Absence of molecular mobility on nano-second time scales in amorphous ice phases

Koza, Michael Marek; Geil, Burkhard; Schober, H.; Natali, Francesca

doi:10.1039/b414382e

Cited by 28 publications

(26 citation statements)

References 75 publications

(238 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Qualitative comparisons of DSC ͑differential scanning calo- 9. 51 It has been concluded based on high-resolution neutron backscattering measurements that LDA starts to crystallize into ice I c at T g = 135 K, i.e., at the originally proposed T g . ͑a͒ OH stretching region; ͑b͒ low frequency lattice vibration region.…”

Section: Discussionmentioning

confidence: 99%

In situ Raman spectroscopy of low-temperature/high-pressure transformations of H2O

Yoshimura

Stewart

Mao

et al. 2007

The Journal of Chemical Physics

View full text Add to dashboard Cite

In situ Raman spectra of transformations of H2O as functions of pressure and temperature have been measured starting from high-density amorphous ice (HDA). Changes above Tx, the crystallization temperature of HDA, were observed. The spectra provide evidence for an abrupt, first-order-like, structural change that appears to be distinct from those associated with the transformation between low-density amorphous ice (LDA) and HDA. In separate experiments, in situ Raman spectra of ice XII transformed from HDA have been measured at various P-T regions, in order to improve the understanding of the stability limits of ice XII. The spectra of ices VI and XII differ in shape, but the vibrational frequencies are very close in the same P-T regimes. A metastable phase of ice found to form within the stability field of ice VI appears to be distinct from ice XII.

show abstract

Section: Discussionmentioning

confidence: 99%

In situ Raman spectroscopy of low-temperature/high-pressure transformations of H2O

Yoshimura

Stewart

Mao

et al. 2007

The Journal of Chemical Physics

View full text Add to dashboard Cite

show abstract

“…2 and SI Table 1). Bulk crystalline ice measured on the same neutron spectrometer has been shown to behave as a harmonic solid up to its melting point without any transition at 200 K (46). Therefore, we ascribe the inflection at 200 K exclusively to a transition in the dynamics of water in the first hydration layer in contact with the membrane surface.…”

Section: Hydration Water and Membrane Msds As A Function Of Temperaturementioning

confidence: 99%

Coupling of protein and hydration-water dynamics in biological membranes

Wood

Plazanet

Gabel

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

155

174

View full text Add to dashboard Cite

The dynamical coupling between proteins and their hydration water is important for the understanding of macromolecular function in a cellular context. In the case of membrane proteins, the environment is heterogeneous, composed of lipids and hydration water, and the dynamical coupling might be more complex than in the case of the extensively studied soluble proteins. Here, we examine the dynamical coupling between a biological membrane, the purple membrane (PM), and its hydration water by a combination of elastic incoherent neutron scattering, specific deuteration, and molecular dynamics simulations. Examining completely deuterated PM, hydrated in H2O, allowed the direct experimental exploration of water dynamics. The study of natural abundance PM in D2O focused on membrane dynamics. The temperature-dependence of atomic mean-square displacements shows inflections at 120 K and 260 K for the membrane and at 200 K and 260 K for the hydration water. Because transition temperatures are different for PM and hydration water, we conclude that ps-ns hydration water dynamics are not directly coupled to membrane motions on the same time scale at temperatures <260 K. Molecular-dynamics simulations of hydrated PM in the temperature range from 100 to 296 K revealed an onset of hydration-water translational diffusion at Ϸ200 K, but no transition in the PM at the same temperature. Our results suggest that, in contrast to soluble proteins, the dynamics of the membrane protein is not controlled by that of hydration water at temperatures <260 K. Lipid dynamics may have a stronger impact on membrane protein dynamics than hydration water. molecular dynamics simulations ͉ neutron spectroscopy ͉ dynamical transition ͉ purple membrane ͉ bacteriorhodopsin P roteins are animated by a multitude of motions occurring on various length and time scales. In a current model, a protein is not characterized by a single three dimensional structure but, rather, by a large number of conformations, so-called conformational substates, that interconvert via molecular motions (1). Natively unfolded proteins reflect this conformational heterogeneity to an extreme degree. The developing concept of a free-energy landscape has put some order into the complex world of protein motions (1). The energy landscape is a highdimensional space, in which each conformational substate is defined by the coordinates of all atoms in the protein. The energy landscape is organized in a hierarchy of levels; the top level containing only a few substates that interconvert by relatively slow large-scale movements (2). Each substate at this level contains, itself, a larger number of substates, separated by smaller barriers that are sampled by more rapid motions. At the third level, the number of substates becomes very large and the barriers very small, and motions at this level have been proposed to take place on the ps-ns time scale (2). Which of the motions on different levels are crucial for biological function and whether and how they are correlated with each other are chall...

show abstract

“…The PLS persists in the explored Q range and timescales of the experiments not only beyond their recrystallization to ice I c (Koza, Geil, Schober & Natali, 2005; SANS data not shown here) but also upon annealing HDA into the very high density modification (Koza et al, 2006). We tried to reduce the PLS intensity, e.g.…”

Section: Appendix a Porod-limit Scatteringmentioning

confidence: 99%

“…In analogy to the features of the WAD signal described by Koza, Geil, Schober & Natali (2005), we can find for any IðQ; t; T ¼ 103 KÞ a matching signal observed at a different T after a well defined but different evolution time t. As a consequence, it is not only the mere presence of a SANS signal that is characteristic of the intermediate structures, but it is in particular its intensity and the details of its profile that discern and, basically, define distinct transition stages.…”

Section: Static Properties Of Hda and Ldamentioning

confidence: 99%

See 1 more Smart Citation

On the heterogeneous character of water's amorphous polymorphism

2007

View full text Add to dashboard Cite

In this paper we report in situ small-angle neutron scattering results on the highdensity amorphous (HDA) and low-density amorphous (LDA) ice structures and on intermediate structures as found during the temperature-induced transformation of HDA into LDA. We show that the small-angle signal is characterized by two Q regimes featuring different properties [Q is the modulus of the scattering vector defined as Q ¼ ð4 = i Þ sinð Þ with being half the scattering angle and i the incident neutron wavelength]. The very low Q regime (< $ 5 Â 10 À2 Å À1 ) is dominated by a Porod-limit scattering. Its intensity reduces during the course of the HDA-to-LDA transformation following kinetics reminiscent of those observed in wide-angle diffraction experiments. The small-angle neutron scattering form factor in the intermediate regime of 5 Â 10 À2 < Q < 0:5 Å À1 for HDA and LDA features a rather flat plateau. However, the HDA signal shows an ascending intensity towards smaller Q marking this amorphous structure as heterogeneous. When following the HDAto-LDA transition, the form factor shows a pronounced transient excess in intensity marking all intermediate structures as strongly heterogeneous on a length scale of some nanometres.

show abstract

Absence of molecular mobility on nano-second time scales in amorphous ice phases

Cited by 28 publications

References 75 publications

In situ Raman spectroscopy of low-temperature/high-pressure transformations of H2O

In situ Raman spectroscopy of low-temperature/high-pressure transformations of H2O

Coupling of protein and hydration-water dynamics in biological membranes

On the heterogeneous character of water's amorphous polymorphism

Contact Info

Product

Resources

About