How is it possible to obtain buried interface information through very thick films using a hard-X-ray PEEM?

We analyze the excitation of secondary electrons by hard-X-rays in subsurface layers. By studying core-excited photoelectron lines and their plasmon satellites in photoemission spectra, we show how electrons excited by hard-X-rays can carry information from deep regions deep within the sample to the surface. It is believed that the decay of high-energy photoelectrons via plasmon-loss is strongly related to the production of secondary electrons. For high-energy electrons, however, the momentum transfer to plasmons is small compared to the electron’s initial momentum, so the lateral position on the surface from which the secondary electrons are emitted is close to that of the atom initially excited by the hard-X-rays. This explains why the spatial resolution of hard-X-ray photoelectron emission microscope (HX-PEEM) images is good even if the buried interface is covered by a film with a thickness many times the inelastic mean free path of the primary electrons. This argument explains well recent HX-PEEM results.     

Surface acetylation of bacterial cellulose

Bacterial cellulose was partially acetylated by the fibrous acetylationmethod to modify its physical properties, while preserving the microfibrillarmorphology. The overall degree of substitution was varied from 0.04 to 2.77 bychanging the amount of acetic anhydride added. X-ray diffraction of thepartially acetylated samples showed the crystalline pattern of unmodified celluloseI up to moderate degrees of acetylation, and the change in peak widthsindicatedthat acetylation proceeded from the surface of microfibrils, leaving the coreportion unreacted. Scanning electron microscopy revealed that even low levelsofacetylation were effective to maintain the original microfibrillar morphologyofbacterial cellulose on direct drying from water.     

Charge transfer in duplex DNA containing mismatch

A theory for charge transfer between the electrode and the donor/acceptor molecule coupled through a DNA bridge in solution is developed. We explore the crossover between the coherent tunneling and the incoherent sequential transfer regimes by varying the electrode potential and discuss the effects of single-base mismatches in DNA duplex in both regimes. In the former regime a single-base mismatch in DNA duplex causes a reduction in the charge transfer rate simply by decreasing the electron tunneling matrix element, however, in the latter regime the effects are rather complicated.     

Microvasculature of the olfactory organ in the Japanese monkey (Macaca fuscata fuscata).

Olfaction is an important and primitive sense. As its importance has changed with evolution, anatomic adjustments have occurred in its structure and vasculature. Primates are a family of vertebrates that have had to develop their visual system to adapt to the arboreal environment and have evolved from a macrosmatic to a microsmatic species as the optic system has enlarged. This has resulted in anatomic changes of a small but critical area at the base of the brain. This paper describes the three-dimensional vascular anatomy of the olfactory organ of the Japanese monkey (Macaca fuscata fuscata). This is best understood by dividing the organ into three parts: the olfactory tract, olfactory bulb, and olfactory nerves in the nasal mucosa. The bulb can be partitioned into an outer or cortical part and inner or medullary part. The vasculature and tissue were examined grossly and with light microscopy and scanning electron microscopy of vascular corrosion casts. The olfactory tract and bulb were supplied by an arteriole from the anterior cerebral artery on each side. The tract was supplied by capillaries running spirally with a coarse network. At the olfactory bulb, the arteriole ramified into the intracortical and medullary branches that formed capillary networks. The bulbar intracortical capillaries were divided into two layers with different densities and vascular patterns. The capillaries of the superficial layer had a ladder-like pattern. The branches that ran into the medulla of the olfactory bulb were more widely spaced. Twigs from the posterior ethmoidal artery ran along the nerve fiber and formed intra- and extrafascicular networks. Each region of the olfactory organ had characteristic three-dimensional vascular patterns that were related to their cellular architecture.     

Automated recognition of common geometrical patterns among a variety of three-dimensional moleculars structures

A computer program, COMPASS, is described for searches for common geometrical pattern among a set of chemical compounds. The approach is based on a distance geometry method. The program allows the user to specify some search conditions which are defined with weighting atoms of different types and distance allowance. Information of charges on each atom in molecules can also be included. Examples are presented to illustrate the abilities of the program in relation to structure/activity problems.     

Self-assembly of gold nanorods induced by intermolecular interactions of surface-anchored lipids

Surface-modified gold nanorods (Au NRs) with 1,2-dipalmitoyl- sn-glycero-3-phosphothioethanol (DPPTE) were synthesized, and their self-assembled structures on a silicon substrate were observed using a scanning electron microscope (SEM). The Au NR-DPPTE complex formed characteristic one- and two-dimensional self-assemblies induced by intermolecular interactions of surface-anchored lipids via simple drying process. The interparticle distance between neighboring NRs was uniform at around 5.0 nm, which was consistent with the thickness of the lipid bilayer. Furthermore, we observed the anisotropic configurations of the NR complex, preferentially oriented in a lateral or perpendicular fashion, in a two-dimensional assembled structure dependent on the interfacial hydrophilicity or hydrophobicity of the silicon surface.     

Novel "lipid-flow chip" configuration to determine donor-to-acceptor ratio-dependent fluorescence resonance energy transfer efficiency

We report on the determination of fluorescence resonance energy transfer (FRET) efficiency, which is dependent on the donor-to-acceptor (D-A) ratio, by using a new type of microchannel device called a "lipid-flow chip". The chip comprises two supported lipid bilayers (SLBs) that self-spread from either side of 10 microm wide straight lines and carry molecules embedded in them. We first show that the diffusion process that occurs when the two SLBs collide with each other in the channel and form a unified SLB can be expressed by a one-dimensional diffusion equation. Next we describe a method for determining the FRET efficiency between NBD (donor) and Texas Red (acceptor) from observations using the lipid-flow chip by employing a one-dimensional diffusion model. The advantages of our method are that all the D-A ratios are achieved in one chip, and a large number of data are recorded in one chip. The FRET efficiency varies depending on the D-A ratio under conditions whereby the concentration of the sum of the donors and acceptors is constant. The F?rster radius is also estimated from our results using a known model describing two-dimensional FRET systems, which yields a radius consistent with the previously reported value for NBD and Texas Red.     

Facile fabrication of silver nanofin array via electroless plating

The fabrication of metallic nanostructures is one of the main issues in nanotechnology. This article describes the fabrication of a silver nanofin array by combining microlithography, electroless plating, and an etching technique. Fabricated Ag nanofins have a high aspect ratio (height/width = 10, width = 60 nm, height = 600 nm), and their widths and heights can be controlled by the period of electroless plating and the height of the original line pattern. An isolated Ag nanofin was proven to show metallic electrical conductivity. The current process provides a rapid and shape-designable fabrication method of metallic nanostructures.     

Solid-state NMR analysis of the orientation and dynamics of epigallocatechin gallate, a green tea polyphenol, incorporated into lipid bilayers

Catechins are the principle polyphenolic compounds in green tea; the four major compounds identified are epicatechin (EC), epigallocatechin (EGC), epicatechin gallate (ECg) and epigallocatechin gallate (EGCg). Tea catechins tend to attach externally to their targets, such as viral envelopes, cell membranes, or the surface of low-density lipoproteins. In order to further our understanding of the molecular mobility of these compounds in cells, we examined the interaction of tea catechins with lipid membranes using solid-state NMR techniques. Our previous work indicated that the EGCg molecule is incorporated into lipid bilayers in a unique orientation. However, the detailed configuration, orientation, and dynamics of EGCg in lipid bilayers have not been well-characterized. Here, we investigated the orientation and dynamics of EGCg incorporated into multi-lamellar vesicles (MLVs) and bicelles using solid-state NMR spectroscopy.