Microwave-assisted, zinc-mediated peptide coupling of N-benzyl-α,α-disubstituted amino acids

Incorporation of the extremely hindered amino acid N-benzylaminoisobutyric acid into dipeptides under microwave irradiation with commercial zinc dust is described. A comparative survey of various methodologies for hindered peptide couplings was undertaken. The optimised coupling conditions were free from racemisation and applicable to other hindered amino acids.     

On the structure of superfields in a field theory on a supermanifold

In view of applications to the formulation of gauge field theories on supermanifolds, we study the relation between the sheaves of functions on a supermanifold M and its body manifold M ₀, respectively. The nonuniqueness of the local injections t: M ₀M is analysed in consideration of its role in supersymmetric field theories. A Banach space structure is given to the set of bounded, supersmooth, C ^k fields on M in order to get a rigorous formulation of variational principles for the class of theories under consideration.Research work partly supported by the National Group for Mathematical Physics (GNFM) of the Italian Research Council (CNR) and by the Italian Ministry of Public Education through the research project Geometria e Fisica.     

Study of sulphation of Candoglia marble by means of micro X-ray diffraction experiments

This research is aimed at assessing the particular kind of damage caused by the interaction between atmospheric pollution and the marble surface of a magnificent late gothic church, Milan Cathedral, restored in the early 1970s. On the basis of visual inspections and diagnostic investigations the facade appears to be seriously damaged by surface erosion and thick black crusts; biological crusts, micro-fractures and detachments are widely present.This paper reports on SR-μXRD data collected at the Synchrotron Radiation Source (SRS), Daresbury Laboratory, and at the European Synchrotron Radiation Source (ESRF) from selected samples, covered with black crusts, originating from the Milan Cathedral facade. Mineralogical maps of the deterioration layers have been recorded by two spatial resolutions (5–100 μm), from the bulk of the stone material to the outer layer of the black surface. These maps help in elucidating the mechanism of formation of the black crusts. PACS 33.20.Rm; 61.10.Eq; 61.10.Nz; 78.70.Ck     

Inhibition of Urease by Hydroquinones: A Structural and Kinetic Study

Hydroquinones are a class of organic compounds abundant in nature that result from the full reduction of the corresponding quinones. Quinones are known to efficiently inhibit urease, a Ni^II-containing enzyme that catalyzes the hydrolysis of urea to yield ammonia and carbonate and acts as a virulence factor of several human pathogens, in addition to decreasing the efficiency of soil organic nitrogen fertilization. Here, we report the molecular characterization of the inhibition of urease from Sporosarcina pasteurii (SPU) and Canavalia ensiformis (jack bean, JBU) by 1,4-hydroquinone (HQ) and its methyl and tert-butyl derivatives. The 1.63-Å resolution X-ray crystal structure of the SPU-HQ complex discloses that HQ covalently binds to the thiol group of αCys322, a key residue located on a mobile protein flap directly involved in the catalytic mechanism. Inhibition kinetic data obtained for the three compounds on JBU reveals the occurrence of an irreversible inactivation process that involves a radical-based autocatalytic mechanism.     

Structure of supermanifolds and supersymmetry transformations

After giving a global, constraint-free Lagrangian formulation of theN=1 superspace supergravity in terms of super fibre bundles and differential forms over a supermanifold, we show that the concept of body manifold of a supermanifold provides a natural manner to reduce the theory to spacetime. This reduction, however, is not canonical, and the various ways in which it can be done give rise to transformations of the field variables which generalise the known invariances of theN=1 spacetime supergravity under supersymmetry transformations and spacetime diffeomorphisms.Research partly supported by the Gruppo Nazionale per la Fisica Matematica of the Italian Research Council and by the Italian Ministry of Public Education through the research project Geometria e Fisica     

Observation of wave packet dichotomy and adiabatic stabilization in an optical waveguide

We report on the first experimental observation of wave packet dichotomy and adiabatic stabilization of light in a periodically bent optical waveguide in analogy with similar behavior of atoms in high-frequency strong laser fields.     

Generalized axisymmetric spacetimes

Properties of space-times admitting a two parameter abelian symmetry group acting on a null two-surface are investigated. Within this framework, a class of new solutions of Einstein's vacuum equations are found. Some analogies with the theory of black hole are pointed out.This work was carried out under the auspices of the National Group of Mathematical Physics of C.N.R.     

p-Adic valued quantization

This review covers an important domain of p-adic mathematical physics — quantum mechanics with p-adic valued wave functions. We start with basic mathematical constructions of this quantum model: Hilbert spaces over quadratic extensions of the field of p-adic numbers ? _p , operators — symmetric, unitary, isometric, one-parameter groups of unitary isometric operators, the p-adic version of Schrödinger’s quantization, representation of canonical commutation relations in Heisenberg andWeyl forms, spectral properties of the operator of p-adic coordinate.We also present postulates of p-adic valued quantization. Here observables as well as probabilities take values in ? _p . A physical interpretation of p-adic quantities is provided through approximation by rational numbers.     

The preparation of fluorescence-quenched probes for use in the characterization of human factor Xa substrate binding domains

The preparation and characterization by LCMS of a library of 55 fluorescence- quenched peptides is described. The peptides bear a terminal anthranilamide fluorophore and a penultimate 2,4-dinitrophenyl-L-lysine quencher, and will be used to probe the substrate binding domain of the human blood coagulation enzyme, factor Xa.     

Comments on limits of space-times

A coordinate-dependent investigation of limits of space-times is given. Different kinds of limits are found and analyzed. A criterion selecting limits which appear to be nothing but technical tricks is proposed. Finally, a method for generating new limits from a given family of metrics is examined.This work was carried out under the auspices of the National Group for Mathematical Physics of C.N.R.