scholarly journals Diffusive dynamics during the high-to-low density transition in amorphous ice

2017 ◽  
Vol 114 (31) ◽  
pp. 8193-8198 ◽  
Author(s):  
Fivos Perakis ◽  
Katrin Amann-Winkel ◽  
Felix Lehmkühler ◽  
Michael Sprung ◽  
Daniel Mariedahl ◽  
...  
Keyword(s):  
Slow Component ◽  
Correlation Spectroscopy ◽  
Low Density ◽  
X Ray ◽  
Amorphous Ice ◽  
X Ray Scattering ◽  
Liquid Transition ◽  
Diffusive Dynamics ◽  
Momentum Transfer Dependence ◽  
Ray Scattering

Water exists in high- and low-density amorphous ice forms (HDA and LDA), which could correspond to the glassy states of high- (HDL) and low-density liquid (LDL) in the metastable part of the phase diagram. However, the nature of both the glass transition and the high-to-low-density transition are debated and new experimental evidence is needed. Here we combine wide-angle X-ray scattering (WAXS) with X-ray photon-correlation spectroscopy (XPCS) in the small-angle X-ray scattering (SAXS) geometry to probe both the structural and dynamical properties during the high-to-low-density transition in amorphous ice at 1 bar. By analyzing the structure factor and the radial distribution function, the coexistence of two structurally distinct domains is observed at T = 125 K. XPCS probes the dynamics in momentum space, which in the SAXS geometry reflects structural relaxation on the nanometer length scale. The dynamics of HDA are characterized by a slow component with a large time constant, arising from viscoelastic relaxation and stress release from nanometer-sized heterogeneities. Above 110 K a faster, strongly temperature-dependent component appears, with momentum transfer dependence pointing toward nanoscale diffusion. This dynamical component slows down after transition into the low-density form at 130 K, but remains diffusive. The diffusive character of both the high- and low-density forms is discussed among different interpretations and the results are most consistent with the hypothesis of a liquid–liquid transition in the ultraviscous regime.

Correlation of Small-Angle X-Ray Scattering and Solar Cell Performance of a-SiGe:H Alloys

1993 ◽  
Vol 297 ◽  
Author(s):  
S.J. Jones ◽  
Y. Chen ◽  
D.L. Williamson ◽  
X. Xu ◽  
J. Yang ◽  
...  
Keyword(s):  
Solar Cell ◽  
Small Angle ◽  
Film Surface ◽  
Nanometer Scale ◽  
Low Density ◽  
Solar Cell Performance ◽  
X Ray ◽  
X Ray Scattering ◽  
Cell Structures ◽  
Ray Scattering

Small-angle x-ray scattering (SAXS) measurements were made on a-SiGe:H alloys to study microstructure on the nanometer scale as a function of Ge content, and the results were compared with representative single-junction solar cell properties. Samples consisting of only the i-layer were used for SAXS. Above a Ge content of 20 %, a significant increase in SAXS was seen. From measurements made with the samples tilted relative to the incident x-ray beam, the increase in scattering is attributed to the appearance of elongated low density regions in the film, modeled as ellipsoidal microvoids, which are preferentially oriented perpendicular to the film surface and may be related to columnar-like microstructure. Flotation density measurements support the presence of low density regions. Initial and light-degraded measurements on corresponding solar cell structures do not show a correlation between SAXS and initial cell properties; there is, however, some evidence that the light-induced degradation is higher for cells with larger amounts of SAXS-detected microstructure and this needs further investigation.

scholarly journals Distinguishing Between Monomeric scFv and Diabody in Solution Using Light and Small Angle X-ray Scattering

Antibodies ◽  
2019 ◽  
Vol 8 (4) ◽  
pp. 48
Author(s):  
Frank Lüdel ◽  
Sandra Bufe ◽  
Willem M. Bleymüller ◽  
Hugo de de Jonge ◽  
Luisa Iamele ◽  
...  
Keyword(s):  
Small Angle ◽  
Antibody Fragment ◽  
Correlation Spectroscopy ◽  
Size Exclusion ◽  
Single Chain ◽  
X Ray ◽  
X Ray Scattering ◽  
Single Chain Fv ◽  
Exclusion Chromatography ◽  
Ray Scattering

Depending on the linker length between the V H and the V L domain, single-chain Fv (scFv) antibody fragments form monomers, dimers (diabodies) or higher oligomers. We aimed at generating a diabody of the anti-MET antibody 3H3 to use it as crystallization chaperone to promote crystallization of the MET ectodomain through the introduction of a pre-formed twofold axis of symmetry. Size exclusion chromatography, however, suggested the protein to be monomeric. Hence, we used scattering techniques applied to solutions to further investigate its oligomerization state. The small angle X-ray scattering (SAXS) curve measured for our protein nicely fits to the scattering curve calculated from the known crystal structure of a diabody. In addition, concentration-dependent photon correlation spectroscopy (PCS) measurements revealed a hydrodynamic radius of 3.4 nm at infinite dilution and a negative interaction parameter k D , indicating attractive interactions that are beneficial for crystallization. Both SAXS and PCS measurements clearly suggest our antibody fragment to be a diabody in solution. Chemical cross-linking with glutaraldehyde and cell motility assays confirmed this conclusion.

Small- and wide-angle X-ray scattering characterization of 1-hexene linear low-density polyethylene

1995 ◽  
Vol 196 (8) ◽  
pp. 2537-2544 ◽  
Author(s):  
Antonio Marigo ◽  
Gianmatteo Cingano ◽  
Carla Marega ◽  
Roberto Zannetti ◽  
Giuseppe Ferrara ◽  
...  
Keyword(s):  
Low Density Polyethylene ◽  
Low Density ◽  
Wide Angle ◽  
Linear Low Density Polyethylene ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

Coherent X-ray scattering beamline at port 9C of Pohang Light Source II

2013 ◽  
Vol 21 (1) ◽  
pp. 264-267 ◽  
Author(s):  
Chung-Jong Yu ◽  
Hae Cheol Lee ◽  
Chan Kim ◽  
Wonsuk Cha ◽  
Jerome Carnis ◽  
...  
Keyword(s):  
Light Source ◽  
Correlation Spectroscopy ◽  
X Rays ◽  
Photon Correlation ◽  
X Ray ◽  
Coherent Diffraction Imaging ◽  
X Ray Scattering ◽  
Pohang Light Source ◽  
Diffraction Imaging ◽  
Ray Scattering

The coherent X-ray scattering beamline at the 9C port of the upgraded Pohang Light Source (PLS-II) at Pohang Accelerator Laboratory in Korea is introduced. This beamline provides X-rays of 5–20 keV, and targets coherent X-ray experiments such as coherent diffraction imaging and X-ray photon correlation spectroscopy. The main parameters of the beamline are summarized, and some preliminary experimental results are described.

scholarly journals Time-course studies by synchrotron X-ray solution scattering of the structure of human low-density lipoprotein during Cu2+-induced oxidation in relation to changes in lipid composition

1996 ◽  
Vol 319 (1) ◽  
pp. 217-227 ◽  
Author(s):  
David F MEYER ◽  
Adam S NEALIS ◽  
Colin H. MacPHEE ◽  
Pieter H. E. GROOT ◽  
Keith E. SUCKLING ◽  
...  
Keyword(s):  
Oxidized Ldl ◽  
Ldl Oxidation ◽  
Radius Of Gyration ◽  
Lipid Hydroperoxides ◽  
Low Density ◽  
X Rays ◽  
X Ray ◽  
Lipid Core ◽  
X Ray Scattering ◽  
Ray Scattering

Low-density lipoproteins (LDLs) in plasma are constructed from a single molecule of apolipoprotein B-100 (apoB) (Mr 512000) in association with lipid [approximate Mr (2–3)×106]. LDL oxidation is an important process in the development of atherosclerosis, and can be imitated by the addition of Cu2+ ions. Synchrotron X-ray scattering of LDL yields curves without radiation damage effects at concentrations close to physiological. The radius of gyration RG for preparations of LDL from different donors ranged between 12.1 and 16.0 nm, with a mean of 13.9 nm. At 4 °C, the distance distribution curve P(r) indicated a maximum dimension of 25–27 nm for LDL, a peak at 19.5 nm which corresponds to a surface shell of protein and phospholipid head groups in LDL, and submaxima between 1.7 and 13.5 nm, which correspond to an ordered lipid core in LDL. LDL from different donors exhibited distinct P(r) curves. For oxidation studies of LDL by X-rays, data are best obtained at 4 °C at a concentration of ⩾ 2 mg of LDL protein/ml together with controls based on non-oxidized LDL. LDL oxidation (2 mg of apoB/ml) was studied at 37 °C in the presence of 6.4, 25.6 and 51.2 µmol of Cu2+/g of apoB. Large changes in P(r) were reproducibly observed in the inter-particle distance range between 13 and 16 nm shortly after initiation of oxidation. This corresponds to the phospholipid hydrocarbon in LDL, which has either increased in electron density during oxidation or become increasingly disordered. After 25 h, the structural changes subsequently spread to regions of the P(r) curves assigned to surface apoB and the central core of cholesteryl esters and triacylglycerols. Lipid analyses were carried out under the same solution conditions. The α-tocopherol and β-carotene antioxidant contents of LDL were consumed within 1–2 h. Analyses of the formation of thiobarbituric acid-reactive substances and lipid hydroperoxides indicated that arachidonic acid was preferentially oxidized before the maximal formation of lipid hydroperoxides at 8–12 h after initiation of oxidation. High-performance TLC showed that phosphatidylcholine was continuously converted into lysophosphatidylcholine during oxidation, which is consistent with the early changes in the X-ray P(r) curves. The neutral core lipids became modified only after 12–15 h of oxidation. The combination of X-ray scattering structural analyses with biochemical analyses shows that the oxidation of LDL first affects the outer shell of surface phospholipid, then it spreads towards damage of apoB and the internal neutral lipid core of LDL.

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