Ca2+ INFLUX INDUCED BY PHOTODYNAMIC ACTION IN HUMAN CEREBRAL GLIOMA (U-87 MG) CELLS: POSSIBLE INVOLVEMENT OF A CALCIUM CHANNEL

Abstract The plasma membrane has been implicated as a critical target of photodynamic action on cells. We have observed that the photosensitization of human cerebral glioma (U-87 MG) cells by hematoporphyrin derivative (HpD) causes a large increase in intracellular calcium [Ca²⁺]. This increase in [Ca²⁺]_i was solely due to the influx of extracellular Ca²⁺ through the plasma membrane and showed a dependence on HpD concentration, light dose and concentration of calcium in the extracellular medium. The magnitude of the Ca²⁺ influx decreased with increasing postirradiation time, which suggests that the cell membrane partially recovers from the photodynamic injury. The photoinduced Ca²⁺ influx was inhibited by the Ca²⁺ channel blocker diltiazem and the reducing agent dithioerythritol. These findings are discussed in terms of possible activation of a Ca²⁺ channel as a result of photosensitization.     

h-Deformation of GL(1∣1)

An h-deformation of a (graded) Hopf algebra of functions on supergroup GL(11) is introduced via a contraction of GL _q (11). The deformation parameter h is odd (Grassmann). A related differential calculus on h-superplane is presented.     

Duality for a Lorentz quantum group

We give the algebra _q ^/* dual to the matrix Lorentz quantum group _q of Podles-Woronowicz, and Watamuraet al. As a commutation algebra, it has the classical form _q ^/* U _q (sl(2, )) U _q (sl(2, )). However, this splitting is not preserved by the coalgebra structure which we also give. For the derivation, we use a generalization of the approach of Sudbery, viz. tangent vectors at the identity.     

Evidence of interactions in Co-HfO2 granular films

Co-HfO(2) granular films with varying numbers of bilayers were studied by means of transmission electron microscopy (TEM), magnetization loops and zero-field-cooled and field-cooled (ZFC-FC) magnetization. Grain size properties inferred from the measurement techniques were found to be different from those observed from TEM. We show that a modified Langevin function that accounts for dipolar interactions reconciles grain size properties observed by TEM. The mean blocking temperature seen from ZFC-FC analysis was observed to be greater compared to that inferred from TEM data. Moreover, it exhibited a trend with increasing numbers of bilayers. We proposed an explanation for these differences on the basis of the degree of dipolar interactions.     

Resolution of N-protected amino acid esters using whole cells of Candida parapsilosis ATCC 7330

Whole cells of Candida parapsilosis ATCC 7330 were used for the resolution of N-acetyl amino acid esters. Excellent enantioselectivities (E = 40 to >500) were achieved for the resolution of N-protected protein and non-protein amino acid esters giving good yields (28–50%) and high enantiomeric excesses (up to >99%) for both enantiomers.     

Solid-Phase Synthesis of 2,4-diaminopyrimidines via Lewis acid-mediated aromatic nucleophilic substitution

Primary amines were immobilized on (4-formyl-3,5-dimethoxyphenoxy)methylpolystyrene resin via reductive amination. Attachment of two different 4-chloro-2-methylthiopyrimidines, followed by sulfide oxidation, led to their corresponding sulfone intermediates. Aromatic nucleophilic substitution with various anilines or heteroaromatic amines in the presence of trimethyl aluminum afforded the desired 2,4-diaminopyrimidines after acidic cleavage from the resin. The synthetic methodology described herein was validated with the synthesis of a small 162-member library.     

Glycosylidene Carbenes Part 12. A new synthesis and some reactions of spirooxiranes

The diazirine 1 , upon thermolysis or photolysis in either acetone or cyclohexanone, at different concentrations, yield the spiro epoxides 2 and 3 , and 4 and 5 , respectively (Scheme 1). Yield of 2 and 3 depended both on the temperature and the concentration, and correlated inversely with the yield of the major by-product, the enol-derived glycoside 6 . Other by-product were the benzyloxglycal 7 and the lactone azines 8 . ZnCl₂-Promoted methanolysis of 2 under mild condition yielded mixture of the uloside 9 and 10 (1.2:1); similarly, 4 yielded 11 and 12 (1.8:1; Scheme 2). More strongly acidic conditions converted 11 into 12 , evidencing that ZnCl₂-promoted methanolysis proceeds under kinetic control, which is rationalized. The diazirine 13 , upon thermolysis of Photolysis in either acetone of cyclohexanone, yielded the α-D -configurated spiro epoxides 14 and 16 , and the α-D -configurated dihydrooxazoles 15 and 17 , respectively (Scheme 3), which are either formed by ring-opening of ß-D -epoxides, by competitive interception of the initially formed, hypothetical addition products of the intermediate carbene to the ketones. The glycosylidene carbenes, derived from 1 or 13 are not very reactive towards ketones, yields are good only when sterically unhindered ketones are used in large excess.     

Microwave Activated Solid Support Synthesis of New Antibacterial Quinolones

Summary.  A novel synthesis of 6-fluoro-7-(5-aryl-1,3,4-thiadiazol/oxadiazol-2-yl-sulfanyl)-4-quinolone-3-carboxylic acids from 7-chloro-6-fluoro-4-quinolone-3-carboxylic acid and 5-substituted 1,3,4-thiadiazoles/oxadiazoles on basic alumina under microwave activation is described. All compounds were screened for their in vitro antibacterial activity against B. lichenformis, 2689, K. aerogens 2281, S. typhimurium 2501, E. herbicola 2491, and P. vulgaris 2027 and found to possess activities comparable to that of the standard drug norfloxacin. Received May 2, 2000. Accepted (revised) June 13, 2000     

Transient Metallo-Lipidoid Assemblies Amplify Covalent Catalysis of Aqueous and Non-Aqueous Reactions

Dissipative supramolecular assemblies are hallmarks of living systems, contributing to their complex, dynamic structures and emerging functions. Living cells can spatiotemporally control diverse biochemical reactions in membrane compartments and condensates, regulating metabolite levels, signal transduction or remodeling of the cytoskeleton. Herein, we constructed membranous compartments using self-assembly of lipid-like amphiphiles (lipidoid) in aqueous medium. The new double-tailed lipidoid features Cu(II) coordinated with a tetravalent chelator that dictates the binding of two amphiphilic ligands in cis-orientation. Hydrophobic interactions between the lipidoids coupled with intermolecular hydrogen bonding led to a well-defined bilayer vesicle structure. Oil-soluble S_NAr reaction is efficiently upregulated in the hydrophobic cavity, acting as a catalytic crucible. The modular system allows easy incorporation of exposed primary amine groups, which augments the catalysis of retro aldol and C−N bond formation reactions. Moreover, a higher-affinity chelator enables consumption of the Cu(II) template leveraging the differential thermodynamic stability, which allows a controllable lifetime of the vesicular assemblies. Concomitant temporal upregulation of the catalytic reactions could be tuned by the metal ion concentration. This work offers new possibilities for metal ion-mediated dynamic supramolecular systems, opening up a massive repertoire of functionally active dynamic “life-like” materials.