scholarly journals Insights into the mechanism of X-ray-induced disulfide-bond cleavage in lysozyme crystals based on EPR, optical absorption and X-ray diffraction studies

2013 ◽  
Vol 69 (12) ◽  
pp. 2381-2394 ◽  
Author(s):  
Kristin A. Sutton ◽  
Paul J. Black ◽  
Kermit R. Mercer ◽  
Elspeth F. Garman ◽  
Robin L. Owen ◽  
...  
Keyword(s):  
Radiation Damage ◽  
Disulfide Bond ◽  
Disulfide Bonds ◽  
Bond Cleavage ◽  
Absorbed Dose ◽  
Product Formation ◽  
Visible Absorption ◽  
Structural Investigations ◽  
X Ray ◽  
Uv Visible

Electron paramagnetic resonance (EPR) and online UV–visible absorption microspectrophotometry with X-ray crystallography have been used in a complementary manner to follow X-ray-induced disulfide-bond cleavage. Online UV–visible spectroscopy showed that upon X-irradiation, disulfide radicalization appeared to saturate at an absorbed dose of approximately 0.5–0.8 MGy, in contrast to the saturating dose of ∼0.2 MGy observed using EPR at much lower dose rates. The observations suggest that a multi-track model involving product formation owing to the interaction of two separate tracks is a valid model for radiation damage in protein crystals. The saturation levels are remarkably consistent given the widely different experimental parameters and the range of total absorbed doses studied. The results indicate that even at the lowest doses used for structural investigations disulfide bonds are already radicalized. Multi-track considerations offer the first step in a comprehensive model of radiation damage that could potentially lead to a combined computational and experimental approach to identifying when damage is likely to be present, to quantitate it and to provide the ability to recover the native unperturbed structure.

scholarly journals The susceptibility of disulfide bonds towards radiation damage may be explained by S...O interactions

IUCrJ ◽  
2020 ◽  
Vol 7 (5) ◽  
pp. 825-834
Author(s):  
Rajasri Bhattacharyya ◽  
Jesmita Dhar ◽  
Shubhra Ghosh Dastidar ◽  
Pinak Chakrabarti ◽  
Manfred S. Weiss
Keyword(s):  
Electron Transfer ◽  
Disulfide Bond ◽  
Disulfide Bonds ◽  
Metal Ion ◽  
Structural Information ◽  
Close Contact ◽  
Bond Cleavage ◽  
Protein Structures ◽  
Protein Crystal ◽  
X Ray

Radiation-induced damage to protein crystals during X-ray diffraction data collection is a major impediment to obtaining accurate structural information on macromolecules. Some of the specific impairments that are inflicted upon highly brilliant X-ray irradiation are metal-ion reduction, disulfide-bond cleavage and a loss of the integrity of the carboxyl groups of acidic residues. With respect to disulfide-bond reduction, previous results have indicated that not all disulfide bridges are equally susceptible to damage. A careful analysis of the chemical environment of disulfide bonds in the structures of elastase, lysozyme, acetylcholinesterase and other proteins suggests that S—S bonds which engage in a close contact with a carbonyl O atom along the extension of the S—S bond vector are more susceptible to reduction than the others. Such an arrangement predisposes electron transfer to occur from the O atom to the disulfide bond, leading to its reduction. The interaction between a nucleophile and an electrophile, akin to hydrogen bonding, stabilizes protein structures, but it also provides a pathway of electron transfer to the S—S bond, leading to its reduction during exposure of the protein crystal to an intense X-ray beam. An otherwise stabilizing interaction can thus be the cause of destabilization under the condition of radiation exposure.

Synthesis and Characterizations of Nanocubes, Monodispersed Nanocrystals and Nanospheres of Au

2007 ◽  
Vol 353-358 ◽  
pp. 2163-2166
Author(s):  
Ming Yang ◽  
Guo Qing Zhou ◽  
Jiang Guo Zhao ◽  
Zhan Jun Li
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Powder Diffraction ◽  
Visible Absorption ◽  
X Ray ◽  
Transmission Electron ◽  
Uv Visible ◽  
Scherrer Formula ◽  
Visible Absorption Spectroscopy

Nanocubes, monodispersed nanocrystals and nanospheres of Au have been prepared by a simple reaction between HAuCl4·4H2O, NaOH and NH2OH·HCl in the presence of gelatin. The role of gelatin and the affection of pH in producing the nanoparticles of Au were discussed. The products were characterized by X-ray powder diffraction, transmission electron microscopy, and UV-visible absorption spectroscopy. The sizes of the monodispersed nanocrystals of Au were estimated by Debye-Scherrer formula according to XRD spectrum.

Photoactive amphiphiles for the assembly of supramolecular architectures

2015 ◽  
Vol 185 ◽  
pp. 471-479 ◽  
Author(s):  
B. P. Jarman ◽  
F. Cucinotta
Keyword(s):  
Visible Spectrum ◽  
Solid Materials ◽  
Visible Absorption ◽  
Optical Components ◽  
Absorption And Emission ◽  
X Ray ◽  
Supramolecular Architectures ◽  
Uv Visible ◽  
Absorption And Emission Spectroscopy ◽  
Molecular Organisation

The presented study reports the use of photoactive templating structures for the design of porous frameworks with built-in optical functionalities. The materials have been synthesised and characterised using powder X-ray diffractometry, UV-visible absorption and emission spectroscopy. The latter shows that, by varying the relative amount of an amphiphilic chromophore in the micellar templates, it is possible to tune the light absorption and emission properties over the visible spectrum, by means of controlling the molecular organisation and the excitonic coupling of aggregated species. This enables versatile solid materials that can be used as optical components for light-harvesting and converting systems to be obtained .

Structural and optical properties of Ba(Co1−xZnx)SiO4 (x = 0.2, 0.4, 0.6, 0.8)

2019 ◽  
Vol 34 (3) ◽  
pp. 242-250 ◽  
Author(s):  
J. Anike ◽  
R. Derbeshi ◽  
W. Wong-Ng ◽  
W. Liu ◽  
D. Windover ◽  
...  
Keyword(s):  
Lattice Parameter ◽  
X Ray Diffraction ◽  
Powder Diffraction File ◽  
Visible Absorption ◽  
X Ray ◽  
Lattice Volume ◽  
Uv Visible ◽  
Diffraction Patterns ◽  
Pattern Determination ◽  
Bright Blue

Structural characterization and X-ray reference powder pattern determination have been conducted for the Co- and Zn-containing tridymite derivatives Ba(Co1−xZnx)SiO4 (x = 0.2, 0.4, 0.6, 0.8). The bright blue series of Ba(Co1−xZnx)SiO4 crystallized in the hexagonal P63 space group (No. 173), with Z = 6. While the lattice parameter “a” decreases from 9.126 (2) Å to 9.10374(6) Å from x = 0.2 to 0.8, the lattice parameter “c” increases from 8.69477(12) Å to 8.72200(10) Å, respectively. Apparently, despite the similarity of ionic sizes of Zn2+ and Co2+, these opposing trends are due to the framework tetrahedral tilting of (ZnCo)O4. The lattice volume, V, remains comparable between 626.27 Å3 and 626.017 (7) Å3 from x = 0 to x = 0.8. UV-visible absorption spectrum measurements indicate the band gap of these two materials to be ≈3.3 and ≈3.5 eV, respectively, therefore potential UV photocatalytic materials. Reference powder X-ray diffraction patterns of these compounds have been submitted to be included in the Powder Diffraction File (PDF).

scholarly journals Preparation of Fe-DopedTiO2Nanotubes and Their Photocatalytic Activities under Visible Light

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Honghui Teng ◽  
Shukun Xu ◽  
Dandan Sun ◽  
Ying Zhang
Keyword(s):  
Visible Light ◽  
Visible Region ◽  
Molar Ratio ◽  
X Ray Diffraction ◽  
Visible Absorption ◽  
X Ray ◽  
Transmission Electron ◽  
Photocatalytic Activities ◽  
Ultrasonic Assisted ◽  
Uv Visible

Fe-doped TiO2nanotubes (Fe-TNTs) have been prepared by ultrasonic-assisted hydrothermal method. The structure and composition of the as-prepared TiO2nanotubes were characterized by transmission electron microscopy, X-ray diffraction, and UV-Visible absorption spectroscopy. Their photocatalytic activities were evaluated by the degradation of MO under visible light. The UV-visible absorption spectra of the Fe-TNT showed a red shift and an enhancement of the absorption in the visible region compared to the pure TNT. The Fe-TNTs were provided with good photocatalytic activities and photostability and under visible light irradiation, and the optimum molar ratio of Ti : Fe was found to be 100 : 1 in our experiments.

Design and Optical Properties of Rare Earth-Based Mixed-Anions (O, S, F) Compounds

2002 ◽  
Vol 755 ◽  
Author(s):  
Damien Pauwels ◽  
Alain Demourgues ◽  
Alain Tressaud
Keyword(s):  
Optical Properties ◽  
Rare Earth ◽  
Solid State ◽  
Visible Absorption ◽  
X Ray ◽  
Solid State Route ◽  
Earth Environment ◽  
Fluorite Type ◽  
Uv Visible ◽  
Single Crystal Analysis

ABSTRACTRare earth-based mixed-anions (O, S, F) compounds have been prepared by solid state route. The structures have been determined on the basis of powder diffraction (X-ray/neutrons) refinement and/or single crystal analysis. They have been described as a stacking of [Sx] 2x- layers and fluorite type blocks. The evaluation of the rare earth environment (bondlength, number of neighbors) can be directly related to the bandgap and to the UV-visible absorption in the La-based compounds.

Mixed-Solvothermal Preparation of Mace-Like CdS Nanocrystals

2012 ◽  
Vol 502 ◽  
pp. 164-168
Author(s):  
Ling Xu ◽  
Han Mei Hu ◽  
Hai Yan Xu
Keyword(s):  
Electron Microscopy ◽  
Large Scale ◽  
Volume Ratio ◽  
X Ray Diffraction ◽  
Visible Absorption ◽  
X Ray ◽  
Transmission Electron ◽  
Cds Nanostructures ◽  
Uv Visible ◽  
Solvothermal Preparation

Novel mace-like (wolf-teeth clubs) CdS nanostructures were successfully prepared on a large scale using CdCl2•2.5H2O and NH2CSNH2 as starting materials through a convenient mixed-solvothermal route. The as-synthesized products were characterized by X-ray diffraction (XRD), energy dispersive X-ray spectrometry (EDX), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and UV-visible absorption spectroscopy. The experimental results reveal that the morphology of CdS products was greatly affected by the volume ratio of anhydrous ethanol and distilled water. The possible mechanism for the formation of mace-like CdS nanostructures is simply discussed.

scholarly journals Quantitative study of contrast enhancement in soft X-ray micrographs of insect eyes by tissue selective mass loss

2014 ◽  
Vol 21 (5) ◽  
pp. 1153-1159 ◽  
Author(s):  
Andreas Späth ◽  
Benjamin Watts ◽  
Lutz Thilo Wasserthal ◽  
Rainer H. Fink
Keyword(s):  
Mass Loss ◽  
Contrast Enhancement ◽  
Radiation Damage ◽  
Soft Matter ◽  
Absorbed Dose ◽  
Radiochemical Analysis ◽  
X Ray ◽  
Quantitative Studies ◽  
Radiation Induced ◽  
Energy Dependent

Quantitative studies of soft X-ray induced radiation damage in zone-plate-based X-ray microspectroscopy have so far concentrated on investigations of homogeneous specimens. However, more complex materials can show unexpected radiation-induced behaviour. Here a quantitative radiochemical analysis of biological tissue fromXantophan morganii praedictaeyes is presented. Contrast enhancement due to tissue selective mass loss leading to a significant improvement of imaging quality is reported. Since conventional quantitative analysis of the absorbed dose cannot conclusively explain the experimental observations on photon-energy-dependent radiation damage, a significant contribution of photo- and secondary electrons to soft matter damage for photon energies above the investigated absorption edge is proposed.

scholarly journals A New Non-Centrosymmetricorganotin (IV) Hybrid Compound C5H14N2 [SnCl6] 2H2O: Crystal Structure And Optical Study Characterization

2021 ◽  
Author(s):  
Nejeh Hannachi ◽  
Thierry ROISNEL ◽  
Faouzi HLEL
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Optical Band Gap ◽  
X Ray Diffraction ◽  
Absorption Bands ◽  
Hybrid Compound ◽  
Visible Absorption ◽  
X Ray ◽  
Uv Visible ◽  
Absorption Measurements

Abstract A new non-centrosymmetricorganotin (IV) hybrid compoundC5H14N2 [SnCl6] 2H2O was determined by single crystal X-ray diffraction at 150(2) K. Its crystal structure was solved by single crystal X-ray diffraction reveling that compound crystallizes in the orthorhombic system with Pbca space group with the following lattice parameters: a = 12.1486 (15) Å, b= 15.4571 (17) Å, c = 16.7610 (18) Å with Z = 8. The bonding between inorganic and organic entities in the compounds is realized by hydrogen bonding O−H…O ,O−H…Cl , NH • • • Cl, N-H…Cl and O−H…Cl. Finally,UV-visible absorption measurements exhibit two absorption bands (226 nm and 262 nm).The optical band gap (Eg) is deduced to be 3.46 Ev.

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