2005 Vol. 29, No. S1
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Abstract:
Alamethicin is a 20-amino acid membrane-active peptide from the fungus Trichoderma viride that spontaneously inserts into lipid membranes and self-associates into transmembrane channels. It has an antimicrobial activity against fungi and Gram-positive bacteria. We have investigated the effect of the peptide on the structure of lipid membranes by X-ray scattering method. The highly aligned stacks of membranes were prepared by evaporation of organic solutions of alamethicin and 1,2-dioleoyl-sn-glycero-3-phosphocholine deposited on clean silicon surfaces and were immersed in excess ultra pure water. The in-situ X-ray measurements show that the membranes with inserted peptides become thinner and softer at high molar peptide/lipid ratio.
Alamethicin is a 20-amino acid membrane-active peptide from the fungus Trichoderma viride that spontaneously inserts into lipid membranes and self-associates into transmembrane channels. It has an antimicrobial activity against fungi and Gram-positive bacteria. We have investigated the effect of the peptide on the structure of lipid membranes by X-ray scattering method. The highly aligned stacks of membranes were prepared by evaporation of organic solutions of alamethicin and 1,2-dioleoyl-sn-glycero-3-phosphocholine deposited on clean silicon surfaces and were immersed in excess ultra pure water. The in-situ X-ray measurements show that the membranes with inserted peptides become thinner and softer at high molar peptide/lipid ratio.
Abstract:
We report on the synchrotron small-angle X-ray scattering (SAXS) study of self-assembled complex formed by mixing short-chain DNAs with cationic phospholipids in water. The DNA/lipid complex is a sandwiched structure, consisting of alternate layers of DNAs and lipid bilayers with a periodicity of dD/L. The DNAs at the interfaces are one-dimensionally ordered with a periodicity of dDNA. When the temperature of the system is increased, the lipid bilayers become soft so that the DNAs are trapped more deeply inside the lipid bilayers. This explains why the measured dD/Ldecreases insignificantly with the increase of temperature.On the other hand, the value of dDNAkeeps constant because of the stiffness of the DNAs.
We report on the synchrotron small-angle X-ray scattering (SAXS) study of self-assembled complex formed by mixing short-chain DNAs with cationic phospholipids in water. The DNA/lipid complex is a sandwiched structure, consisting of alternate layers of DNAs and lipid bilayers with a periodicity of dD/L. The DNAs at the interfaces are one-dimensionally ordered with a periodicity of dDNA. When the temperature of the system is increased, the lipid bilayers become soft so that the DNAs are trapped more deeply inside the lipid bilayers. This explains why the measured dD/Ldecreases insignificantly with the increase of temperature.On the other hand, the value of dDNAkeeps constant because of the stiffness of the DNAs.
Abstract:
The morphology of a series of well-defined graft copolymers of diacetate cellulose and PMMA was studied through SR-SAXS. The graft copolymer formed mono-molecular sphere in the solution of CCl2H2and CH3OH. And the dimension of the graft copolymer increased with the increasing of the degree of polymerization of the PMMA side chains.
The morphology of a series of well-defined graft copolymers of diacetate cellulose and PMMA was studied through SR-SAXS. The graft copolymer formed mono-molecular sphere in the solution of CCl2H2and CH3OH. And the dimension of the graft copolymer increased with the increasing of the degree of polymerization of the PMMA side chains.
Abstract:
Encapsulated cytochrome c Sol-Gel materials was synthesis and studied by UV-vis absorption spectra and SAXS. It was illuminated that exist a lower effective pH within TMOS-derived sgel by monitoring wavelengh shifts in the peak absorption of the Soret band. The gyration radius of encapsulated cytochrome c within gel was calculation by SAXS.
Encapsulated cytochrome c Sol-Gel materials was synthesis and studied by UV-vis absorption spectra and SAXS. It was illuminated that exist a lower effective pH within TMOS-derived sgel by monitoring wavelengh shifts in the peak absorption of the Soret band. The gyration radius of encapsulated cytochrome c within gel was calculation by SAXS.
Abstract:
The structures of [Ni70Co30(25A)/Cu(20A)]20multilayers were investigated by X-ray anomalous scattering technique. Different structural behaviors at the Cu/Ni70Co30and Ni70Co30/Cu interfaces were obtained respectively.For the as-deposited sample, the interfaces are asymmetrical. An 8A thick CuNi3and a 4A thick NiCo layers are observed at the Cu/Ni70Co30interface, however the Ni70Co30/Cu interface is sharp. For the annealed sample, the sharp Ni70Co30/Cu interface is replaced by a CuNi2Co sublayer of about 12A thick. The X-ray diffuse scattering experiments, performed with the incident X-ray energy close to the Co, Ni and Cu K edges respectively, show the distribution of Co, Ni and Cu at the interfaces is not uniform.
The structures of [Ni70Co30(25A)/Cu(20A)]20multilayers were investigated by X-ray anomalous scattering technique. Different structural behaviors at the Cu/Ni70Co30and Ni70Co30/Cu interfaces were obtained respectively.For the as-deposited sample, the interfaces are asymmetrical. An 8A thick CuNi3and a 4A thick NiCo layers are observed at the Cu/Ni70Co30interface, however the Ni70Co30/Cu interface is sharp. For the annealed sample, the sharp Ni70Co30/Cu interface is replaced by a CuNi2Co sublayer of about 12A thick. The X-ray diffuse scattering experiments, performed with the incident X-ray energy close to the Co, Ni and Cu K edges respectively, show the distribution of Co, Ni and Cu at the interfaces is not uniform.
Abstract:
La0.7Ca0.3MnO3(LCMO) thin films with the thickness ranging from 5 nm to 200 nm were deposited on (001)-oriented single crystal MgO substrate by 90° off-axis radio frequency magnetron sputtering. Grazing incidence X-ray diffraction technique, combined with normal X-ray diffraction, was applied to study the lattice strain and strain relaxation in LCMO films. The magnetoresistance of films were measured by means of standard four-probe technique. The results indicated that the microstrain of LCMO/MgO film began to relax when the film thickness is less than 5 nm. The LCMO film is fully strain-relaxed with thickness larger than 100 nm and exhibit LCMO bulk-like magnetoresistance properties, i.e. with relatively lager magnetoresistance ratio and higher peak temperature of magnetoresistance.
La0.7Ca0.3MnO3(LCMO) thin films with the thickness ranging from 5 nm to 200 nm were deposited on (001)-oriented single crystal MgO substrate by 90° off-axis radio frequency magnetron sputtering. Grazing incidence X-ray diffraction technique, combined with normal X-ray diffraction, was applied to study the lattice strain and strain relaxation in LCMO films. The magnetoresistance of films were measured by means of standard four-probe technique. The results indicated that the microstrain of LCMO/MgO film began to relax when the film thickness is less than 5 nm. The LCMO film is fully strain-relaxed with thickness larger than 100 nm and exhibit LCMO bulk-like magnetoresistance properties, i.e. with relatively lager magnetoresistance ratio and higher peak temperature of magnetoresistance.
Abstract:
This study systematically addresses the effect of temperature on the growth of SiGe compliant substrates. The characteristics of the films were experimentally determined by various techniques, including high resolution X-ray diffraction (HRXRD), surface diffraction, X-ray reflectivity with synchrotron radiation,transmission electron microscopy (TEM) and atomic force microscopy (AFM).In the growth temperature range from 350—600\textcelsius, X-ray diffraction shows that the film was strain relaxed with a Ge content of 32±2%, and TEM indicates that the film is free from dislocations in the temperature range, 400—500\textcelsius.AFM reveals that the optimal temperature for the growth is 450\textcelsius, with a root mean squared surface roughness of 15\AA.
This study systematically addresses the effect of temperature on the growth of SiGe compliant substrates. The characteristics of the films were experimentally determined by various techniques, including high resolution X-ray diffraction (HRXRD), surface diffraction, X-ray reflectivity with synchrotron radiation,transmission electron microscopy (TEM) and atomic force microscopy (AFM).In the growth temperature range from 350—600\textcelsius, X-ray diffraction shows that the film was strain relaxed with a Ge content of 32±2%, and TEM indicates that the film is free from dislocations in the temperature range, 400—500\textcelsius.AFM reveals that the optimal temperature for the growth is 450\textcelsius, with a root mean squared surface roughness of 15\AA.
Abstract:
Three sets of Co/W bilayers with varying Co and/or W layer thickness were prepared by d.c. magnetosputtering technique. The magnetic properties of Co/W bilayers have been investigated using ferromagnetic resonance (FMR) and vibrating sample magnetomete.Specular X-ray reflectivity and high angle X-ray diffraction were used to characterize the structure of the deposited samples. The saturation magnetization of Co increased with Co thickness but was smaller than that of bulk hcp Co. The larger interface roughness and FMR line-width for the thinner Co/W films indicate the inhomogeneity of Co and/or W layers.
Three sets of Co/W bilayers with varying Co and/or W layer thickness were prepared by d.c. magnetosputtering technique. The magnetic properties of Co/W bilayers have been investigated using ferromagnetic resonance (FMR) and vibrating sample magnetomete.Specular X-ray reflectivity and high angle X-ray diffraction were used to characterize the structure of the deposited samples. The saturation magnetization of Co increased with Co thickness but was smaller than that of bulk hcp Co. The larger interface roughness and FMR line-width for the thinner Co/W films indicate the inhomogeneity of Co and/or W layers.