The stability of the lattice structure in low salt T-state haemoglobin crystals

1993 ◽  
Vol 442 (1914) ◽  
pp. 193-205 ◽  
Keyword(s):  
Lattice Structure ◽  
Special Property ◽  
Structural Basis ◽  
Salt Bridges ◽  
X Ray Diffraction ◽  
Salt Solutions ◽  
X Ray ◽  
Low Salt ◽  
The Stability ◽  
T State

The reconstruction of the electron density of molecules in crystals from X-ray diffraction measurements depends on the exactness of the packing of the molecules in the unit cell and the crystal lattice. Crystals of T-state haemoglobin, the low affinity form of the molecule, grow from high salt solutions or from low salt solutions in the presence of polyethylene glycol. The low salt lattice has the special property that it allows the haemoglobin molecule to bind oxygen and other ligands without the crystal breaking up. The stability of the low salt T-state crystals appears to arise from a small number of well-defined salt bridges and hydrogen bonds that are concentrated in specific lattice directions. These together form a framework within which the molecule can make adjustments which are sufficient to accommodate ligand binding but in which the larger quaternary movements normally associated with oxygenation are prevented. In these crystals therefore interactions with ligands can be studied directly by X-ray diffraction and the structural basis of the T-state’s low affinity for oxygen can be analysed.

Study of the Phases of Mg-Zn-La Magnesium Alloys at 150°C

2013 ◽  
Vol 750-752 ◽  
pp. 679-682 ◽  
Author(s):  
Ming Li Huang ◽  
Li Na Dong ◽  
Ying Ling Wang ◽  
Li Wei Quan
Keyword(s):  
Phase Equilibrium ◽  
Lattice Structure ◽  
Stable Phase ◽  
X Ray Diffraction ◽  
Binary Solid Solution ◽  
Two Phase ◽  
X Ray ◽  
The Difference ◽  
The Stability ◽  
T Phase

Alloys with different compositions in Mg-rich corner of Mg-Zn-La system at 150°C were prepared, and the phase equilibrium in Mg-Zn-La alloys were determined by scanning electron microscopy (SEM), electron probe microanalysis based on energy dispersive X-ray spectroscopy (EPMA-EDS) and X-ray diffraction (XRD). The stability, compositions and lattice structures of the intermetallic compounds of Mg-Zn-La alloys were identified. The results show that, there exists a ternary compound (T-phase) with constant La (about 8at%) and the changed ratio of Mg/Zn in the Mg-rich corner of Mg-Zn-La system. Though the ratio of (Mg, Zn)/La of T-phase is close to that of Mg/La of Mg12La, the T-phase was not the binary solid solution of Mg12La because of the difference of the lattice structure. It also reveals that T-phase is a stable phase, and it is in two-phase equilibrium of T-phase+Mg at 150°C.

Isomorphous replacement in electron diffraction of wet crystals of rat hemoglobin

1983 ◽  
Vol 41 ◽  
pp. 446-447
Author(s):  
William F. Tivol ◽  
Murray Vernon King ◽  
D. F. Parsons
Keyword(s):  
Electron Diffraction ◽  
Heavy Atom ◽  
Isomorphous Substitution ◽  
X Ray Diffraction ◽  
Salt Solutions ◽  
X Ray ◽  
Isomorphous Replacement ◽  
Structure Factors ◽  
Diffraction Structure ◽  
The Mean

Feasibility of isomorphous substitution in electron diffraction is supported by a calculation of the mean alteration of the electron-diffraction structure factors for hemoglobin crystals caused by substituting two mercury atoms per molecule, following Green, Ingram & Perutz, but with allowance for the proportionality of f to Z3/4 for electron diffraction. This yields a mean net change in F of 12.5%, as contrasted with 22.8% for x-ray diffraction.Use of the hydration chamber in electron diffraction opens prospects for examining many proteins that yield only very thin crystals not suitable for x-ray diffraction. Examination in the wet state avoids treatments that could cause translocation of the heavy-atom labels or distortion of the crystal. Combined with low-fluence techniques, it enables study of the protein in a state as close to native as possible.We have undertaken a study of crystals of rat hemoglobin by electron diffraction in the wet state. Rat hemoglobin offers a certain advantage for hydration-chamber work over other hemoglobins in that it can be crystallized from distilled water instead of salt solutions.

Fractionation of polymethylene chains: An electron crystallographic investigation

1986 ◽  
Vol 44 ◽  
pp. 794-795
Author(s):  
Douglas L. Dorset
Keyword(s):  
Cross Section ◽  
Binary Systems ◽  
Linear Chain ◽  
Pure Component ◽  
Organic Substrates ◽  
Crystallographic Investigation ◽  
X Ray Diffraction ◽  
X Ray ◽  
Molecular Sizes ◽  
The Stability

A variety of linear chain materials exist as polydisperse systems which are difficultly purified. The stability of continuous binary solid solutions assume that the Gibbs free energy of the solution is lower than that of either crystal component, a condition which includes such factors as relative molecular sizes and shapes and perhaps the symmetry of the pure component crystal structures.Although extensive studies of n-alkane miscibility have been carried out via powder X-ray diffraction of bulk samples we have begun to examine binary systems as single crystals, taking advantage of the well-known enhanced scattering cross section of matter for electrons and also the favorable projection of a paraffin crystal structure posited by epitaxial crystallization of such samples on organic substrates such as benzoic acid.

scholarly journals A Superhydrophobic, Antibacterial, and Durable Surface of Poplar Wood

Nanomaterials ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1885
Author(s):  
Xinyu Wu ◽  
Feng Yang ◽  
Jian Gan ◽  
Zhangqian Kong ◽  
Yan Wu
Keyword(s):  
Stearic Acid ◽  
Antibacterial Properties ◽  
Alkali Resistance ◽  
Poplar Wood ◽  
X Ray Diffraction ◽  
X Ray ◽  
Different Temperatures ◽  
Acid And Alkali Resistance ◽  
The Stability

The silver particles were grown in situ on the surface of wood by the silver mirror method and modified with stearic acid to acquire a surface with superhydrophobic and antibacterial properties. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and X-ray energy spectroscopy (XPS) were used to analyze the reaction mechanism of the modification process. Scanning electron microscopy (SEM) and contact angle tests were used to characterize the wettability and surface morphology. A coating with a micro rough structure was successfully constructed by the modification of stearic acid, which imparted superhydrophobicity and antibacterial activity to poplar wood. The stability tests were performed to discuss the stability of its hydrophobic performance. The results showed that it has good mechanical properties, acid and alkali resistance, and UV stability. The durability tests demonstrated that the coating has the function of water resistance and fouling resistance and can maintain the stability of its hydrophobic properties under different temperatures of heat treatment.

scholarly journals Synthesis of Bis(Carboranyl)amides 1,1′-μ-(CH2NH(O)C(CH2)n-1,2-C2B10H11)2 (n = 0, 1) and Attempt of Synthesis of Gadolinium Bis(Dicarbollide)

Molecules ◽  
2021 ◽  
Vol 26 (5) ◽  
pp. 1321
Author(s):  
Yasunobu Asawa ◽  
Aleksandra V. Arsent’eva ◽  
Sergey A. Anufriev ◽  
Alexei A. Anisimov ◽  
Kyrill Yu. Suponitsky ◽  
...  
Keyword(s):  
Molecular Structure ◽  
Single Crystal ◽  
Quantum Chemical Calculations ◽  
Quantum Chemical ◽  
X Ray Diffraction ◽  
Stable Conformation ◽  
Acyl Chlorides ◽  
X Ray ◽  
Cesium Fluoride ◽  
The Stability

Bis(carboranyl)amides 1,1′-μ-(CH2NH(O)C(CH2)n-1,2-C2B10H11)2 (n = 0, 1) were prepared by the reactions of the corresponding carboranyl acyl chlorides with ethylenediamine. Crystal molecular structure of 1,1′-μ-(CH2NH(O)C-1,2-C2B10H11)2 was determined by single crystal X-ray diffraction. Treatment of bis(carboranyl)amides 1,1′-μ-(CH2NH(O)C(CH2)n-1,2-C2B10H11)2 with ammonium or cesium fluoride results in partial deboronation of the ortho-carborane cages to the nido-carborane ones with formation of [7,7′(8′)-μ-(CH2NH(O)C(CH2)n-7,8-C2B9H11)2]2−. The attempted reaction of [7,7′(8′)-μ-(CH2NH(O)CCH2-7,8-C2B9H11)2]2− with GdCl3 in 1,2-dimethoxy- ethane did not give the expected metallacarborane. The stability of different conformations of Gd-containing metallacarboranes has been estimated by quantum-chemical calculations using [3,3-μ-DME-3,3′-Gd(1,2-C2B9H11)2]− as a model. It was found that in the most stable conformation the CH groups of the dicarbollide ligands are in anti,anti-orientation with respect to the DME ligand, while any rotation of the dicarbollide ligand reduces the stability of the system. This makes it possible to rationalize the design of carborane ligands for the synthesis of gadolinium metallacarboranes on their base.

scholarly journals Facile Organometallic Synthesis of Fe-Based Nanomaterials by Hot Injection Reaction

Nanomaterials ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 1141
Author(s):  
Georgia Basina ◽  
Hafsa Khurshid ◽  
Nikolaos Tzitzios ◽  
George Hadjipanayis ◽  
Vasileios Tzitzios
Keyword(s):  
Room Temperature ◽  
Colloidal Particles ◽  
Iron Pentacarbonyl ◽  
Vibrating Sample Magnetometer ◽  
X Ray Diffraction ◽  
Organometallic Synthesis ◽  
X Ray ◽  
Transmission Electron ◽  
Hot Injection ◽  
The Stability

Fe-based colloids with a core/shell structure consisting of metallic iron and iron oxide were synthesized by a facile hot injection reaction of iron pentacarbonyl in a multi-surfactant mixture. The size of the colloidal particles was affected by the reaction temperature and the results demonstrated that their stability against complete oxidation related to their size. The crystal structure and the morphology were identified by powder X-ray diffraction and transmission electron microscopy, while the magnetic properties were studied at room temperature with a vibrating sample magnetometer. The injection temperature plays a very crucial role and higher temperatures enhance the stability and the resistance against oxidation. For the case of injection at 315 °C, the nanoparticles had around a 10 nm mean diameter and revealed 132 emu/g. Remarkably, a stable dispersion was created due to the colloids’ surface functionalization in a nonpolar solvent.

scholarly journals Study of Corrosion Resistance and Degradation Mechanisms in LiTiO2-Li2TiO3 Ceramic

Crystals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 753
Author(s):  
Dmitriy Shlimas ◽  
Artem L. Kozlovskiy ◽  
Maxim Zdorovets
Keyword(s):  
Degradation Mechanism ◽  
Diffraction Method ◽  
Large Mass ◽  
Time Frame ◽  
X Ray Diffraction ◽  
Acidic Media ◽  
X Ray ◽  
Mass Losses ◽  
The Stability ◽  
Thermal Sintering

The interest in lithium-containing ceramics is due to their huge potential as blanket materials for thermonuclear reactors for the accumulation of tritium. However, an important factor in their use is the preservation of the stability of their strength and structural properties when under the influence of external factors that determine the time frame of their operation. This paper presents the results of a study that investigated the influence of the LiTiO2 phase on the increasing resistance to degradation and corrosion of Li2TiO3 ceramic when exposed to aggressive acidic media. Using the X-ray diffraction method, it was found that an increase in the concentration of LiClO4·3H2O during synthesis leads to the formation of a cubic LiTiO2 phase in the structure as a result of thermal sintering of the samples. During corrosion tests, it was found that the presence of the LiTiO2 phase leads to a decrease in the degradation rate in acidic media by 20–70%, depending on the concentration of the phase. At the same time, and in contrast to the samples of Li2TiO3 ceramics, for which the mechanisms of degradation during a long stay in aggressive media are accompanied by large mass losses, for the samples containing the LiTiO2 phase, the main degradation mechanism is pitting corrosion with the formation of pitting inclusions.

Polydomain Structure of Epitaxial PbTiO3 films on MgO

1997 ◽  
Vol 493 ◽  
Author(s):  
S. P. Alpay ◽  
A. S. Prakash ◽  
S. Aggarwal ◽  
R. Ramesh ◽  
A. L. Roytburd ◽  
...  
Keyword(s):  
Domain Structure ◽  
Pulsed Laser ◽  
Laser Deposition ◽  
X Ray Diffraction ◽  
X Ray ◽  
Theoretical Predictions ◽  
The Stability ◽  
Increasing Temperature ◽  
Stable Domains ◽  
Domain Stability

ABSTRACTA PbTiO3(001) film grown on MgO(001) by pulsed laser deposition is examined as an example to demonstrate the applications of the domain stability map for epitaxial perovskite films which shows regions of stable domains and fractions of domains in a polydomain structure. X-ray diffraction studies indicate that the film has a …c/a/c/a… domain structure in a temperature range of °C to 400°C with the fraction of c-domains decreasing with increasing temperature. These experimental results are in excellent agreement with theoretical predictions based on the stability map.

scholarly journals High temperature structural study of decagonal Al-Cu-Rh quasicrystal.

2014 ◽  
Vol 70 (a1) ◽  
pp. C94-C94
Author(s):  
Pawel Kuczera ◽  
Walter Steurer
Keyword(s):  
Structural Changes ◽  
Configurational Entropy ◽  
Lattice Vibrations ◽  
X Ray Diffraction ◽  
Stabilization Mechanism ◽  
X Ray ◽  
Comparative Structure ◽  
The Stability

The structure of d(ecagonal)-Al-Cu-Rh has been studied as a function of temperature by in-situ single-crystal X-ray diffraction in order to contribute to the discussion on energy or entropy stabilization of quasicrystals (QC) [1]. The experiments were performed at 293 K, 1223 K, 1153 K, 1083 K, and 1013 K. A common subset of 1460 unique reflections was used for the comparative structure refinements at each temperature. The results obtained for the HT structure refinements of d-Al-Cu-Rh QC seem to contradict a pure phasonic-entropy-based stabilization mechanism [2] for this QC. The trends observed for the ln func(I(T1 )/I(T2 )) vs.|k⊥ |^2 plots indicate that the best on-average quasiperiodic order exists between 1083 K and 1153 K, however, what that actually means is unclear. It could indicate towards a small phasonic contribution to entropy, but such contribution is not seen in the structure refinements. A rough estimation of the hypothetic phason instability temperature shows that it would be kinetically inaccessible and thus the phase transition to a 12 Å low T structure (at ~800 K) is most likely not phason-driven. Except for the obvious increase in the amplitude of the thermal motion, no other significant structural changes, in particular no sources of additional phason-related configurational entropy, were found. All structures are refined to very similar R-values, which proves that the quality of the refinement at each temperature is the same. This suggests, that concerning the stability factors, some QCs could be similar to other HT complex intermetallic phases. The experimental results clearly show that at least the ~4 Å structure of d-Al-Cu-Rh is a HT phase therefore entropy plays an important role in its stabilisation mechanism lowering the free energy. However, the main source of this entropy is probably not related to phason flips, but rather to lattice vibrations, occupational disorder unrelated to phason flips like split positions along the periodic axis.

Study on Influence of Silicate Morphology Based on pH Value

2012 ◽  
Vol 454 ◽  
pp. 324-328
Author(s):  
Yan He ◽  
Ya Jing Liu ◽  
Yong Lin Cao ◽  
Li Xia Zhou
Keyword(s):  
Silicic Acid ◽  
Ph Value ◽  
Colorimetric Method ◽  
Absorption Spectrometry ◽  
Degree Of Polymerization ◽  
Raw Material ◽  
X Ray Diffraction ◽  
X Ray ◽  
Ph Values ◽  
The Stability

Infra-red absorption spectrometry, X-ray diffraction observations and characterization tests based on silicon molybdenum colorimetric method were used to investigate the optimal pH value controlling the stability of the silicic acid form. The experiment process was done by using sodium silicate as raw material. The results showed that the solution of silicate influenced the polymerization. The active silicic acid solution with a certain degree of polymerization was obtained by controlling the pH values.

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