Base promoted isomerization of aziridinyl ethers: a new access to alpha- and beta-amino acids

Aziridinyl ethers are selectively and easily converted to either amino vinyl ethers or alkoxy allylamines by treatment with mixed metal bases (superbases).     

Subcellular detection and localization of the drug transporter P-glycoprotein in cultured tumor cells

In vitro studies on the cellular location of P-glycoprotein (Pgp) are reported with the aim to clarify the relationship between its intracellular expression and the multidrug resistance (MDR) level of tumor cells. Pgp was found abnormally expressed on the plasma membrane of tumor cells with "classical" MDR phenotype. However, Pgp was also often detected on the nuclear envelope and on the membrane of cytoplasmic organelles. The hypothesis that this drug pump maintains a transport function when located in these compartments, is still under debating. Our results, together with those obtained by other researchers, demonstrate that cytoplasmic Pgp regulates the intracellular traffic of drugs so that they are no more able to reach their cellular targets. In particular, we revealed that in MDR breast cancer cells (MCF-7) a significant level of Pgp was expressed in the Golgi apparatus. A similar result was found in human melanoma cell lines, which never undergone cytotoxic drug treatment and did not express the transporter molecule on the plasma membrane. A strict relationship between intracellular Pgp and intrinsic resistance was demonstrated in a human colon carcinoma (LoVo) clone, which did not express the drug transporter on the plasma membrane. Finally, a structural and functional association between Pgp and ERM proteins has been discovered in drug-resistant human T- lymphobastoid cells (CEM-VBL 100). Our findings strongly suggest a pivotal role of the intracytoplasmic Pgp in the transport of drugs into cytoplasmic vesicles, thus actively contributing to their sequestration and transport outwards the cells. Thus, intracellular Pgp seems to represent a complementary protective mechanism of tumor cells against cytotoxic agents.     

First-principles theory of the EPR g tensor in solids: defects in quartz

A theory for the reliable prediction of the EPR g tensor for paramagnetic defects in solids is presented. It is based on density functional theory and on the gauge including projector augmented wave approach to the calculation of all-electron magnetic response. The method is validated by comparison with existing quantum chemical and experimental data for a selection of diatomic radicals. We then perform the first prediction of EPR g tensors in the solid state and find the results to be in excellent agreement with experiment for the E(1)(prime) and substitutional phosphorus defect centers in quartz.     

13C NMR examination of some N-thioaroylmorpholine–bromine adducts

The ¹³C NMR chemical shifts of three N-thioaroylmorpholine–bromine adducts, previously used as synthetic intermediates, are compared and discussed in the light of the corresponding shifts of the parent thioamides and suitable model compounds. Chemical shift changes are interpreted in terms of the electronic perturbation resulting from bromine coordination at sulphur.     

1H NMR spectral properties and conformational preferences of some 1,2,9,10,17,18,25,26-octathia[2.2.2.2]-metacyclophanes

The stereochemistry in solution of three octathia[2.2.2.2]metacyclophanes has been investigated by means of ¹H NMR spectroscopy. The results lead to the conclusion that the saddle or crown conformation is preferred for these compounds, depending on the substitution pattern of the constituent aromatic rings.     

Alcune osservazioni su varieta' algebriche associate A corpi di numeri

Two methods are indicated how to associate abelian or quasi abelian manifolds to number fields.     

Blowing-up orientato

Summary In this paper we define a new kind of blowing-up, as a functor from the category of real analytic spaces to the category of real semianalytic spaces, in such a way that orientability is preserved. Then we prove an existence theorem for ?oriented blowing-ups? of real analytic spaces.

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Riassunto In questo articolo si definisce un nuovo tipo blowing-up, come un funtore dalla categoria degli spazi analitici reali alla categoria degli spazi semianalitici reali, in modo tale che l'orientabilità sia preservata. Si dimostra quindi un teorema di esistenza per blowing-ups orientati di spazi analitici reali.

     

Quenching and hardening in the transverse quasi-elastic peak

We study in the RPA framework the collective response of symmetric, infinite nuclear matter to a spin-isospin sensitive probe with both σ · q and σ × q couplings. The two responses, similar in the low-q region, differ markedly for moderate momenta (?1 fm^?1). Indeed the collective effect manifests itself quite differently in the two responses; whereas the longitudinal one displays a softening and an enhancement (due to the attractive character of the associated particle-hole force), the transverse response is quenched and hardened with respect to the free Fermi gas. The existing experimental data, which we analyze, are compatible with our results. We also explore the total strengths and find that for repulsive forces they are appreciably reduced by the RPA correlations. A large part of this quenching comes from the Δ-excitation (LLEE effect), but some reduction is still present even when the nucleonic degrees of freedom are neglected. This illustrates a violation of strength conservation brought about by the RPA correlations in the spin-isospin channel.