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Vinchurkar MS Bricarello DA Lagerstedt JO Buban JP Stahlberg H Oda MN Voss JC Parikh AN 《Journal of the American Chemical Society》2008,130(33):11164-11169
We show that a two-step process, involving spontaneous self-assembly of lipids and apolipoproteins and surface patterning, produces single, supported lipid bilayers over two discrete and independently adjustable length scales. Specifically, an aqueous phase incubation of DMPC vesicles with purified apolipoprotein A-I results in the reconstitution of high density lipoprotein (rHDL), wherein nanoscale clusters of single lipid bilayers are corralled by the protein. Adsorption of these discoidal particles to clean hydrophilic glass (or silicon) followed by direct exposure to a spatial pattern of short-wavelength UV radiation directly produces microscopic patterns of nanostructured bilayers. Alternatively, simple incubation of aqueous phase rHDL with a chemically patterned hydrophilic/hydrophobic surface produces a novel compositional pattern, caused by an increased affinity for adsorption onto hydrophilic regions relative to the surrounding hydrophobic regions. Further, by simple chemical denaturation of the boundary protein, nanoscale compartmentalization can be selectively erased, thus producing patterns of laterally fluid, lipid bilayers structured solely at the mesoscopic length scale. Since these aqueous phase microarrays of nanostructured lipid bilayers allow for membrane proteins to be embedded within single nanoscale bilayer compartments, they present a viable means of generating high-density membrane protein arrays. Such a system would permit in-depth elucidation of membrane protein structure-function relationships and the consequences of membrane compartmentalization on lipid dynamics. 相似文献
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In this paper we demonstrate the use of the multiple scattering methodology to interpret oxygen K-edge spectra from both the bulk and grain boundaries in a variety of ceramic oxides. The experimental electron energy loss spectra (EELS) used in this study, were obtained from a dedicated scanning transmission electron microscope (STEM). Using the STEM to obtain the spectra has the advantage that each spectrum can be acquired with atomic spatial resolution. While the energy resolution is limited to approximately 0.8 eV, and the angular integration in the microscope apertures precludes momentum resolved spectroscopy, this unprecedented spatial resolution allows the electronic structure at individual defect sites to be determined. Additionally, as the microscope can also provide an atomic resolution image of the defect, the relationship between the atomic structure of the defect and its local electronic structure can be determined. In practice, this is achieved by using the structure observed in the image to build the real space atomic cluster for multiple scattering simulations. Detailed interpretation of the simulations of oxygen K-edge spectra from bulk MgO, CaO, SrTiO3, TiO2, MnO2, Mn3O4, Mn2O3 and MnO are presented. In addition, the simulations from grain boundaries in TiO2 (undoped) and SrTiO3 (undoped and Mn doped) are discussed in relation to quantifying the changes in the local electronic structure that are a direct consequence of the defect structure. The simulations are used to make interpretations of the structure-property relationships at these grain boundaries. 相似文献
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Ogale SB Choudhary RJ Buban JP Lofland SE Shinde SR Kale SN Kulkarni VN Higgins J Lanci C Simpson JR Browning ND Das Sarma S Drew HD Greene RL Venkatesan T 《Physical review letters》2003,91(7):077205
The occurrence of room temperature ferromagnetism is demonstrated in pulsed laser deposited thin films of Sn(1-x)Co(x)O(2-delta) (x<0.3). Interestingly, films of Sn(0.95)Co(0.05)O(2-delta) grown on R-plane sapphire not only exhibit ferromagnetism with a Curie temperature close to 650 K, but also a giant magnetic moment of 7.5+/-0.5 micro(B)/Co, not yet reported in any diluted magnetic semiconductor system. The films are semiconducting and optically highly transparent. 相似文献
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Devices which simplify the collection and improve the quality of scattered-light photoelastic data are described. These devices include electromechanically controlled optics for varying the polarization of the incident-light beam and a photometric scanner for observing the scattered-light fringes. 相似文献
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Sato Y Buban JP Mizoguchi T Shibata N Yodogawa M Yamamoto T Ikuhara Y 《Physical review letters》2006,97(10):106802
The role of Pr doping on double Schottky barrier formations at ZnO single grain boundaries was investigated by the combination of current-voltage measurements, atomic-resolution Z-contrast scanning transmission electron microscopy, and first-principles calculations. Although Pr segregated to the specific atomic site along the boundaries, it was found not to be the direct cause of nonlinear current-voltage properties. Instead, under appropriate annealing conditions, Pr enhances formations of acceptor-type native defects that are essential for the creation of double Schottky barriers in ZnO. 相似文献
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G. Duscher J.P. Buban N.D. Browning M.F. Chisholm S.J. Pennycook 《Interface Science》2000,8(2-3):199-208
To understand the electronic properties of doped grain boundaries, we reviewed the atomic scale techniques currently available to study the electronic structure at pristine SrTiO3 grain boundaries. The knowledge gained from the pristine boundaries is used to interpret experimental and theoretical results from a Mn doped 5 SrTiO3 grain boundaries. Mn atoms are shown to preferentially substitute at specific Ti sites at the grain boundary core. Furthermore, the formal oxidation state of the Mn atoms at the grain boundary core was found to be reduced compared to the Mn atoms substituting for Ti in the bulk. This change of valence did not, however, significantly affect the atomic structure of the grain boundary, as determined by Z-contrast imaging and electron energy-loss spectroscopy, which revealed similar fine-structure features at both the doped and pristine grain boundary. We conclude, therefore, that composition and atomic structure have different effects on the local electronic structure and should be treated separately in any segregation and electrical conductivity models for grain boundaries. 相似文献
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