Interactions between Oxygen Lone-Pair Orbitals and Double-Bond π-Orbitals in β,γ-Unsaturated,Bicyclic Ketones; a PE-Spectroscopic Investigation

The HE(Iα) photoelectron (PE) spectra of 2,3,5,6-tetramethylidene-2-bicyclo[2.2.1]heptanone ( 12 ), 5,6-dimethylidene-2-bicyclo[2.2.1]heptanone ( 14 ), 5,6-dimethylidene-2-bicyclo[2.2.2]octanone ( 16 ), and 5,6,7,8-tetramethylidene-2-bicyclo[2.2.2]octanone ( 17 ) have been recorded, Comparison with the PE data of other β,γ-unsaturated ketones and parent alkenes, and with the result of ab initio STO-3G calculations, confirm the existence of significant interactions between the oxygen lone-pair orbital n_o and the double-bond π orbital(s). It is argued that the major contributions to the basis energy shifts and to the cross term between the n_o and π orbitals are due to a ‘through-bond’ mechanism.     

Un problema al contorno per una classe di operatori ellittico-parabolici di ordine2m

Summary In this paper, boundary-value problems for degenerate elliptic parabolic operators of order 2m are discussed. An existence theorem is proved, with the help of a non trivial induction argument (substantially, with respect to the order of certain derivatives) and of a ? small parameter-method ?.

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Entrata in Redazione il 28 novembre 1973.

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Lavoro eseguito con contributo del C.N.R. nell'ambito del Gruppo di Ricerca per l'Analisi Funzionale.     

Physical properties of high-nuclearity metal cluster compounds

Metal cluster compounds are composed of large macromolecules, which consist of a metal core (cluster) containing a certain number (n=6–560) of metal atoms, to which core a shell of ligands is coordinated. They provide excellent model systems for an assembly of identical metal clusters, embedded in a dielectric matrix. We discuss a number of physical properties of these materials.     

Computational study of the catalytic domain of human neutrophil collagenase. specific role of the S3 and S'3 subsites in the interaction with a phosphonate inhibitor

Human neutrophil collagenase (HNC, MMP-8) is one of the target enzymes for drug treatment of pathologic extracellular matrix degradation. Peptidomimetic inhibitors bind in the S-side of the enzyme active site occupying the S ₁primary specificity pocket by their large hydrophobic side-chains. The crystal structure of the complex between the catalytic domain of MMP-8 and Pro-Leu-l-Trp^P(OH)₂(PLTP) showed that this phosphonate inhibitor binds in the S side of the active site. This finding was unexpected since it represents the first example of accommodation of the bulky Trp indolyl chain in the S₁rather than in the S ₁subsite. Dynamical and structural factors favouring this uncommon mode of binding were therefore investigated.MD simulations performed on the uncomplexed enzyme show that its structure in aqueous solution is only slightly different from the crystal structure found in the complex with PLTP. ED analysis of the MD simulations, performed on PLTP alternatively interacting with the S- or S-side of the active site, shows that the enzyme fluctuation increases in both cases. The main contribution to the overall enzyme fluctuation is given by the loop 164–173. The fluctuation of this loop is spread over more degrees of freedom when PLTP interacts with the S-side. This dynamical factor can enhance the preference of PLTP for the S subsites of MMP-8. MD simulations also show that ligation of PLTP in the S subsites is further favoured by better zinc chelation, a cation- interaction at the S₃subsite and unstrained binding conformations. The role of the S₃, S ₃and S ₁subsites in determining the inhibitor binding is discussed.     

Endopolysaccharides from Ganoderma resinaceum, Phlebia rufa, and Trametes versicolor Affect Differently the Proliferation Rate of HepG2 Cells

Fungi have been used for medicinal purposes for long time by Asian countries, being a putative source of powerful new phytopharmaceuticals such as polysaccharides. The aim of this study was to extract endopolysaccharides (IPS) from Ganoderma resinaceum, Phlebia rufa, and Trametes versicolor, grown under submerged culture, to compare crude IPS production, total carbohydrate, and protein yield, and to study the effect of these IPS on HepG2 cells proliferation rate. Total biomass produced by G. resinaceum, P. rufa, and T. versicolor was (in gram per liter) 3.32?±?0.80, 5.42?±?0.58, and 4.2?±?1.29 and the IPS yield (as the biomass percent) was 9.9?±?0.05, 29.0?±?6.3, and 9.1?±?3.1 %, respectively. Characterization of IPS has shown different proportion between total sugar and protein being, on average 6.04, 10.74, and 22.62, for G. resinaceum, T. versicolor, and P. rufa, respectively. The IPS effect, at 50, 100, and 200 μg?mL^?1 on HepG2 cell growth and viability was negligible for G. resinaceum and P. rufa but, in the case of T. versicolor, 200 μg?mL^?1 of IPS evoked 40 % reduction on cell growth. The results suggest that the intracellular polysaccharides from T. versicolor are a potential source for bioactive molecules with anti-proliferative properties.     

Description and validation of an analytical method for the determination of paromomycin sulfate in medicated animal feeds

A procedure for the extraction of paromomycin from different animal feed matrices (rabbit, chicken, pig feeds) and its subsequent determination via a reversed-phase ion-pair HPLC separation coupled with pulsed amperometric detection is described. The procedure optimised in terms of the extracting solvent and the solid phase extraction stationary phase allows the total recovery of the aminoglycoside antibiotic. The criteria used for the validation of the analytical method applied to the cited matrices are the linear dynamic range of the response, the detection limit, the repeatability, the intermediate repeatability and the accuracy. A comparison with a method described in the literature for the bulk analysis of this antibiotic is made.     

Correction: An exchange coupled meso–meso linked vanadyl porphyrin dimer for quantum information processing

Correction for ‘An exchange coupled meso–meso linked vanadyl porphyrin dimer for quantum information processing’ by Davide Ranieri et al., Chem. Sci., 2022, https://doi.org/10.1039/d2sc04969d.

During the editorial production of the finished article, the graphics associated with Fig. 3(a) and (b) were inadvertently switched.Open in a separate windowFig. 3Room temperature angular-dependent CW EPR X-band spectra of (a) m-[VO(TrPP)]₂ and (b) o-[VO(TrPP)]₂ for crystal rotations around three orthogonal axes. For both panels, the upper row shows the 2D experimental EPR contour plots for the three rotations, acquired with a 3° step; the lower row shows representative EPR spectra (black lines) for the three rotations – from 0° to 180° every 15° – together with the best spectral simulations (red lines) obtained by using |J| = 0.01 (0.005) cm⁻¹ and |J| = 0.05 (0.01) cm⁻¹ for (a) and (b), respectively. Experimental frequency: 9.40 GHz for (a), 9.87 GHz for (b).The intended version of Fig. 3 is shown below, and replaces that of the original article:The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers.