Brominaed β-carbolines from the marine hydroid linnaeus

Three new brotminated β-carbolines (1–3) have been isolated from the lipophylic extract of the marine hydroid Linnaeus and their structures determined on the basis of spectral data including two dimensional proton-carbon shift correlation (direct and long range) NMR spectroscopy. The syntheses of compounds 1–3, starting from the appropriate brominated tryptophan derivatives, are also described.     

A versatile, non-biomimetic route to the preussomerins: syntheses of (+/-)-preussomerins F, K and L

The first total syntheses of the title fungal metabolites preussomerins F, K and L are described and their structures confirmed thereby. The syntheses were achieved following a versatile, unified, non-biomimetic approach, which is easily extendable to prepare other known and novel members of this family. Key steps include the functionalisation of a 2-arylacetal anion, tandem one-pot Friedel-Crafts cyclisation-deprotection, regioselective substrate-directable hydrogenation and reductive-opening of epoxides.     

Gerbes over Orbifolds and Twisted K-Theory

In this paper we construct an explicit geometric model for the group of gerbes over an orbifold X. We show how from its curvature we can obtain its characteristic class in H³(X) via Chern-Weil theory. For an arbitrary gerbe , a twisting K_orb(X) of the orbifold K-theory of X is constructed, and shown to generalize previous twisting by Rosenberg [28], Witten [35], Atiyah-Segal [2] and Bowknegt et. al. [4] in the smooth case and by Adem-Ruan [1] for discrete torsion on an orbifold.The first author was partially supported by the National Science Foundation and Conacyt-México     

On the parameter dependence of the real cubic surfaces in arnold’s form

We consider the topological classification of cubic surfaces which are obtained as intersection of the sphere with the algebraic variety defined by the zeroes of a homogeneous cubic polynomial in Arnold’s normal form. This classification is based on the parameters appearing in this normal form, obtaining a correspondence between the parameters of the surface and its topological type. General classifications of cubic surfaces are made in the projective space ℙ³(ℝ), but our method, based on a very simple combinatorial procedure is easier to implement in . We split the cubic surfaces parameter space into ten equivalence classes.     

Creating molecular diversity from antioxidants in Brazilian propolis. Combination of TOPS-MODE QSAR and virtual structure generation

A QSAR model for antioxidative activity based on the Sub-Structural Molecular Design (TOPS-MODE) approach is developed for a series of compounds present in Brazilian propolis. This approach permitted the structural interpretation of the antioxidative activity of these compounds in terms of bond contributions. By these means we have identified the structural groups and regions that contribute to the antioxidative activity of the cinnamic acid and flavonoid derivatives present in the propolis. These results were then used to identify the positions and substituents to be used in a virtual compound generation experiment. Using this approach a total of 327 compounds were generated from which more than 70 are predicted to be more active than the most powerful antioxidants in the Brazilian propolis. From these 70 compounds less than 20 have been reported in the literature. Consequently, a high proportion of novel compounds with potential antioxidative activity has been identified by the current approach. This contributes to enhance the molecular diversity of the analogues of Brazilian propolis compounds with antioxidative properties.     

Therapeutic drug monitoring for sirolimus in whole blood of organ transplants by high-performance liquid chromatography with ultraviolet detection

We developed and validated an accurate, sensitive, precise and rapid HPLC method with UV detection for the determination of sirolimus in blood samples from renal, cardiac and hepatic transplants. This method overcomes most of the problems related to previously published assays using a narrow-bore column with base deactivated C18 reversed phase. Whole blood samples were purified by a combination of a precipitating blood matrix with zinc sulphate and a single step liquid-liquid extraction with acetone and 1-chlorobutane. Calibration curves (range 2.5-150 ng/ml), were linear with coefficients of correlation better than 0.996. The relative standard deviation was determined to be less than 8%. The present method has also been validated by a reference laboratory (St. George's Hospital Medical School, London, UK). More of 300 clinical samples have been analysed with this method.     

A graphical tool for the prediction of vicinal proton-proton 3J(HH) coupling constants

The easy to use and free available graphical tool MestRe-J, developed for Win-32 platforms, calculates the vicinal proton-proton coupling constants 3J(HH) from the torsion angle phi between the coupled protons for the two kinds of generalized Karplus equations developed by Altona's group as well as for equations from other authors. Besides the classical Haasnoot-de Leeuw-Altona equations, including individual substituent effects that depend on their relative Huggins's electronegativities Deltachi, the program incorporates the more recent and precise Díez-Altona-Donders equations. The substituent effects in these equations, that include effects of interactions between substituents, depend on substituent parameters lambda optimized from the 3J(HH) couplings to methyl groups. Weighted time-averaged couplings can be calculated. The equations for 3J(HH) can be solved to provide the torsion angles phi.     

Saari's conjecture for the collinear -body problem

In 1970 Don Saari conjectured that the only solutions of the Newtonian -body problem that have constant moment of inertia are the relative equilibria. We prove this conjecture in the collinear case for any potential that involves only the mutual distances. Furthermore, in the case of homogeneous potentials, we show that the only collinear and non-zero angular momentum solutions are homographic motions with central configurations.

     

A new implementation of Yen’s ranking loopless paths algorithm

Yens algorithm is a classical algorithm for ranking the K shortest loopless paths between a pair of nodes in a network. In this paper an implementation of Yens algorithm is presented. Both the original algorithm and this implementation present computational complexity order when considering a worst-case analysis. However, computational experiments are reported, which allow to conclude that in practice this new implementation outperforms two other, Perkos implementation and a straightforward one.AMS classification: 05C38, 05C85, 68R10, 90C27.Ernesto Q.V. Martins: Sadly, the author passed away in November, 2000.Marta M.B. Pascoal: The research of Marta Pascoal was developed within CISUC and partially supported by the Portuguese Ministry of Science and Technology (MCT), under PRAXIS XXI Project of JNICT.