Untersuchung von Fetten und Oelen

Ohne Zusammenfassung     

SV40 INDUCTION FROM A MAMMALIAN CELL LINE BY ULTRAVIOLET RADIATION and THE PHOTOSENSITIZERS 8-METHOXYPSORALEN and ANGELICIN

Abstract SV40-transformed weanling Syrian hamster kidney cells were exposed to long wavelength ultraviolet radiation in the presence of 8-methoxypsoralen or angelicin. The number of viruses induced as a result of this treatment was quantitated on CV-1P cells. The results indicate that angelicin, which is generally believed to form only monoadducts, is a potent viral inducing agent even when compared with 8-methoxypsoralen (8-MOP), which forms both monoadducts and crosslinks. At low radiation exposures 8-MOP is more effective than angelicin; as the radiation exposure is increased angelicin is capable of inducing the same peak level of virus expression as was 8-MOP. It appears that the induction of SV40 is a phenomenon possibly related to the repair of monoadducts.     

A Heterogeneous‐Catalyst‐Based,Microwave‐Assisted Protocol for the Synthesis of 2,2′‐Bipyridines

A new method of preparing 2,2′‐bipyridines with short reaction times by using microwave assistance and heterogeneous catalysts has been developed. With a Negishi‐like protocol, it was found that Ni/Al₂O₃–SiO₂ afforded 2,2′‐bipyridine products in up to 86 % yield in 1 h. Palladium supported on alumina also provided yields of 2,2′‐bipyridines comparable to those seen for homogeneous PEPPSI^TM (1,3‐diisopropylimidazol‐2‐ylidene)(3‐chloropyridyl)palladium(II)dichloride) and tetrakis(triphenylphosphanyl)palladium complexes.     

Nanofibril self-assembly of an arylene ethynylene macrocycle

Nanofibril structures have been fabricated from an arylene ethynylene macrocycle (AEM), which consists of a square frame corner-joined by four carbazole moieties. The fabrication was performed through a gelating process by cooling a warm, homogeneous solution in cyclohexane at high temperature (e.g., 100 degrees C) to room temperature. During the gelation, the molecules become organized, with optimal pi-pi stacking in cooperation with the side-chain association. The favorable pi-pi stacking facilitates the 1D growth of molecular assembly.     

Microwave-assisted synthesis of 3,6-di(pyridin-2-yl)pyridazines: unexpected ketone and aldehyde cycloadditions

3,6-Di(pyridin-2-yl)pyridazines are an interesting class of compounds because of their metal-coordinating ability resulting in the self-assembly into [2x2] gridlike metal complexes with copper(I) or silver(I) ions. These and other substituted pyridazines can be prepared by the inverse-electron-demand Diels-Alder reactions between acetylenes and 1,2,4,5-tetrazines. In this contribution, the effect of (superheated) microwave conditions on these generally slow cycloadditions is described. The cycloaddition of acetylenes to 3,6-di(pyridin-2-yl)-1,2,4,5-tetrazine could be accelerated from several days reflux in toluene or N,N-dimethylformamide to several hours in dichloromethane at 150 degrees C. In addition, the unexpected cycloaddition of the enol tautomers of various ketones and aldehydes to 3,6-di(pyridin-2-yl)-1,2,4,5-tetrazine is described in detail providing an alternative route for the synthesis of (substituted) pyridazines.     

Kinetics of membrane raft formation: fatty acid domains in stratum corneum lipid models

The major barrier to permeability in skin resides in the outermost layer of the epidermis, the stratum corneum (SC). The major SC lipid components are ceramides, free fatty acids, and cholesterol. Ternary mixtures containing these constituents are widely used for physicochemical characterization of the barrier. Prior X-ray diffraction and IR spectroscopy studies have revealed the existence of ordered lipid chains packed in orthorhombic subcells. To monitor the kinetics of formation of regions rich in fatty acids, the current study utilizes a modification of the method (J. Phys. Chem. 1992, 96, 10008) developed to monitor component demixing in n-alkane mixtures. The approach is based on changes in the scissoring or rocking mode contours in the IR spectra of (orthorhombically packed) ordered chains. In the current study, equimolar mixtures of ceramides (either non-hydroxy fatty acid sphingosine ceramide or alpha-hydroxy fatty acid sphingosine ceramide) with chain perdeuterated fatty acids (either palmitic or stearic acid) and cholesterol reveal a time evolution of the scissoring contour of the deuterated fatty acid chains following quenching from relatively high temperatures where random mixing occurs. Segregation of domains enriched in the fatty acid component is observed. The kinetics of segregation are sensitive to the quenching temperature and to the chemical composition of the mixture. The kinetic regimes are conveniently catalogued with a power law of the form P=Ktalpha where P is a (measured) property related to domain composition. The time scales for demixing in these experiments are similar to times observed in several studies that have tracked the restoration of the in vivo permeability barrier following nonthermal challenges to SC integrity. Further evidence for the physiological importance of the current measurements is the detection of these phases in native SC. The current work constitutes the first direct, structure-based determination of the kinetics of barrier formation in relevant skin lipid barrier models.     

Practical Study into Enhancing IgG Immobilisation on Screen-Printed Electrodes for Environmental Applications

This work is focused on the influence of pH and applied potential for the immobilisation of rabbit IgG on a carbon screen-printed electrode. The orientation of IgG molecule at the surface is fundamental for activity and reproducibility of the immunosensor. As the electrode potential is increased a particular order may be brought to the immobilised antibodies, i.e. the antibodies adapt a more favourable arrangement on the surface to facilitate better binding. The response increased when changing the pH from basic to acidic medium and the reverse trend was observed for the limit of detection (LOD). When a potential was applied to the electrode, the response generally decreased and the LOD increased in the order acidic > basic > neutral pH. The LODs obtained from antibodies immobilised at acidic pH and + 100 mV were better than the LODs obtained at other conditions.     

Oxidative decarbonylation of m-terphenyl isocyanide complexes of molybdenum and tungsten: precursors to low-coordinate isocyanide complexes

Synthetic studies are presented addressing the oxidative decarbonylation of molybdenum and tungsten complexes supported by the encumbering m-terphenyl isocyanide ligand CNAr(Dipp2) (Ar(Dipp2) = 2,6-(2,6-(i-Pr)(2)C(6)H(3))(2)C(6)H(3)). These studies represent an effort to access halide or pseudohalide M/CNAr(Dipp2) species (M = Mo, W) for use as precursors to low-coordinate, low-valent group 6 isocyanide complexes. The synthesis and structural chemistry of the tetra- and tricarbonyl tungsten complexes trans-W(CO)(4)(CNAr(Dipp2))(2) and trans-W(NCMe)(CO)(3)(CNAr(Dipp2))(2) are reported. The acetonitrile adducts trans-M(NCMe)(CO)(3)(CNAr(Dipp2))(2) (M = Mo, W) react with I(2) to form divalent, diiodide complexes in which the extent of decarbonylation differs between Mo and W. In the molybdenum example, the diiodide, dicarbonyl complex MoI(2)(CO)(2)(CNAr(Dipp2))(2) is generated, which has an S = 1 ground state in solution. Paramagnetic group 6 MX(2)L(4) complexes are rare, and the structure of MoI(2)(CO)(2)(CNAr(Dipp2))(2) is discussed in relation to other diamagnetic and C(2v)-distorted MX(2)L(4) complexes. Diiodide MoI(2)(CO)(2)(CNAr(Dipp2))(2) reacts further with I(2) to effect complete decarbonylation, producing the paramagnetic tetraiodide complex trans-MoI(4)(CNAr(Dipp2))(2). The reactivity of the trans-M(NCMe)(CO)(3)(CNAr(Dipp2))(2) (M = Mo, W) complexes toward benzoyl peroxide is also surveyed, and it is shown that dicarboxylate complexes can be obtained by oxidative or salt-elimination routes. The reduction behavior of the tetraiodide complex trans-MoI(4)(CNAr(Dipp2))(2) toward Mg metal and sodium amalgam is studied. In benzene solution under N(2), trans-MoI(4)(CNAr(Dipp2))(2) is reduced by Na/Hg to the η(6)-arene-dinitrogen complex, (η(6)-C(6)H(6))Mo(N(2))(CNAr(Dipp2))(2). The diiodide-η(6)-benzene complex (η(6)-C(6)H(6))MoI(2)(CNAr(Dipp2))(2) is an isolable intermediate in this reduction reaction, and its formation and structure are discussed in context of putative low-coordinate, low-valent molybdenum isocyanide complexes.