Multidimensional NMR spectroscopy for the study of histone H4-Ni(II) interaction

The N-terminal 30-amino acid tail of histone H4, a nuclear protein, was studied as a model for the interaction of this protein with Ni(ii) ions. The behaviour of the ends-blocked Ac-SGRGKGGKGLGKGGA(15)K(16)R(17)H(18)R(19)KVLRDNIQGIT-Am fragment towards Ni(ii) was analyzed with multidimensional NMR (1D, 2D TOCSY, NOESY) and UV-Vis spectroscopy. As expected, the coordination involved the imidazolic nitrogen of the His(18) residue and the three deprotonated amidic nitrogens of the His(18), Arg(17) and Lys(16) residues, respectively. A model for the structure of the complex was calculated from the inter-residual NOEs recorded in 2D NOESY spectra. The structure obtained shows that the interaction with the metal is responsible for deep changes in the conformation of the peptide, blocking the side chain of Arg(17) and Lys(16) residues above the coordination plane. These structural modifications may be physiologically relevant to the mechanism of nickel carcinogenesis.     

Applications of Pulsed‐Gradient Spin‐Echo (PGSE) Diffusion Measurements in Organometallic Chemistry

Diffusion data from pulsed‐field gradient spin‐echo (PGSE) methods are shown to be qualitatively useful in the investigation of problems involving unknown molecular aggregation and/or the nature of inter‐ionic interactions in metal complexes. For charged species possessing anions such as PF, BF, CF₃SO or BArF⁻, both ¹⁹F‐ and ¹H‐PGSE methods offer a valid alternative and, sometimes, unique view of gross and subtle solution molecular structure and dynamics. Problems associated with solvents, concentration, and reproducibility are discussed.     

A Gas-Phase Model for the Pt+-Catalyzed Coupling of Methane and Ammonia

What exactly are the elementary steps in the Pt-catalyzed coupling of methane and ammonia (Degussa process) shown on the right? Mass spectrometry and ab initio theory have been used to probe the mechanistic details of this technically important synthesis of hydrogen cyanide.     

Structural Studies of a N‐[(N‐Unsubstituted Pyrrole‐3‐carbonyl)oxy]benzamide and its Precursor Spiro[isoxazole‐4,3′‐pyrrole]

The structures of 6‐methyl‐4,8,9‐triphenyl‐2‐oxa‐3,7‐diazaspiro[4.4]nona‐3,6‐dien‐1‐one ( 3 ) and N‐[(2‐Methyl‐4,5‐diphenyl‐1H‐pyrrole‐3‐carbonyl)oxy]benzamide ( 4 ) were established by X‐ray crystal‐structure analysis. A significant improvement in the procedure currently available for the synthesis of these compounds is described. Ab initio and DFT calculations were carried out on the compound 4 and its precursor 3 , and compared with X‐ray results. In particular, to relate structural features to biological properties, the conformational characteristics and rotational barrier of compound 4 were studied.     

KAM for Reversible Derivative Wave Equations

We prove the existence of Cantor families of small amplitude, analytic, linearly stable quasi-periodic solutions of reversible derivative wave equations.     

Free energy and states of fractional-order hereditariness

Complex materials, often encountered in recent engineering and material sciences applications, show no complete separations between solid and fluid phases. This aspect is reflected in the continuous relaxation time spectra recorded in cyclic load tests. As a consequence the material free energy cannot be defined in a unique manner yielding a significative lack of knowledge of the maximum recoverable work that can extracted from the material. The non-uniqueness of the free energy function is removed in the paper for power-laws relaxation/creep function by using a recently proposed mechanical analogue to fractional-order hereditariness.     

Colloidal Surface Active Maghemite Nanoparticles for Biologically Safe CrVI Remediation: from Core‐Shell Nanostructures to Pilot Plant Development

The present study is aimed at the exploration of achievable improvements for Cr^VI ex situ and in situ water remediation by using novel naked colloidal maghemite (γ‐Fe₂O₃) nanoparticles (surface active maghemite nanoparticles, SAMNs). The reliability of SAMNs for Cr^VI binding and removal was demonstrated, and SAMN@Cr^VI complex was characterized, as well as the covalent nature of the absorption was unequivocally proved. SAMNs were structurally and magnetically well conserved after Cr^VI binding. Thus, in consideration of their affinity for Cr^VI, SAMNs were exploited in a biological model system, mimicking a real in situ application. The assay evidenced a progressive reduction of revertant colonies of Salmonella typhimurium TA100 strain, as maghemite nanoparticles concentration increased, till the complete suppression of Cr^VI mutagen effect. Finally, an automatic modular pilot system for continuous magnetic removal and recovery of Cr^VI from water is proposed. SAMNs, thanks to their colloidal, binding, and catalytic properties, represent a promising tool as a reliable nanomaterial for water remediation by Cr^VI.