Shot-noise-induced random telegraph noise in shuttle current

Random telegraph noise in the electric current produced by shot noise is predicted for an array of movable colloid particles by Monte Carlo and molecular dynamics calculations. The electron transport is attributed to the shuttle mechanism where moving colloid particles carry charges. The colloid-particle motion induced by the source-drain voltage shows periodic and/or quasiperiodic vibrations, and the current value depends on the vibration modes. Shot noise that is uncorrelated with the colloid-particle motion causes transitions between the periodic and quasiperiodic vibration modes, resulting in random switching between the current levels corresponding to the vibration modes.     

Staphylococcus aureus Penicillin‐Binding Protein 2 Can Use Depsi‐Lipid II Derived from Vancomycin‐Resistant Strains for Cell Wall Synthesis

Vancomycin‐resistant Staphylococcus aureus (S. aureus) (VRSA) uses depsipeptide‐containing modified cell‐wall precursors for the biosynthesis of peptidoglycan. Transglycosylase is responsible for the polymerization of the peptidoglycan, and the penicillin‐binding protein 2 (PBP2) plays a major role in the polymerization among several transglycosylases of wild‐type S. aureus. However, it is unclear whether VRSA processes the depsipeptide‐containing peptidoglycan precursor by using PBP2. Here, we describe the total synthesis of depsi‐lipid I, a cell‐wall precursor of VRSA. By using this chemistry, we prepared a depsi‐lipid II analogue as substrate for a cell‐free transglycosylation system. The reconstituted system revealed that the PBP2 of S. aureus is able to process a depsi‐lipid II intermediate as efficiently as its normal substrate. Moreover, the system was successfully used to demonstrate the difference in the mode of action of the two antibiotics moenomycin and vancomycin.     

Reaction of arylmethanesulfonyl and styrylmethanesulfonyl chlorides with triethylamine

A series of arylmethanesulfonyl chlorides were treated with triethylamine in THF to give stilbenes in excellent yields. Workup of the mixtures below 10 °C permits isolation of stilbene episulfones which on warming decompose to yield the corresponding stilbenes stereospecifically. Application of the reaction to 9-fluorenylsulfonyl chloride affords bifluorenylidene, while trans-styrylmethanesulfonyl chloride gives 4,5-dihydro- 4,5-diphenylthiepin 1,1-dioxide and 1,6-diphenylhexatriene.     

Efficient total synthesis of (+)-negamycin, a potential chemotherapeutic agent for genetic diseases

Herein, we describe an efficient strategy for the total synthesis of (+)-negamycin using commercially available achiral N-Boc-2-aminoacetaldehyde as starting material with 42% overall yield for a limited number of steps.     

Mo-Au combo catalysis for rapid 1,3-rearrangement of propargyl alcohols into alpha,beta-unsaturated carbonyl compounds

The combination of Mo and cationic Au catalysts dramatically accelerated the rearrangement of diverse propargyl alcohols, which includes a short reaction time, mild conditions, and high product yields. A practical application to the highly challenging primary propargyl alcohols and the N-alkynyl amides is achieved.     

Design and synthesis of a novel ring-expanded 4′-thio-apio-nucleoside derivatives

The synthesis of a ring-expanded 4′-thio-apio-nucleoside derivative 4, designed to serve as a potential anti-HIV agent, is described. The epoxy alcohol derivative 10, prepared from 2-butene-1,4-diol, was converted to an allylsulfide derivative 13 in 3 steps. Ring-closing-metathesis of 13 gave the dihydrothiopyran derivative 20, which was further converted into sulphoxide 24. A Pummerer-type thioglycosylation reaction of 24 with a persilylated uracil derivative, followed by conversion to a cytosine derivative and deprotection, gave a racemic mixture of the ring-expanded 4′-thio-apio-nucleoside derivative 4 in good yield.     

Evaluation of gradient-index array alignment

Optical Review - A gradient-index (GRIN) array is used as an imaging unit in light-emitting diode (LED) printers. In this study, we measure tilts of GRINs in an array and analyze the intensity...     

Triacylglycerol/phospholipid molecular species profiling of fatty livers and regenerated non-fatty livers in cystathionine beta-synthase-deficient mice, an animal model for homocysteinemia/homocystinuria

Fatty liver is one of the typical manifestations in homocysteinemia/homocystinuria patients and their genetic animal model, mice lacking cystathionine ??-synthase (Cbs ^?/?). The vast majority of Cbs ^?/? die within 4?weeks after birth via yet unknown mechanisms, whereas a small portion survive to adulthood, escaping fatty degeneration of the liver during lactation periods, through regeneration. To investigate the molecular basis of such fatty changes, we analyzed lipid components in fatty livers of 2-week-old Cbs ^?/? and regenerated non-fatty livers of 8-week-old Cbs ^?/? survivors using a chip-based nanoESI (electrospray ionization)-MS system, which allows quantitative detection of triacylglycerol/phospholipid molecular species. Hepatic levels of all major triacylglycerol species were much higher in Cbs ^?/? than in wild-type mice at 2?weeks, although not at 8?weeks. Levels of some phospholipid species were either up- or downregulated in 2-week-old Cbs ^?/?; e.g. saturated (16:0 and 18:0) or mono-unsaturated (16:1 and 18:1) fatty acids-containing phosphatidylcholine/phosphatidylethanolamine species were upregulated, while poly-unsaturated fatty acids-containing phosphatidylcholine (18:2?C18:2 and 18:2?C20:5), phosphatidylethanolamine (18:1?C20:4), and phosphatidylinositol (18:0?C20:4) were downregulated. Capillary electrophoresis-MS analysis identified high-level accumulation of S-adenosylmethionine and S-adenosylhomocysteine in fatty livers of 2-week-old Cbs ^?/? but much less in non-fatty livers of 8-week-old Cbs ^?/?. Although hepatic S-adenosylmethionine/S-adenosylhomocysteine ratios were comparable between 2-week-old Cbs ^?/? and wild-type, global protein arginine methylation was disturbed in fatty livers of Cbs ^?/?. Our results suggest that cellular signaling mediated by altered phospholipid contents might be involved in pathogenesis of fatty liver in Cbs ^?/?C.     

Growth of gold nanorods in gelled surfactant solutions

Gold nanorods have been actively studied for new nanotechnological materials and industrial applications. It is well known that gold nanorods grow spontaneously in surfactant solutions, and a number of procedures for their preparation have been reported; however, the factors that determine the morphology have not been well understood. In this study, we observed the time series of the growth process of gold nanorods in gelled surfactant solutions by completely stopping the growth reaction. This growth process was compared to that in solution without gelation. The comparison indicates that the self-assembly of surfactant molecules affected the resulting shape, especially the short-axis length, of the nanorods. Small-angle neutron scattering (SANS) experiments revealed that the gelled solutions form lamellar structures, whereas nongelled systems form spherical micelles. On the bases of these results, we present a model showing that the short-axis length of gold nanorods is affected by a decrease in the spontaneous curvature of the outer surfactant layer and/or an increase in the bending modulus of the surfactant membrane neighboring the gold surface.