High-resolution Field-emission Scanning Electron Microscopy Research Articles

High-resolution field-emission scanning electron microscopy of nuclear pore complex.

The nuclear pore complex (NPC) is a large macromolecular assembly inserted into the nuclear envelope (NE). It controls the traffic of proteins, RNA, and RNA proteins between nucleus and cytoplasm. It chemical composition and function are now intensively investigated in many organisms. To understand this unique membrane transport system, we must know the supramolecular organization of the NPC. In recent years, high-resolution field-emission scanning electron microscopy has made important contributions to our knowledge of NPC structure. It provided the first images of the complex and beautiful fish trap-like structure of its intranuclear surface, documented in this review. It also has provided the first images of a new intranuclear structure, a system of branching hollow cables connecting the nuclear interior with the NPCs at the nuclear surface. Most likely this is an intranuclear transport system, assuring efficient exchange between the nuclear interior and the NE, especially in large nuclei.

The measurement of thin-film reaction layers with high-resolution FESEM

Thin-film reactions in ceramic systems are of increasing importance as materials such as oxide superconductors and ferroelectrics are applied in thin-film form. In fact, reactions have been found to occur during the growth of YBa2Cu3O6+x on ZrO2. Additionally, thin-film reactions have also been intentionally initiated for the production of buffer layers for the subsequent growth of high-Tc superconductor thin films. The problem is that the kinetics of ceramic thin-film reactions are not well understood when the reaction layer is very thin; that is, when the rate-limiting step is a phase-boundary reaction as opposed to diffusion of the reactants through the product layer. In this case, the reaction layer is likely to be laterally non-uniform. In the present study, the measurement of thin reaction-product layers is accomplished by first digitally acquiring backscattered-electron images in a high-resolution field-emission scanning electron microscope (FESEM) followed by image analysis. Furthermore, the problem of measuring such small thicknesses (e.g., 20-500nm) over lengths of interfaces longer than 3mm is addressed.

Scanning electron microscopy of type I collagen at the dentin-enamel junction of human teeth.

The dentin-enamel junction constitutes a unique boundary between two highly mineralized tissues with very different matrix composition and physical properties. The nature of the boundary between the ectoderm-derived enamel and mesoderm-derived dentin is not known. This study was undertaken to identify the presence, type, and distribution of collagen at the dentin-enamel junction as an initial step in understanding its structural-functional role in dental occlusion. Sections of human teeth were demineralized with 0.1 M neutral EDTA and examined by high-resolution field-emission scanning electron microscopy at low accelerating voltage. Enamel and dentin were observed to be linked by many parallel 80-120-nm diameter fibrils, which were inserted directly into the enamel mineral and also merged with the interwoven fibrillar network of the dentin matrix. Immunogold labeling for collagen was visualized by secondary electron imaging and backscatter electron imaging at low accelerating voltage. The collagen fibrils at the junctional zone as well as in the dentin matrix were identified as Type I collagen. Collagenase digestion led to loss of the fibrillar structures and prevented immunogold labeling with antibody specific to Type I collagen. Consequently, the dentin-enamel junction can be regarded as a fibril-reinforced bond which is mineralized to a moderate degree.

Size Dependence of Morphology of Diamond Surfaces Prepared by DC Arc Plasma Jet Chemical Vapor Deposition

The size dependence of the surface morphology of a diamond crystal prepared by the dc arc plasma jet chemical vapor deposition (CVD) is observed using a high-resolution field-emission scanning electron microscope (FE-SEM). The difference in the change of the surface morphology between the {111} surface and the {100} surface is caused by the difference in the growth mode; the {111} surface is formed by the multi-nucleation growth mode, whereas the {100} surface is formed by the single nucleation growth mode.