Simultaneous measurements of K+ and calcein release from liposomes and the determination of pore size formed in a membrane.

The changes induced by biologically active substances in the permeability to K+ and calcein of liposomes composed of egg phosphatidylcholine and cholesterol were measured simultaneously in order to rapidly screen the sizes of pores formed in a membrane, using different sized markers. The substances examined in the present study were classified into three types based on differences in the rates at which K+ and calcein were released. The first type released only K+, and included gramicidin A. The second type predominantly released K+, preceding the release of calcein, and included amphotericin B and nystatin. The third type, including antimicrobial peptides, such as gramicidin S, alamethicin, and melittin, and several membrane-active drugs, like celecoxib (non-steroidal anti-inflammatory drug), 1-dodecylazacycloheptan-2-one (named azone; skin permeation enhancer), and chlorpromazine (tranquilizer), caused the release of K+ and calcein simultaneously. Thus, the sizes of pores formed in a liposomal membrane increased in the following order: types one, two, and three. We determined the size more precisely by conducting an osmotic protection experiment, measuring the release of calcein in the presence of osmotic protectants of different sizes. The radii of pores formed by the second type, amphotericin B and nystatin, were 0.36 - 0.46 nm, while the radii of pores formed by the third type were much larger, 0.63 - 0.67 nm or more. The permeability changes induced by substances of the third type are discussed in connection with a transient pore formed in a lipid packing mismatch taking place during the phase transition of dipalmitoylphosphatidylcholine liposomes.     

Synthesis of heterocyclic compounds via nucleophilic aroylation catalyzed by imidazolidenyl carbene

Xanthones and acridones were synthesized from 3,4-difluoronitrobenzene and 2-fluorobenzaldehydes in two or three steps. The key step was nucleophilic aroylation catalyzed by imidazolidenyl carbene. The nucleophilic aroylation of 3,4-difluoronitrobenzene afforded 2,2'-difluoro-4-nitrobenzophenones. The cyclization of the difluorobenzophenones with O-nucleophile and N-nucleophile yielded 3-nitroxanthones and 3-nitroacridones, respectively. Indazole, quinolino[2,3-b]quinoxaline, and thianaphtho[2,3-b]quinoxaline derivatives were also synthesized via nucleophilic aroylation of 2,3-dichloroquinoxaline followed by cyclization with nucleophiles.     

Quantitative analysis of long-range interactions between adsorbed dipolar molecules on Cu(111)

Highly dispersed superstructures of a dipolar iridium complex are formed on a Cu(111) surface. We show that the dilute superstructures with density-controlled intermolecular separations are stabilized by the strong and long-range repulsive intermolecular interactions. The repulsive intermolecular interactions are quantitatively evaluated by using low-temperature scanning tunneling microscopy, which are characterized by the surface-enhanced dipole-dipole interactions.     

Simulated reflectance spectra and point spread functions in database constructed by moderate grouping of nine layers in skin model

Optical Review - This paper presents a numerical study on simulated spectra and point spread functions in the database that we constructed by moderate grouping of nine layers in a skin model. The...     

Construction of positively-charged layered assemblies assisted by cyclodextrin complexation

A beta-cyclodextrin dimer is found to be effective in preparing a layer-by-layer architecture of positively charged ferrocene-appended poly(allylamine) presumably on the basis of strong beta-cyclodextrin-ferrocene host-guest interaction.     

Dissipative and Autonomous Square‐Wave Self‐Oscillation of a Macroscopic Hybrid Self‐Assembly under Continuous Light Irradiation

Building a bottom‐up supramolecular system to perform continuously autonomous motions will pave the way for the next generation of biomimetic mechanical systems. In biological systems, hierarchical molecular synchronization underlies the generation of spatio‐temporal patterns with dissipative structures. However, it remains difficult to build such self‐organized working objects via artificial techniques. Herein, we show the first example of a square‐wave limit‐cycle self‐oscillatory motion of a noncovalent assembly of oleic acid and an azobenzene derivative. The assembly steadily flips under continuous blue‐light irradiation. Mechanical self‐oscillation is established by successively alternating photoisomerization processes and multi‐stable phase transitions. These results offer a fundamental strategy for creating a supramolecular motor that works progressively under the operation of molecule‐based machines.     

Mild and efficient pentafluorophenylammonium triflate (PFPAT)-catalyzed C-acylations of enol silyl ethers or ketene silyl (Thio)acetals with acid chlorides

A pentafluorophenylammonium triflate (PFPAT) catalyst (5 mol %) successfully promoted C-acylation of enol silyl ethers with acid chloride to produce various beta-diketones (12 examples; 62-92% yield). Similarly, C-acylation of ketene silyl acetals or ketene silyl thioacetals (i.e., crossed Claisen condensation) proceeded smoothly to provide not only alpha-monoalkylated beta-keto (thio)esters but also thermodynamically unfavorable (less accessible) alpha,alpha-dialkylated beta-keto (thio)esters in good to excellent yield (38 examples; 60-92% yield).     

Combination of glow-discharge and arc plasmas for CF4 abatement

Decomposition of CF₄ by glow-discharge and arc plasmas was studied using a tubular quartz reactor, a disk type, and a T-type quartz reactor. The effects of different metal electrodes, input voltage, and reactor type on the efficiency of CF₄ total destruction (DRE) were studied. The T-shape reactor was more efficient in CF₄ destruction than either the disk or tubular type due to a combined effect of glow discharge and arc plasmas. Several hydrogen and oxygen sources, such as H₂O, H₂, O₂, and CH₄, were used to convert CF₄. Using H₂ and O₂ as the hydrogen and oxygen sources presented better DRE than using H₂O. The effect of different hydrogen and oxygen sources on the conversion of CF₄ followed the trend: (H₂ + O₂) > (CH₄ + O₂) > H₂O. The maximum DRE of 95% was observed with 0.5% CF₄ using H₂ and O₂. A mass spectrometer and an emission spectroscope equipped with a charge-coupled detector (CCD) were used to characterize the products and intermediates. Mass spectrometric studies indicated that the reaction products were HF, CO₂, and trace amounts of NO. N₂ first negative and second positive emission lines were observed in the glow discharge plasmas as well as in the arc plasmas of N₂. However, C and F intermediates were observed only in arc plasmas of CF₄. Reactions occurring in the glow discharge plasmas and arcs seem to follow different mechanisms.     

A new algorithm for a multi-item periodic review inventory system

In this paper, we deal with a multi-item, stochastic, periodic review inventory system with general cost structure which permits partial or complete backlogging of unfilled demand. Since both the (, S) policy and the mixed reorder policy are not optimal, we derive several properties of an optimal ordering policy and propose a new algorithm for computing it. This algorithm is based on the policy iteration method (PIM), but reduces substantially computation times in the policy evaluation and improvement routines of the PIM.