A Selective HIV‐Protease Assay Based on a Chromogenic Amino Acid

(2S,3S)‐2‐Amino‐3‐hydroxy‐5‐(4‐nitrophenoxy)pentanoic acid ( 5 ) was prepared stereoselectively as the N‐Fmoc, O‐(tert‐butyl)‐protected derivative 5a in eleven steps from ethyl (E)‐4‐benzyloxypent‐2‐enoate ( 6 ). This protected amino acid was used for the solid‐phase peptide synthesis of oligopeptides, which serve as sequence‐specific chromogenic protease substrates when used in the presence of NaIO₄ and bovine serum albumin. The peptide 1 (KRAVNle 5  EANleNH₂ (Nle=norleucine)) allows detection of HIV‐protease activity spectrophotometrically at 405 nm.     

Search for supermassive magnetic monopoles with the MACRO detector at the gran sasso laboratory

We present the results of the search for supermassive magnetic monopoles with the MACRO experiment. Our detector is equipped with three independent subdetectors (liquid scintillation counters, limited streamer tubes and nuclear track detectors), operating in different ranges of monopole velocity. In several years of data taking no candidates were found; the present flux upper limits are the level of half the Parker Bound for β > 10⁻⁴; for 10⁻⁴ < β < 5 × 10⁻² the limit is the best existing.     

A new selective fluorescence chemosensor for Cu(II) in water

A new chemosensor for the Cu(II) ion has been realized by connecting via an amido bond an anthracenyl residue to the all cis 2,4,6-triamino-1,3,5-trihydroxycyclohexane ligand (TACI). This sensor is able to detect micromolar concentrations of Cu(II) ions in water at pH 7 without interference with many other divalent transition metal ions.     

Magnetic anomaly in UCN trapping: signal for neutron oscillations to parallel world?

Present experiments do not exclude that the neutron n oscillates, with an appreciable probability, into its invisible degenerate twin from a parallel world, the so-called mirror neutron n′. These oscillations were searched experimentally by monitoring the neutron losses in ultra-cold neutron traps, where they can be revealed by the magnetic field dependence of n–n′ transition probability. In this work we reanalyze the experimental data acquired by the group of A.P. Serebrov at Institute Laue–Langevin, and find a dependence at more than 5σ away from the null hypothesis. This anomaly can be interpreted as oscillation of neutrons to mirror neutrons with a timescale of few seconds, in the presence of a mirror magnetic field order 0.1 G at the Earth. This result, if confirmed by future experiments, will have deepest consequences for fundamental particle physics, astrophysics and cosmology.     

Stereoselective Synthesis of 1,3-Disaccharides through Diels-Alder Reactions: Part 2[ 1 ]: Convenient Protecting Groups for Heterodienes and Conformational Evaluations

Improved synthesis of 1,3-disaccharides, obtained diastereomerically pure by [4+2] hetero cycloadditions between glycals and α -thiono-β -keto-δ -lactones, has been reported. The choice of appropriate protecting groups for β -keto-δ -lactones, stable under cycloaddition conditions employed, sensibly shortened the synthesis of heterodienic precursors. The first example of a β -oxy-imino-δ -lactone synthesized from β -keto-δ -lactones was also reported. Molecular modeling and conformational evaluations about the cycloaddition features allowed tentatively rationalizing the experimental results.     

Essential coverings and triangulations

Sunto In questo lavoro si danno condizioni sufficienti per un ricoprimento di una varietà differenziabile V affinchè il suo nerbo abbia lo stesso tipo P.L. di V e si prova l'esistenza di una larga classe di siffatti ricoprimenti.

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The author is member of G.N.S.A.G.A. of the C.N.R. and partially supported by a N.A.T.O.-C.N.R. fellowship.     

Derivatives of Wronskians with applications to families of special Weierstrass points

Let be a flat proper family of smooth connected projective curves parametrized by some smooth scheme of finite type over . On every such a family, suitable derivatives along the fibers" (in the sense of Lax) of the relative wronskian, as defined by Laksov and Thorup, are constructed. They are sections of suitable jets extensions of the -th tensor power of the relative canonical bundle of the family itself.

The geometrical meaning of such sections is discussed: the zero schemes of the -th derivative () of a relative wronskian correspond to families of Weierstrass Points (WP's) having weight at least .

The locus in , the coarse moduli space of smooth projective curves of genus , of curves possessing a WP of weight at least , is denoted by . The fact that has the expected dimension for all was implicitly known in the literature. The main result of this paper hence consists in showing that has the expected dimension for all . As an application we compute the codimension Chow (-)class of for all , the main ingredient being the definition of the -th derivative of a relative wronskian, which is the crucial tool which the paper is built on. In the concluding remarks we show how this result may be used to get relations among some codimension Chow (-)classes in (), corresponding to varieties of curves having a point with a suitable prescribed Weierstrass Gap Sequence, relating to previous work of Lax.