Comparative molecular field analysis of protein tyrosine phosphatase low-molecular-weight substrates

A set of 25 low-molecular-weight substrates for protein tyrosine phosphatase PTP1 has been investigated by comparative molecular field analysis (CoMFA). The quality of the model was assessed by cross-validations, predictions for a test set of substrates, bootstrapping, randomization of biological data, grid characteristics tests, and comparison with the X-ray-determined binding site of a closely related enzyme. The CoMFA study provides new insight into the steric and electrostatic factors influencing binding around the active site in protein tyrosine phosphatase and complement existing information available from X-ray data.     

Gruppi Policiclici Dotati di un Automorfismo Uniforme di Ordinepq

An automorphismϕ of a groupG is said to be uniform il for everyg ∈G there exists anh ∈G such thatG=h ⁻¹ h ^ρ . It is a well-known fact that ifG is finite, an automorphism ofG is uniform if and only if it is fixed-point-free. In [7] Zappa proved that if a polycyclic groupG admits an uniform automorphism of prime orderp thenG is a finite (nilpotent)p′-group. In this paper we continue Zappa’s work considering uniform automorphism of orderpg (p andq distinct prime numbers). In particular we prove that there exists a constantμ (depending only onp andq) such that every torsion-free polycyclic groupG admitting an uniform automorphism of orderpq is nilpotent of class at mostμ. As a consequence we prove that if a polycyclic groupG admits an uniform automorphism of orderpq thenZ _μ (G) has finite index inG.

Al professore Guido Zappa per il suo 90⁰ compleanno     

Effect of lithium complexation by 12-crown-4 on the regioselectivity of the attack of GEM-dichloroallyl-lithium on some carbonyl compounds

Substituted benzaldehydes and acetophenone preferentially attack the γ position of gem-dichloro allyl anion, but show a significantly increased -selectivity if 12-crown-4 is present. This behaviour is discussed on the basis of theoretical computations.     

Collective spin states in the electron gas in different dimensions and geometries

We study spin longitudinal and transverse linear response of the 3-dimensional electron gas, metal clusters and quantum dots. When the systems are spin unpolarized in the ground state, a low energy collective state emerges in finite size systems due to the discrete shell structure, whereas it is absent in the bulk due to the Landau damping. In the case of spin polarization of the ground state a collective state is present also in the bulk and a family of new collective states appears in finite size systems. Presented by E. Lipparini at the International Conference on “Atomic Nuclei and Metallic Clusters”, Prague, September 1–5, 1997.     

Synthesis of 4-N-alkyl and ribose-modified AICAR analogues on solid support

Herein, we report the solid-phase synthesis of several 5-aminoimidazole-4-(N-alkyl)carboxamide-1-ribosides (4-N-alkyl AICARs) and the corresponding 2′,3′-secoriboside derivatives. The method uses the N-1-dinitrophenyl-inosine 5′-bonded to a solid support. This inosine derivative has the C-2 of the purine base strongly activated towards the attack of N-nucleophiles thus allowing the preparation of several N-1 alkylated inosine supports from which a small library of 4-N-alkyl AICAR derivatives has been synthesized. A set of new 4-N-alkyl AICA-2′,3′-secoriboside derivatives have also been obtained in high yields by solid-phase cleavage of the 2′,3′-ribose bond.     

On the notion of bimodel for functorial semantics

We discuss the notion of bimodel in order to obtain a classification of the equivalences between categories of models in the sense of functorial semantics.Research supported by NATO grant 900959 and FNRS grant 1.5.181.90F