A Convenient Synthesis of Sphingosine and Ceramide from D-Xylose or D-Galactose

Ceramide, i.e., N-fatty acylated sphingosine and its homolog, is a highly heterogeneous and hydrophobic component of the glycosphingolipids¹ such as gangliosides,² which may play important roles in the surface region of the biological membranes.     

Poly‐ε‐Lysine Modified Nanocarbon Film Electrodes for LPS Detection

We developed an electrochemical system for detecting lipopolysaccharide (LPS) that uses an ultraflat nanocarbon film electrode modified with poly‐ε‐lysine with a high affinity to LPS. LPS was captured on the modified electrode, and then ferrocene labeled polymyxin B (FcPMB) was captured on the LPS adsorbed electrode via the LPS‐PMB affinity interaction. The adsorbed FcPMB provided an amplified response with Fe²⁺ ions, and the current response was dependent on the amount of captured LPS (LOD=2.0 ng/mL). This was due to the efficient accumulation of the obtained current for LPS and the very low noise made possible by the ultraflat surface.     

General Method to Increase Carboxylic Acid Content on Nanodiamonds

Carboxylic acid is a commonly utilized functional group for covalent surface conjugation of carbon nanoparticles that is typically generated by acid oxidation. However, acid oxidation generates additional oxygen containing groups, including epoxides, ketones, aldehydes, lactones, and alcohols. We present a method to specifically enrich the carboxylic acid content on fluorescent nanodiamond (FND) surfaces. Lithium aluminum hydride is used to reduce oxygen containing surface groups to alcohols. The alcohols are then converted to carboxylic acids through a rhodium (II) acetate catalyzed carbene insertion reaction with tert–butyl diazoacetate and subsequent ester cleavage with trifluoroacetic acid. This carboxylic acid enrichment process significantly enhanced nanodiamond homogeneity and improved the efficiency of functionalizing the FND surface. Biotin functionalized fluorescent nanodiamonds were demonstrated to be robust and stable single-molecule fluorescence and optical trapping probes.     

Analysis of the Effects of Protic,Aprotic, and Multi-Component Solvents on the Fluorescence Emission of Naphthalene and its Exciplex with Triethylamine

The emission spectra of naphthalene (NP)–triethylamine (TEA) systems were measured under steady-state illumination conditions in some protic and aprotic solvent-tetrahydrofuran (THF) mixtures. The fluorescence spectrum of the NP–TEA system in THF could be separated into two component bands (band A at 329 nm (fluorescence of NP) and band B at 468 nm (emission from an intermolecular exciplex)). The intensities of bands A and B decreased with increasing solvent polarity. The intensity of band B also decreased owing to the hydrogen-bonding interaction between TEA and protic solvents, but in this case the intensity of band A increased. The decrease in the intensity of band A with increasing solvent polarity is considered to be caused by the enhanced formation of an ion-pair parallel to the formation of an exciplex with increasing solvent polarity. The decrease in the intensity of band B is considered to be caused by the enhanced formation of ion-pair both parallel to and through the formation of the exciplex. The increase in the intensity of band A and the decrease in that of band B upon the addition of protic solvents is caused by the decrease in the concentration of free TEA. Acetonitrile only has a polar effect and trichloroacetic acid only has a hydrogen-bonding (protonation) effect, while alcohols have both the effects.     

First-principles molecular dynamics simulation of biased electrode/solution interface

First-principles molecular dynamics simulations have been carried out for water in contact with Pt(1 1 1) surface. To apply negative bias potential to the water/Pt interface, excess electrons were added to our slab model using the recently developed computational scheme called “effective screening medium (ESM)”. Water molecules located away from the surface reoriented themselves to screen the electric field, but they responded differently near the surface. Water molecules nearest to the surface, forming a distinct layered structure with the hydrogen atom directed to the surface, increased the density with increasing field. On these bases, we discuss microscopic aspects of the electric double layer.     

Analysis of pyridylaminated oligosaccharides using liquid chromatography–mass spectrometry with a monolithic capillary column

We examined the utility of a monolithic capillary column in the analysis of pyridylaminated oligosaccharides. Fluorescence detection and mass spectrometry were used to monitor a series of oligosaccharides. Although the total-ion chromatogram appeared similar to that obtained with fluorescence detection, the sensitivity of this technique was limited, especially in the case of smaller oligosaccharides. This limitation was overcome by applying selected ion current monitoring. Further, the capillary column also exhibited good reproducibility. We showed that the retention times obtained by using the monolithic capillary column could be converted into the standard data to enable comparison of the experimental data with the existing data. Furthermore, our studies revealed an important difference in the separation profile, i.e., the monolithic capillary column could resolve smaller oligosaccharides to a greater extent.     

Structure and properties of ethyl (2-benzimidazolyl)cyanoacetimidate

The revision of the structure of hydrolytic product from 4-cyano-1-ethoxypyrirnido[1,6-a]benzimidazole (1) and the properties of ethyl (2-benzimidazolyl)cyanoacetimidate (3a) are described.     

On component factors

LetK be a connected graph. A spanning subgraphF ofG is called aK-factor if every component ofF is isomorphic toK. On the existence ofK-factors we show the following theorem: LetG andK be connected graphs andp be an integer. Suppose|G| = n|K| and 1 <p < n. Also suppose every induced connected subgraph of orderp|K| has aK-factor. ThenG has aK-factor.     

SUPER TOUGH GELS WITH A DOUBLE NETWORK STRUCTURE

Living tissues work with fantastic functions in soft and wet gel-like state.Thus,hydrogels have attracted much attention as excellent soft and wet materials,suitable tot making artificial organs for medical treatments.However, conventional hydrogels are mechanically too weak for practical uses.We have created double network (DN) hydrogels with extremely high mechanical strength in order to overcome this problem.DN gels are interpenetrating network (IPN) hydrogels consisting of rigid polyelectrolyte and s...