Emergence of Non‐Hexagonal Crystal Packing of Deswollen and Deformed Ultra‐Soft Microgels Under Osmotic Pressure Control

Porins represent a group of channel forming proteins that facilitate diffusion of small solutes across the outer membrane of Gram-negative bacteria, while excluding large molecules (>650 Da). Planar membranes reconstituted from purified matrix porin (OmpF protein) trimers and phospholipids have allowed quantitative functional studies of the voltage-dependent channels and revealed concerted activation of triplets. Under the same reconstitution conditions but using high protein concentrations porin aggregated to 2D lattices suitable for electron microscopy and image processing. Depending on the lipid-to- protein ratio three different crystal packing arrangements were observed: a large (a = 93 Å) and a small (a = 79 Å) hexagonal and a rectangular (a = 79 Å b = 139 Å) form with p3 symmetry for the hexagonal arrays. In all crystal forms distinct stain filled triplet indentations could be seen and were found to be morphologically identical within a resolution of (22 Å). It is tempting to correlate stain triplets with triple channels, but the proof of this hypothesis requires an analysis of the structure in 3 dimensions.

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Origin of the alternate bright/dark contrast in HREM images of hexagonal crystals, particularly 6H-SiC

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010015040x ◽

1993 ◽

Vol 51 ◽

pp. 914-915

Author(s):

J.S. Bow ◽

R.W. Carpenter ◽

M.J. Kim

Keyword(s):

High Resolution ◽

Incident Beam ◽

Hexagonal Crystal ◽

Detailed Explanation ◽

Similar Character ◽

High Resolution Images ◽

The Difference ◽

Zigzag Shape ◽

Hexagonal Crystals ◽

Dark Contrast

A prominent characteristic of high-resolution images of 6H-SiC viewed from [110] is a zigzag shape with a period of 6 layers as shown in Fig.1. Sometimes the contrast is same through the 6 layers of (0006) planes (Fig.1a), but in most cases it appears as in Fig.1b -- alternate bright/dark contrast among every three (0006) planes. Alternate bright/dark contrast is most common for the thicker specimens. The SAD patterns of these two types of image are almost same, and there is no indication that the difference results from compositional ordering. O’Keefe et al. concluded this type of alternate contrast was due to crystal tilt in thick parts of the specimen. However, no detailed explanation was given. Images of similar character from Ti3Al, which is also a hexagonal crystal, were reported by Howe et al. Howe attributed the bright/dark contrast among alternate (0002) Ti3Al planes to phase shifts produced by incident beam tilt.

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The crystallography characteristic of (Mn,Fe)S single crystal

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100177623 ◽

1990 ◽

Vol 48 (4) ◽

pp. 898-899

Author(s):

Jiang Xishan

Keyword(s):

Single Crystal ◽

Cast Steel ◽

Point Group ◽

Central Area ◽

Hexagonal Crystal ◽

Growth Step ◽

Left And Right ◽

Relationship Of ◽

Fcc Structure ◽

New Discovery

This paper reports the growth step pattern and morphology at equilibrium and growth states of (Mn,Fe)S single crystal on the wall of micro-voids in ZG25 cast steel by using scanning electron microscope. Seldom report was presented on the growth morphology and steppattern of (Mn,Fe)S single crystal.Fig.1 shows the front half of the polyhedron of(Mn,Fe)S single crystal,its central area being the square crystal plane,the two pairs of hexagons symmetrically located in the high and low, the left and right with a certain, angle to the square crystal plane.According to the symmetrical relationship of crystal, it was defined that the (Mn,Fe)S single crystal at equilibrium state is tetrakaidecahedron consisted of eight hexagonal crystal planes and six square crystal planes. The macroscopic symmetry elements of the tetrakaidecahedron correpond to Oh—n3m symmetry class of fcc structure,in which the hexagonal crystal planes are the { 111 } crystal planes group,square crystal plaits are the { 100 } crystal planes group. This new discovery of the (Mn,Fe)S single crystal provides a typical example of the point group of Oh—n3m.

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