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.     

Levels in 74Se, 78, 80Kr and 84Sr and systematics of quasi-γ bands

Quasi-band structures in ⁷⁴Se, ^{78, 80}Kr and ⁸⁴Sr have been investigated using (p, 2nγ) reactions. The members of the quasi-γ band have been observed up to 5⁺ in ⁷⁴Se, ^{78, 80}Kr and up to 3⁺ in⁸⁴Sr. The analyses of the energy systematics of the quasi-γ bands studied in this mass region as well as in other regions make clear the evolution of the quasi-γ band to the γ-band in well-deformed nuclei. In addition to these positive-parity bands, negative-parity levels were observed in ⁷⁴Se, ⁸⁰Kr and ⁸⁴Sr.     

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.     

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.     

Water-mediated interactions in the CRP–cAMP–DNA complex: Does water mediate sequence-specific binding at the DNA primary-kink site?

The cyclic AMP receptor protein (CRP) of Escherichia coli binds preferentially to DNA sequences possessing a T:A base pair at position 6 (at which the DNA becomes kinked), but with which it does not form any direct interactions. It has been proposed that indirect readout is involved in CRP-DNA binding, in which specificity for this base pair is primarily related to sequence effects on the energetic susceptibility of the DNA to kink formation. In the current study, the possibility of contributions to indirect readout by water-mediated hydrogen bonding of CRP with the T:A base pair was investigated. A 1.0 ns molecular dynamics simulation of the CRP-cAMP-DNA complex in explicit solvent was performed, and assessed for water-mediated CRP-DNA hydrogen bonds; results were compared to several X-ray crystal structures of comparable complexes. While several water-mediated CRP-DNA hydrogen bonds were identified, none of these involved the T:A base pair at position 6. Therefore, the sequence specificity for this base pair is not likely enhanced by water-mediated hydrogen bonding with the CRP.     

Synthesis and Characterization of the Orthorhombic Sn3O4 Polymorph

An unexplored tin oxide crystal phase (Sn₃O₄) was experimentally synthesized via a facile hydrothermal method. After tuning the often-neglected parameters for the hydrothermal synthesis, namely the degree of filling of the precursor solution and the gas composition in the reactor head space, an unreported X-ray diffraction pattern was discovered. Through various characterization studies, such as Rietveld analysis, energy dispersive X-ray spectroscopy, and first-principles calculations, this novel material was characterized as orthorhombic mixed-valence tin oxide with the composition Sn^II₂Sn^IVO₄. This orthorhombic tin oxide is a new polymorph of Sn₃O₄, which differs from the reported conventional monoclinic structure. Computational and experimental analyses showed that orthorhombic Sn₃O₄ has a smaller band gap (2.0 eV), enabling greater absorption of visible light. This study is expected to improve the accuracy of hydrothermal synthesis and aid the discovery of new oxide materials.