Water-Dispersible FePt Nanoparticles Having ω-Mercapto-α-carboxylic Acid Ligands

2004 ◽  
Vol 853 ◽  
Author(s):  
Janis K. Mabry ◽  
Laura Beth Tackett ◽  
Hitesh Bargaria ◽  
Xiangcheng Sun ◽  
Earl T. Ada ◽  
...  
Keyword(s):  
Oleic Acid ◽  
Ammonium Hydroxide ◽  
Photoelectron Spectra ◽  
Fept Nanoparticles ◽  
X Ray ◽  
Water Dispersible ◽  
Ordered Arrays ◽  
Oleyl Amine ◽  
Counter Ions ◽  
Thiol Ligand

ABSTRACTFePt nanoparticles, ∼ 2nm in diameter, were prepared by the polyol reduction of platinum(II) acetylacetonate and iron(III) acetylacetonate in the presence of oleyl amine and oleic acid surfactants. The particles were dispersed in hexane and the dispersion added to a solution of 11-mercaptoundecanoic acid in cyclohexanone. As the 11-mercaptoundecanoic acid ligands replaced the oleic acid ligands, the particles precipitated. The particles could be dispersed in basic water, made basic either with sodium hydroxide or ammonium hydroxide. X-ray photoelectron spectra showed a peak near 164 eV, sulfur (2p) confirming the presence of the thiol ligand. Similarly, the oleic acid ligands were replaced with either 3-mercaptopropionic acid or 16-mercaptohexadecanoic acid to give FePt particles that could be dispersed in water. Dispersions made with FePt nanoparticles having 11-mercaptoundeacnoic acid ligands and ammonium counter ions were dried on TEM grids to give highly ordered films consisting of close-packed arrays of FePt nanoparticles. When the counter ion was sodium, the particles tended to aggregate, instead of forming ordered arrays.

RNA polymerase: Preparation and structural analysis of helical polymers

1984 ◽  
Vol 42 ◽  
pp. 152-153
Author(s):  
E. Loren Buhle ◽  
Pamela Rew ◽  
Ueli Aebi
Keyword(s):  
Structural Analysis ◽  
Rna Polymerase ◽  
Molecular Level ◽  
X Ray Diffraction ◽  
Helical Polymers ◽  
X Ray ◽  
E Coli ◽  
The Past ◽  
Ordered Arrays ◽  
Low Ionic Strength

While DNA-dependent RNA polymerase represents one of the key enzymes involved in transcription and ultimately in gene expression in procaryotic and eucaryotic cells, little progress has been made towards elucidation of its 3-D structure at the molecular level over the past few years. This is mainly because to date no 3-D crystals suitable for X-ray diffraction analysis have been obtained with this rather large (MW ~500 kd) multi-subunit (α2ββ'ζ). As an alternative, we have been trying to form ordered arrays of RNA polymerase from E. coli suitable for structural analysis in the electron microscope combined with image processing. Here we report about helical polymers induced from holoenzyme (α2ββ'ζ) at low ionic strength with 5-7 mM MnCl2 (see Fig. 1a). The presence of the ζ-subunit (MW 86 kd) is required to form these polymers, since the core enzyme (α2ββ') does fail to assemble into such structures under these conditions.

scholarly journals Modification of Wood with Monoethanolamino-borate by The Data of X-Ray Photoelectron Spectroscopy

2018 ◽  
Vol 196 ◽  
pp. 04005
Author(s):  
Irina Stepina ◽  
Irina Kotlyarova
Keyword(s):  
Particle Size ◽  
Photoelectron Spectroscopy ◽  
Model Compound ◽  
Hydrolytic Stability ◽  
Photoelectron Spectra ◽  
Wood Cellulose ◽  
Rapid Loss ◽  
X Ray ◽  
Wood Protection ◽  
Cellulose Materials

The difficulty of wood protection from biocorrosion and fire is due to the fact that modifiers in use are washed out from the surface of the substrate under the influence of environmental factors. This results in a rapid loss of the protective effect and other practically important wood characteristics caused by the modification. To solve this problem is the aim of our work. Here, monoethanolaminoborate is used as a modifier, where electron-donating nitrogen atom provides a coordination number equal to four to a boron atom, which determines the hydrolytic stability of the compounds formed. Alpha-cellulose ground mechanically to a particle size of 1 mm at most was used as a model compound for the modification. X-ray photoelectron spectra were recorded on the XSAM-800 spectrometer (Kratos, UK). Prolonged extraction of the modified samples preceded the registration of the photoelectron spectra to exclude the fixation of the modifier molecules unreacted with cellulose. As a result of the experiment, boron and nitrogen atoms were found in the modified substrate, which indicated the hydrolytic stability of the bonds formed between the modifier molecules and the substrate. Therefore monoethanolaminoborate can be considered as a non-extractable modifier for wood-cellulose materials.

scholarly journals Impact of high temperatures on aluminoceladonite studied by Mössbauer, Raman, X-ray diffraction and X-ray photoelectron spectroscopy

2021 ◽  
Author(s):  
Mariola Kądziołka-Gaweł ◽  
Maria Czaja ◽  
Mateusz Dulski ◽  
Tomasz Krzykawski ◽  
Magdalena Szubka
Keyword(s):  
Photoelectron Spectroscopy ◽  
Integral Intensity ◽  
Photoelectron Spectra ◽  
X Ray Diffraction ◽  
Structural Reorganization ◽  
Oh Groups ◽  
X Ray ◽  
Al Content ◽  
Integral Intensity Ratio ◽  
Higher Temperature

AbstractMössbauer, Raman, X-ray diffraction and X-ray photoelectron spectroscopies were used to examine the effects of temperature on the structure of two aluminoceladonite samples. The process of oxidation of Fe2+ to Fe3+ ions started at about 350 °C for the sample richer in Al and at 300 °C for the sample somewhat lower Al-content. Mössbauer results show that this process may be associated with dehydroxylation or even initiate it. The first stage of dehydroxylation takes place at a temperature > 350 °C when the adjacent OH groups are replaced with a single residual oxygen atom. Up to ~500 °C, Fe ions do not migrate from cis-octahedra to trans-octahedra sites, but the coordination number of polyhedra changes from six to five. This temperature can be treated as the second stage of dehydroxylation. The temperature dependence on the integral intensity ratio between bands centered at ~590 and 705 cm−1 (I590/I705) clearly reflects the temperature at which six-coordinated polyhedra are transformed into five-coordinated polyhedra. X-ray photoelectron spectra obtained in the region of the Si2p, Al2p, Fe2p, K2p and O1s core levels, highlighted a route to identify the position of Si, Al, K and Fe cations in a structure of layered silicates with temperature. All the measurements show that the sample with a higher aluminum content and a lower iron content in octahedral sites starts to undergo a structural reorganization at a relatively higher temperature than the less aluminum-rich sample does. This suggests that iron may perform an important role in the initiation of the dehydroxylation of aluminoceladonites.

X-RAY PHOTOELECTRON SPECTRA OF PHOSPHORUS YLIDES. PROBING THE PHOSPHORUS-CARBON YLIDE BOND

1974 ◽  
Vol 3 (5) ◽  
pp. 405-408 ◽  
Author(s):  
Manabu Seno ◽  
Shinji Tsuchiya ◽  
Teruzo Asahara
Keyword(s):  
Photoelectron Spectra ◽  
Phosphorus Ylides ◽  
X Ray

scholarly journals X-ray photoelectron spectra of iron-sulphur proteins

1975 ◽  
Vol 149 (2) ◽  
pp. 471-474 ◽  
Author(s):  
P T Andrews ◽  
C E Johnson ◽  
B Wallbank ◽  
R Cammack ◽  
D O Hall ◽  
...  
Keyword(s):  
Magnetic Susceptibility ◽  
Magnetic State ◽  
High Potential ◽  
Spin Coupling ◽  
Photoelectron Spectra ◽  
Clostridium Pasteurianum ◽  
Active Centre ◽  
Core Polarization ◽  
X Ray ◽  
Polarization Splitting

The X-ray photoelectron spectra of the 2p, 3s and 3p levels of iron in oxidized Clostridium pasteurianum ferredoxin indicate that the eight iron atoms in the molecule are indistinguishable. Their magnetic state is indicated both by core polarization splitting of the 3s electrons, and by ‘shake-up’ satellites on the 2p lines. Similar satellites are observed in the 2p lines of reduced Chromatium high-potential iron-sulphur proteins and oxidized spinach ferredoxin, indicating that there too the iron atoms are magnetic. The low observed magnetic susceptibility of these proteins is therefore due to spin-coupling between the iron atoms in the active centre.

X-ray emission and photoelectron spectra, and the location of fluorine atoms in strontium and calcium copper oxyfluorides

1996 ◽  
Vol 8 (26) ◽  
pp. 4847-4854 ◽  
Author(s):  
E Z Kurmaev ◽  
L V Elokhina ◽  
V V Fedorenko ◽  
S Bartkowski ◽  
M Neumann ◽  
...  
Keyword(s):  
Photoelectron Spectra ◽  
X Ray
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