibrils are formed. Hence, it results in a higher water entropy in fibrils,where the central cross-beta pattern appears highly efficient in protecting itself frominteracting with the solvent.For gammaS-crystallin, comparison of the internal protein dynamics of the wild-type proteinwith a G18V mutant revealed that the mutant is less dynamic, whatever itsaggregation state. This observation, along with the comparison of protein dynamics withtheir relative hydropathy index, indicates that the internal dynamics depends strongly onthe amino acid composition, but not on the aggregation state. In addition, other factorscan affect protein dynamics, such as the presence of metal ions.The measurements carriedout on insulin, in the presence or absence of zinc show that the metal promotes proteinhydration at pH 1.8, where it interacts loosely with the protein. The zincaffects also aggregate-aggregate interaction, probably by electrostatic screening as theformation of spherulites is facilitated in the absence of the metal.Eventually, the possibility to unambiguously and simultaneously access internal dynamicsand center-of-mass diffusion was demonstrated by carrying out so-called fixed- window scanson the IN16B instrument at the ILL. This novel technique applied to lysozyme showed thatparticulate formation occurs in a one-step process, and the internal dynamics remainsconstant all along. This pilot experiment opens up the possibility to study fibrilformation of pathologically relevant proteins.Taken together, the aforementioned results demonstrate that we can now study the amyloidaggregation process with great detail, and there is a great opportunity to extend this workwithin a biological context, in order to link the biophysical properties of protein amyloidaggregation with its effects and toxicity in-vivo, Les maladies neurodégénératives, comme Parkinson ou Alzheimer, sont une menace croissante,avec une prévalence augmentant sans cesse. Ces maladies sont caractérisées par la présence de dépôts protéiques, appellés amyloïdes, dans le cerveau. Plusieurs protéines ont été identifiées dans ces dépôts comme étant des marqueurs de la maladie, dont l'alpha-synucléine pour Parkinson et tau pour Alzheimer. L'agrégation amyloïde est centrale dans les maladies neurodégénératives et constitue ainsi un cible privilégiée pour le diagnostic ou les essais cliniques.L'agrégation amyloïde est caractérisée par la formation d'un motif cross-β, qui consiste en un empilement de brins beta;, pouvant former ainsi de longues fibres. Dans certaines conditions,des particules de taille micrométrique peuvent être obtenus, tels que les 'particulates' ou les 'sphérulites'. Plusieurs études montrent que la formation des agrégats, en particulier au stade précoce,est impliquée dans la toxicité. En revanche, les raisons de l'agrégation des protéines ne sont pas bien comprises. Dans ce travail, nous avons cherché à comprendre les principes fondamentaux impliqués dans l'agrégation amyloïde, en étudiant les changements de dynamique du système protéine-solvent, ce qui de plus, pourrait aider le développement de nouvelles méthodes de diagnostic.Dans ce but, j'ai utilisé principalement la diffusion incohérente des neutrons et les simulations de dynamique moléculaire. La première fournit une dynamique moyennée sur l'ensemble des atomes d'hydrogène dans le système et la seconde fournit une vision atomique dans laquelle structure et dynamique peuvent être étudiées.En étudiant l'alpha-synucléine, j'ai montré que les mouvements des chaines latérales et principales - dynamique interne - sont inchangés par l'agrégation. Cependant, les mouvements de l'eau sont accélérés autour des fibres, ce qui provient d'une fraction de l'eau étant déplacée du coeur hydrophobe vers les régions terminales hydrophiles lors de la formation des fibres.Ainsi, l'entropie de l'eau est augmentée dans les fibres, ou le motif cross-beta; central semble être très efficace pour se protéger lui-même de l'intéraction avec le solvent. La comparaison de la gammaS-crystalline sauvage avec le mutant G18V montre que le mutant est moins dynamique, quel que soit l'état d'agrégation. Cette observation, et la comparaison de la dynamique interne avec l'hydrophobicité des protéines, montre que la dynamique interne dépend fortement de la composition en acides aminés et non pas de l'état d'agrégation. En outre,les ions métalliques peuvent aussi influencer la dynamique interne.Les mesures sur l'insuline, en présence ou absence de zinc montre que le métal aide à l'hydratation de la protéine, même à pH 1.8, où il interagit faiblement avec la protéine. Le zinc affecte aussi les interactions entre agrégats, probablement par écrantage électrostatique, étant donné que la formation de sphérulites est facilitée en son absence.Enfin, la possibilité de suivre en simultané, et sans ambiguïté, la dynamique interne et la diffusion du centre de masse a été démontrée en utilisant des scans à fenêtre d'énergie fixe sur l'instrument IN16B à l'ILL. Cette nouvelle méthode, appliquée au lysozyme, montre que la formation des 'particulates' se déroule en une étape, avec la dynamique interne restant constante tout au long du processus. Cette expérience pilote ouvre la voie à des études de fibrillation de protéines ayant un intérêt médical.Ensemble, ces résultats démontrent que l'on peut étudier le processus d'agrégation amyloïde avec beaucoup de détails, et il y a une grande opportunité d'étendre ce travail dans un contexte biologique afin de faire le lien entre les paramètres biophysiques de l'agrégation amyloïde et ses effets et sa toxicité in-vivo

Spider dragline silk is a remarkable material, a biopolymer with outstanding mechanical properties. Spider silk has been in the focus of intense research using a wide variety of experimental techniques and in addition theoretical modelling. However, its macroscopic properties are still not well linked to its microscopic structure and dynamics. Synchrotron radiation small- and wide-angle scattering experiments have in recent years particularly contributed to the development of microscopic structural models.In this thesis work, neutron scattering techniques have been used for the first time for the study of spider silk. The high scattering contribution of hydrogen and the scattering length difference of hydrogen and deuterium have allowed a fresh look at structural and dynamical properties of spider silks. Thus the results support a hierarchical, three-phase model of nanofibrils composed of crystalline and short-range order domains embedded in an amorphous matrix. Complementary synchrotron scattering experiments suggest that water absorbed by the amorphous matrix forms an amorphous ice at low temperatures. Wide-angle neutron scattering (WANS) experiments showed a meridional superlattice peak -not observed by X-ray (WAXS) experiments-, which is assigned to a smectic beta-sheet structure in the short-range order domains. The exchange of H2O against D2O in small-angle neutron scattering (SANS) experiments allowed changing the neutron scattering length density contrast in the nanofibrils and the contrast of the nanofibrils against the amorphous matrix. The molecular mobility was probed by inelastic and quasielastic neutron scattering techniques. A hierarchy of relaxation processes seems to describe hydrated silk, while native silk behaves like a glass at room temperature.; Le fil de traîne de l'araignée est un matériau remarquable, un biopolymère aux exceptionnelles propriétés mécaniques. La soie d'araignée a été au centre d'une intense recherche utilisant une large gamme de techniques expérimentales et de modélisations théoriques. Néanmoins, ses propriétés macroscopiques n'ont pas encore été correctement reliées à sa structure et sa dynamique microscopiques.Dans ce travail de thèse, les techniques de diffusion neutronique ont été pour la première fois utilisées pour l'étude de la soie d'araignée. La forte contribution de l'hydrogène en diffusion des neutrons ainsi que la différence des longueurs de diffusion de l'hydrogène et du deutérium ont permis de porter un regard nouveau sur les propriétés structurales et dynamiques des soies d'araignée. Ainsi les résultats appuient un modèle hiérarchique à trois phases de nanofibrilles composées de domaines cristallins et d'ordre à courte portée, contenues dans une matrice amorphe. Des expériences complémentaires de diffusion du rayonnement synchrotron suggèrent que l'eau absorbée par la matrice amorphe forme une glace amorphe à basses températures. Des expériences de diffraction de neutrons (abréviation anglaise : WANS) ont montré un pic méridional hors réseau -non observé par les expériences en rayons X (abréviation anglaise : WAXS)- attribué à une structure smectique de feuillets beta dans les domaines d'ordre à courte portée. L'échange de H2O contre D2O pour les expériences de diffusion de neutrons aux petits angles (abréviation anglaise : SANS) a permis d'observer la variation de contraste à l'intérieur des nanofibrilles et entre les nanofibrilles et la matrice. La mobilité moléculaire a été sondée par des techniques de diffusion inélastique et quasiélastique des neutrons. Il semble qu'une hiérarchie de phénomènes de relaxations décrive la soie hydratée, tandis que la soie native a un comportement vitreux à température ambiante.