Spontaneous membrane fusion induced by chemical formation of ceramides in a lipid bilayer

Mere chemical generation of ceramide and related double-chain lipids in the membrane of small unilamellar vesicles (SUVs) induces fusion of the vesicles. The lipids can be successfully prepared by dehydrocondensation between single-chain lipids (fatty acids and sphingosine or its analogues) in a lipid bilayer of the SUV by using a combination of 2-chloro-4,6-dimethoxy-1,3,5-triazine and amphiphilic tertiary amine catalysts, a process that can be compared to a successive enzyme model system for a fatty acyl-CoA synthetase followed by acyltransferase. The SUV spontaneously undergoes membrane fusion upon this internal chemical stimulation by the artificial enzyme system.     

Total synthesis of lamellarins D, L, and N

Total synthesis of cytotoxic marine alkaloids, lamellarins D, L, and N, has been achieved by using Hinsberg-type pyrrole synthesis and palladium-catalyzed Suzuki-Miyaura coupling of the 3,4-dihydroxypyrrole bistriflate 6 as the key reactions. The total yields of lamellarins D, L, and N from the common intermediate 6 are 54, 58, and 50%, respectively.     

Chemical component mapping of pulverized toner by scanning transmission X-ray microscopy

Toners are micron scale polymer particles constructed of several kinds of resin, pigment, wax, etc. Transmission electron microscopy (TEM) is used for observation of the dispersion of the component materials in toners, but TEM images cannot identify simultaneously all components. Scanning transmission X-ray microscopy (STXM) not only provides simultaneous observation of spatial distributions of wax, resin and carbon black in toners, but it also provides detailed, quantitative, chemical information about the wax and resin environments through chemical component maps derived from multiple energy image sequences. The capabilities of STXM for toner analysis are illustrated by results of a study of a toner for black/white copy/print applications.     

Formation of the CuII–Phenoxyl Radical by Reaction of O2 with a CuII–Phenolate Complex via the CuI–Phenoxyl Radical

Reaction of Cu(ClO₄)₂ ⋅ 6 H₂O with a tripodal 2N2O ligand, H₂Me₂NL, having a p-(dimethylamino)phenol moiety, in CH₂Cl₂/MeOH (1:1 v/v) under basic conditions under an inert gas atmosphere gave [Cu(Me₂NL)(H₂O)] ( 1 ). The same reaction carried out under aerobic conditions gave [Cu(Me₂NL)(MeOH)]ClO₄ ( 2 ), which could be obtained also from the isolated complex 1 by reaction with O₂ in CH₂Cl₂/MeOH. The X-ray crystal structures of 1 and 2 revealed similar square-pyramidal structures, but 2 showed the (dimethylamino)phenoxyl radical features. Complex 1 exhibits characteristic Cu^II EPR signals of the d ground state in CH₂Cl₂/MeOH at 77 K, whereas 2 is EPR-silent. The EPR and X-ray absorption fine structure (XAFS) results suggest that 2 is assigned to the Cu^II–(dimethylamino)phenoxyl radical. However, complex 1 showed different features in the absence of MeOH. The EPR spectrum of the CH₂Cl₂ solution of 1 exhibits distortion from the d ground state and a temperature-dependent equilibrium between the Cu^II–(dimethylamino)phenolate and the Cu^I–(dimethylamino)phenoxyl radical. From these results, Cu^II–phenoxyl radical complex 2 is concluded to be formed by the reaction of 1 with O₂ via the Cu^I–phenoxyl radical species.     

Second Harmonic Generation Measurements for Biomacromolecules: Celluloses

The molecular chain orientation of mercerized cellulose II was examined by optical second harmonic generation (SHG) measurements. The SHG intensities of several kinds of mercerized cellulose II were found to be much larger than those expected for a structural model with an antiparallel molecular chain orientation as proposed by X-ray studies. This result suggests that the orientation of mercerized cellulose II is parallel as suggested by molecular dynamics simulation. © 2004 The Optical Society of Japan