scholarly journals Structure of the DMPC lipid bilayer ripple phase

Soft Matter ◽  
2015 ◽  
Vol 11 (5) ◽  
pp. 918-926 ◽  
Author(s):  
Kiyotaka Akabori ◽  
John F. Nagle
Keyword(s):  
High Resolution ◽  
Lipid Bilayer ◽  
Lipid Bilayers ◽  
X Ray ◽  
Ripple Phase

High resolution X-ray study provides new insight for the enigmatic ripple phase in lipid bilayers.

scholarly journals Visualization of lipid bilayer in the crystals by solvent contrast modulation

2014 ◽  
Vol 70 (a1) ◽  
pp. C1498-C1498
Author(s):  
Yoshiyuki Norimatsu ◽  
Junko Tsueda ◽  
Ayami Hirata ◽  
Shiho Iwasawa ◽  
Chikashi Toyoshima
Keyword(s):  
Lipid Bilayer ◽  
Electron Density ◽  
Lipid Bilayers ◽  
Transmembrane Helix ◽  
Real Space ◽  
New Method ◽  
Imaging Plate ◽  
Salt Bridges ◽  
Transmembrane Helices ◽  
X Ray

A new method of X-ray solvent contrast modulation was developed to visualize lipid bilayers in crystals of membrane proteins at a high enough resolution to resolve individual phospholipids molecules (~3.5 Å ). Visualization of lipid bilayer has been escaping from conventional crystallographic methods due to its extreme flexibility, and our knowledge on the behavior of lipid bilayer is still very much limited. Here we applied the new method of X-ray solvent contrast modulation to crystals of Ca2+-ATPase in 4 different physiological states. As phospholipids have to be added to make crystals of Ca2+-ATPase, it is expected that lipid bilayers are present in the crystals. Moreover, transmembrane helices of Ca2+-ATPase rearrange drastically during the reaction cycle and some of them show substantial movements perpendicular to the bilayer plane. Thus these crystals provide a rare opportunity to directly visualize phospholipids interacting with a membrane protein in different conformations. Complete diffraction data covering from 200 to 3.2 Å resolution were collected at BL41XU, Spring-8, using an R-Axis V imaging plate detector for crystals soaked in solvent of different electron density. A new concept "solvent exchange probability", which should be 1 in the bulk solvent, 0 inside the protein and an intermediate at interface, was introduced and used as a restraint for real space phase improvement. The electron density maps thus obtained clearly show that: (i) Phospholipid molecules surrounding the protein are fixed apparently by Arg/Lys-phosphate salt bridges or Trp-carbonyl hydrogen bonds and follow the movements of transmembrane helices. Movements of as large as 12 Å are allowed. (ii) If the movement of a transmembrane helix exceeds this limit, associated phospholipids change the partners for fixation or change the orientation of the entire protein molecule.

Studies of short-wavelength collective molecular motions in lipid bilayers using high resolution inelastic X-ray scattering

2003 ◽  
Vol 105 (2-3) ◽  
pp. 721-741 ◽  
Author(s):  
Poe-Jou Chen ◽  
Yun Liu ◽  
Thomas M. Weiss ◽  
Huey W. Huang ◽  
Harald Sinn ◽  
...  
Keyword(s):  
High Resolution ◽  
Lipid Bilayers ◽  
Short Wavelength ◽  
Molecular Motions ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

BILMIX: a new approach to restore the size polydispersity and electron density profiles of lipid bilayers from liposomes using small-angle X-ray scattering data

2020 ◽  
Vol 53 (1) ◽  
pp. 236-243
Author(s):  
Petr V. Konarev ◽  
Maxim V. Petoukhov ◽  
Liubov A. Dadinova ◽  
Natalia V. Fedorova ◽  
Pavel E. Volynsky ◽  
...  
Keyword(s):  
Lipid Bilayer ◽  
Electron Density ◽  
Lipid Bilayers ◽  
Density Profile ◽  
Small Angle ◽  
Electron Density Profile ◽  
Scattering Data ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

Small-angle X-ray scattering (SAXS) is one of the major tools for the study of model membranes, but interpretation of the scattering data remains non-trivial. Current approaches allow the extraction of some structural parameters and the electron density profile of lipid bilayers. Here it is demonstrated that parametric modelling can be employed to determine the polydispersity of spherical or ellipsoidal vesicles and describe the electron density profile across the lipid bilayer. This approach is implemented in the computer program BILMIX. BILMIX delivers a description of the electron density of a lipid bilayer from SAXS data and simultaneously generates the corresponding size distribution of the unilamellar lipid vesicles.

Electron microscopy of rabbit FC crystals

1983 ◽  
Vol 41 ◽  
pp. 730-731
Author(s):  
Robert A. Grant ◽  
Laura L. Degn ◽  
Wah Chiu ◽  
John Robinson
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
High Resolution Electron Microscopy ◽  
Molecular Replacement ◽  
X Ray ◽  
X Ray Crystallography ◽  
Resolution Electron ◽  
Replacement Technique ◽  
Hydrated Crystal ◽  
Molecular Structure Analysis

Proteolytic digestion of the immunoglobulin IgG with papain cleaves the molecule into an antigen binding fragment, Fab, and a compliment binding fragment, Fc. Structures of intact immunoglobulin, Fab and Fc from various sources have been solved by X-ray crystallography. Rabbit Fc can be crystallized as thin platelets suitable for high resolution electron microscopy. The structure of rabbit Fc can be expected to be similar to the known structure of human Fc, making it an ideal specimen for comparing the X-ray and electron crystallographic techniques and for the application of the molecular replacement technique to electron crystallography. Thin protein crystals embedded in ice diffract to high resolution. A low resolution image of a frozen, hydrated crystal can be expected to have a better contrast than a glucose embedded crystal due to the larger density difference between protein and ice compared to protein and glucose. For these reasons we are using an ice embedding technique to prepare the rabbit Fc crystals for molecular structure analysis by electron microscopy.

High Resolution Study of Polytypism: Application to SiC and Au3 Mn

1982 ◽  
Vol 40 ◽  
pp. 540-541
Author(s):  
G. Van Tendeloo ◽  
J. Van Landuyt ◽  
S. Amelinckx
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Stacking Sequence ◽  
X Ray ◽  
Powerful Technique ◽  
Resolution Study ◽  
The Ideal

Polytypism has been studied for a number of years and a wide variety of stacking sequences has been detected and analysed. SiC is the prototype material in this respect; see e.g. Electron microscopy under high resolution conditions when combined with x-ray measurements is a very powerful technique to elucidate the correct stacking sequence or to study polytype transformations and deviations from the ideal stacking sequence.

A High Resolution Study of G.P. Zones in Aluminum - 4.2 at % Silver

1982 ◽  
Vol 40 ◽  
pp. 722-723 ◽  
Author(s):  
R. Gronsky
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Computer Simulations ◽  
Structural Characteristics ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Resolution Study

The phenomenon of clustering in Al-Ag alloys has been extensively studied since the early work of Guinierl, wherein the pre-precipitation state was characterized as an assembly of spherical, ordered, silver-rich G.P. zones. Subsequent x-ray and TEM investigations yielded results in general agreement with this model. However, serious discrepancies were later revealed by the detailed x-ray diffraction - based computer simulations of Gragg and Cohen, i.e., the silver-rich clusters were instead octahedral in shape and fully disordered, atleast below 170°C. The object of the present investigation is to examine directly the structural characteristics of G.P. zones in Al-Ag by high resolution transmission electron microscopy.

Scanning Electron Microscopy and x-ray analysis of microparticles and early hydration effects

1995 ◽  
Vol 53 ◽  
pp. 692-693
Author(s):  
Yun Lu ◽  
David C. Joy
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
High Resolution ◽  
Morphological Development ◽  
Early Hydration ◽  
X Ray ◽  
Blended Cements ◽  
Powder Particles ◽  
Chemical Wastes ◽  
Scanning Electron

High resolution scanning electron microscopy (SEM) and energy dispersive x-ray analysis (EDXA) were performed to investigate microparticles in blended cements and their hydration products containing sodium-rich chemical wastes. The physical appearance of powder particles and the morphological development at different hydration stages were characterized by using high resolution SEM Hitachi S-900 and by SEM S-800 with a EDX spectrometer. Microparticles were dispersed on the sample holder and glued by 1% palomino solution. Hydrated bulk samples were dehydrated by acetone and mounted on the holder by silver paste. Both fracture surfaces and flat cutting sections of hydrating samples were prepared and examined. Some specimens were coated with an 3 nm thick Au-Pd or Cr layer to provide good conducting surfaces. For high resolution SEM S-900 observations the accelerating voltage of electrons was 1-2 KeV to protect the electron charging. Microchemical analyses were carried out by S800/EDS equipped with a LINK detector of take-off angle =40°.

Tubulin structure at intermediate resolution

1995 ◽  
Vol 53 ◽  
pp. 852-853
Author(s):  
K. H. Downing ◽  
S. G. Wolf ◽  
E. Nogales
Keyword(s):  
High Resolution ◽  
Structural Data ◽  
Therapeutic Drug ◽  
Zinc Ions ◽  
Two Dimensional ◽  
X Ray Diffraction ◽  
X Ray ◽  
Negative Stain ◽  
Functional Mechanisms ◽  
Tubulin Structure

Microtubules are involved in a host of critical cell activities, many of which involve transport of organelles through the cell. Different sets of microtubules appear to form during the cell cycle for different functions. Knowledge of the structure of tubulin will be necessary in order to understand the various functional mechanisms of microtubule assemble, disassembly, and interaction with other molecules, but tubulin has so far resisted crystallization for x-ray diffraction studies. Fortuitously, in the presence of zinc ions, tubulin also forms two-dimensional, crystalline sheets that are ideally suited for study by electron microscopy. We have refined procedures for forming the sheets and preparing them for EM, and have been able to obtain high-resolution structural data that sheds light on the formation and stabilization of microtubules, and even the interaction with a therapeutic drug.Tubulin sheets had been extensively studied in negative stain, demonstrating that the same protofilament structure was formed in the sheets and microtubules. For high resolution studies, we have found that the sheets embedded in either glucose or tannin diffract to around 3 Å.

Nano-probe x-ray analysis and high-resolution imaging on planar defects in high-pressure synthesized infinite-layer superconductor

1994 ◽  
Vol 52 ◽  
pp. 728-729
Author(s):  
Y. Y. Wang ◽  
H. Zhang ◽  
V. P. Dravid ◽  
H. Zhang ◽  
L. D. Marks ◽  
...  
Keyword(s):  
High Pressure ◽  
High Resolution ◽  
Atomic Structure ◽  
Emission Spectra ◽  
High Resolution Electron Microscopy ◽  
Planar Defects ◽  
X Ray ◽  
Infinite Layer ◽  
Resolution Electron ◽  
Resolution Imaging

Azuma et al. observed planar defects in a high pressure synthesized infinitelayer compound (i.e. ACuO2 (A=cation)), which exhibits superconductivity at ~110 K. It was proposed that the defects are cation deficient and that the superconductivity in this material is related to the planar defects. In this report, we present quantitative analysis of the planar defects utilizing nanometer probe xray microanalysis, high resolution electron microscopy, and image simulation to determine the chemical composition and atomic structure of the planar defects. We propose an atomic structure model for the planar defects.Infinite-layer samples with the nominal chemical formula, (Sr1-xCax)yCuO2 (x=0.3; y=0.9,1.0,1.1), were prepared using solid state synthesized low pressure forms of (Sr1-xCax)CuO2 with additions of CuO or (Sr1-xCax)2CuO3, followed by a high pressure treatment.Quantitative x-ray microanalysis, with a 1 nm probe, was performed using a cold field emission gun TEM (Hitachi HF-2000) equipped with an Oxford Pentafet thin-window x-ray detector. The probe was positioned on the planar defects, which has a 0.74 nm width, and x-ray emission spectra from the defects were compared with those obtained from vicinity regions.

Characterisation of planar crystal defects in Y2Fe17Cx (0.6 ≤ x ≤ 1.6) magnetic material by High Resolution Electron Microscopy

1990 ◽  
Vol 48 (4) ◽  
pp. 774-775
Author(s):  
W. Coene ◽  
F. Hakkens ◽  
T.H. Jacobs ◽  
K.H.J. Buschow
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Permanent Magnets ◽  
Annealing Treatment ◽  
High Resolution Electron Microscopy ◽  
Crystal Defects ◽  
Ordered Structure ◽  
X Ray ◽  
Planar Crystal ◽  
Resolution Electron

Intermetallic compounds of the type RE2Fe17Cx (RE= rare earth element) are promising candidates for permanent magnets. In case of Y2Fe17Cx, the Curie temperature increases from 325 K for x =0 to 550 K for x = 1.6 . X ray and electron diffraction reveal a carbon - induced structural transformation in Y2Fe17Cx from the hexagonal Th2Ni17 - type (x < 0.6 ) to the rhombohedral Th2Zn17 - type ( x ≥ 0.6). Planar crystal defects introduce local sheets of different magnetic anisotropy as compared with the ordered structure, and therefore may have an important impact on the coercivivity mechanism .High resolution electron microscopy ( HREM ) on a Philips CM30 / Super Twin has been used to characterize planar crystal defects in rhombohedral Y2Fe17Cx ( x ≥ 0.6 ). The basal plane stacking sequences are imaged in the [100] - orientation, showing an ABC or ACB sequence of Y - atoms and Fe2 - dumbbells, for both coaxial twin variants, respectively . Compounds resulting from a 3 - week annealing treatment at high temperature ( Ta = 1000 - 1100°C ) contain a high density of planar defects.

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