RotAnal: una nuova applicazione per lo studio conformazionale di molecole organiche flessibili

La diffusione di PC ad alte prestazioni e la disponibilità di efficienti pacchetti software quantomcccanici (GAMESS. Gaussian, ecc.) permette oggi il calcolo accurato della struttura geometrica e delle grandezze termodinamiche di molecole di medie dimensioni sia in fase gassosa che condensata. In pratica, però, tale potenzialità è limitata dal fatto che la maggior parte delle molecole è flessibile, con la conseguente esistenza di differenti geometrie energeticamente stabili e pertanto, in molti casi, significativamente popolate (rotameri). Ne consegue che qualunque studio strutturistico che voglia essere realistico esige invariabilmente l'esame dello spazio conformazionale, e ciò è purtropp…

CPMAS 13C NMR Characterization of Leaves and Litters from the Reafforestated Area of Mustigarufi in Sicily (Italy)

Reafforestation is generally based on the planting of exotic fast growing tree species suitable for adapting to even harsh environments. Once the introduced plants ameliorate soil conditions, they can be progressively replaced by au- tochthonous plant species. Reafforestation is applied worldwide. However, only few studies on the effect of reafforesta- tion on lands from Mediterranean regions are available. This paper reports the characterization by cross polarization 13C NMR spectroscopy of fresh leaves and superficial litters from a reafforestated area in central Sicily (Italy). NMR assign- ment is attempted. A differentiation among the molecular systems within leaves and litters is also …

Gas-phase ion chemistry of protonated melatonin

The gas-phase ion chemistry of protonated melatonin has been investigated by mass spectrometric (MS) techniques involving chemical ionisation, fast atom bombardment and electrospray ionisation. Either naturally- occurring or collision-induced decomposition e-D derivatives obtained by exchange with D(2)O. The analysis of experimental results allows definite pathways for the formation of the ion at m/z 174 to be assigned and sheds some more light on the overall fragmentation pathways. Experiments on labelled derivatives evidenced H-D scrambling processes during fragmentation

Gas-phase ion chemistry of protonated melatonin

The gas-phase ion chemistry of protonated melatonin has been investigated by mass spectrometric (MS) techniques involving chemical ionisation, fast atom bombardment and electrospray ionisation. Either naturally-occurring or collision-induced decomposition experiments have been carried out using side chain tetra-deuterium-labelled derivatives, as well as the corresponding N–D derivatives obtained by exchange with D2O. The analysis of experimental results allows definite pathways for the formation of the ion at m/z 174 to be assigned and sheds some more light on the overall fragmentation pathways. Experiments on labelled derivatives evidenced H–D scrambling processes during fragmentation.

Rimozione del pesticida oxadixyl da una soluzione acquosa

Il micelio di Phomopsis helianthi, un Ascomicete, è stato trattato con NaOH all'ebollizione ottenendo una frazione insolubile essenzialmente composta da chitosano e glucani. Il materiale ottenuto è stato valutato come agente per la rimozione di pesticidi da una soluzione acquosa. Il pesticida usato nella presente sperimentazione è l'oxadixyl, il quale ha una solubilità in acqua pari a 3.4 g/L. L'efficienza della biomassa è stata provata usando 20, 40 ed 80 mg di materiale fino ad una concentrazione di 3 mM. La biomassa risulta in grado di recuperare fino a 6 mg di oxadixyl per grammo di materiale assorbente. l risultati sperimentali mostrano un'ottima correlazione nell'ambito del modello de…

Palladium-Catalysed Intermolecular Direct C–H Bond Arylation of Heteroarenes with Reagents Alternative to Aryl Halides: Current State of the Art

Abstract: This unprecedented review with 322 references provides a critical up-to-date picture of the Pd-catalysed intermolecular direct C–H bond arylation of heteroarenes with arylating reagents alternative to aryl halides that include aryl sulfonates (aryl triflates, tosylates, mesylates, and imidazole-1-sulfonates), diaryliodonium salts, [(diacetoxy)iodo]arenes, arenediazonium salts, 1-aryltriazenes, arylhydrazines and N’-arylhydrazides, arenesulfonyl chlorides, sodium arenesulfinates, arenesulfinic acids, and arenesulfonohydrazides. Particular attention has been paid to summarise the preparation of the various arylating reagents and to highlight the practicality, versatility, and limit…

Effetto della flessibilità conformazionale sull'equilibrio di interconversione tra aldosi e chetosi

Le reazioni di interconversione tra gli aldosi e i chetosi sono importanti trasformazioni, di interesse biochimico, che si presentano in parecchi stadi sia del catabolismo (glicolisi, via dei pentosofosfati) che dell'anabolismo (ciclo di Calvin) dei glucidi. Il meccanismo di reazione accettato, che coinvolge intermedi 1,2-endiolici, è talvolta riferito come una doppia tautomeria acido-catalizzata. Poiché, d'altro canto, reagenti, prodotti ed intermedi presentano tutti un'elevata flessibilità molecolare, ogni indagine computazionale sufficientemente accurata deve comprendere necessariamente l'analisi conformazionale di ciascun substrato coinvolto nell'equilibrio chimico. Tale analisi è stata…

Ab initio conformational study of 2,2′:5′,2″-terthiophene

Abstract The conformers of 2,2′:5′,2″-terthiophene were determined through ab initio MO full geometry optimization with a 6-31G * basis set. Different minima were found corresponding to twisted anti, anti, syn, anti and syn, syn structures. An estimate of the interconversion rate between conformers was performed.

Structural and spectroscopic characterisation of 2-(2'-hydroxybenzoyl)pyrrole and its O-methyl derivative

Abstract Density functional theory calculations on the tautomeric and conformational equilibria of 2-(2′-hydroxybenzoyl)pyrrole (HBP) and 2-(2′-methoxybenzoyl)pyrrole (MBP) were performed. Moreover, the experimental IR and UV spectra of the same compounds were recorded and compared with the theoretical data. The presence of an intramolecular hydrogen bond in HBP can be related to the biological activities of some of its derivatives.

The electronic spectra of 2-(2′-hydroxybenzoyl)pyrrole and 2-(2′-methoxybenzoyl)pyrrole: a theoretical study

The gas-phase electronic spectra of 2-(2 0 -hydroxybenzoyl)pyrrole and 2-(2 0 -methoxybenzoyl)pyrrole have been determined using multiconfigurational perturbation theory (CASPT2). Solvatochromic spectral shifts for these molecules have been measured in cyclohexane and methanol and the electrostatic components of these shifts have been estimated using the vertical electrostatic model (VEM 4.2) developed for the configuration interaction with single excitations model implemented with the intermediate neglect of differential overlap Hamiltonian (CIS/INDO/ S2). Comparison between theory and experiment and an interpretation of the main spectral differences between the two substituted pyrroles an…

An Updated Review on the Synthesis and Antibacterial Activity of Molecular Hybrids and Conjugates Bearing Imidazole Moiety

The rapid growth of serious infections caused by antibiotic resistant bacteria, especially the nosocomial ESKAPE pathogens, has been acknowledged by Governments and scientists and is one of the world’s major health problems. Various strategies have been and are currently investigated and developed to reduce and/or delay the bacterial resistance. One of these strategies regards the design and development of antimicrobial hybrids and conjugates. This unprecedented critical review, in which our continuing interest in the synthesis and evaluation of the bioactivity of imidazole derivatives is testified, aims to summarise and comment on the results obtained from the end of the 1900s until Februa…

Metal ion adsorption by phomopsis sp. Biomaterial in laboratory experiments and real Wastewater Treatments

An insoluble material of polysaccharidic nature has been obtained by thermal alkali treatment of the filamentous fungus Phomopsis sp. FT-IR spectrum of the resulting material as well as its nitrogen content suggest that chitosan and glucans are the main components of the biomaterial. Information on Lewis base sites has also been obtained and used as a guideline in the evaluation of the complexing ability against a number of metal ions in aqueous media at pH in the range 4--6. Results indicate that after 24h contact time, up to 870 micromol/g of lead, 390 micromol/g of copper, 230 micromol/g of cadmium, 150 micromol/g of zinc and 110 micromol/g of nickel ions are adsorbed into the material. …

STUDIO QUANTOMECCANICO STRUTTURALE E CONFORMAZIONALE DELL'INSETTICIDA ROTENONE

Gas-phase ion chemistry of protonated melatonin: naturally occurring and collision induced fragmentation

Current Advances in the Synthesis and Biological Evaluation of Pharmacologically Relevant 1,2,4,5-Tetrasubstituted-1H-Imidazole Derivatives

:In recent years, the synthesis and evaluation of the biological properties of 1,2,4,5-tetrasubstituted-1H-imidazole derivatives have been the subject of a large number of studies by academia and industry. In these studies it has been shown that this large and highly differentiated class of heteroarene derivatives includes high valuable compounds having important biological and pharmacological properties such as antibacterial, antifungal, anthelmintic, anti-inflammatory, anticancer, antiviral, antihypertensive, cholesterol-lowering, antifibrotic, antiuricemic, antidiabetic, antileishmanial and antiulcer activities.:The present review with 411 references, in which we focused on the literatur…

Studio quantomeccanico strutturale e conformazionale di piretrine di origine naturale

Removal of Pesticide Oxadixyl from an Aqueous Solution

ABSTRACT The mycelium of Phomopsis helianthi (Ascomycete) was hydrolyzed with boiling NaOH to give an insoluble fraction composed of chitosan and glucans. The biomass obtained was tested as an agent for the removal of pesticides from an aqueous solution. Oxadixyl, which has a solubility in water of 3400 mg L−1, has been chosen as a hydrophilic organic contaminant model. The new, cheap material was demonstrated to recover up to 6 mg of oxadixyl per gram of adsorbent. The experimental data show an excellent correlation with the Langmuir isotherm model.

Adsorbimento di pesticidi organofosforici in suoli con differenti caratteristiche chimico fisiche.

Studio quantomeccanico della struttura e delle conformazioni di pesticidi organofosforici

pesticidi,organofosforici,quantomeccanico

Oxidative halogenation of substituted pyrroles with Cu(II). PartIV.Bromination of 2-(2′-hydroxybenzoyl)pyrrole. A new synthesis of bioactive analogs of monodeoxypyoluteorin

The selective bromination with copper(II) bromide of the pyrrole ring in 2-(2'-hydroxybenzoyl)pyrrole (II) in the heterogeneous phase is des- cribed giving in almost quantitative yield the 4,5-dibromo derivative (VI). The subsequent introduction of halogen into the phenol moiety was observed when the reaction was perfomed in the homogeneous phase with an excess of halogenating agent. The pentabromo derivative (IX), a com- pound very active against Staphylococcus aureus (mic=17 nmoles per dm -3 ), was obtained by exhaustive bromination of the title compound. Poor yields of chloro derivatives of (II) were obtained by reaction of the parent compound with copper(II) chloride

Caratterizzazione della componente volatile rilasciata da sostanza organica naturale di suoli vulcanici

Il suolo è una matrice caratterizzata da notevole complessità chimico-fisica. Tra le varie componenti, la sostanza organica naturale (NOM) gioca un ruolo fondamentale nelle interazioni con contaminanti di natura organica ed inorganica. La NOM è attualmente considerata una associazione supramolecolare di sistemi organici con un peso molecolare non superiore a 1000-2000 Da. La sua caratterizzazione è tradizionalmente effettuata mediante l’ausilio di tecniche cromatografiche e spettroscopiche. La verifica dell’allontanamento di molecole a basso peso molecolare all’aumento della temperatura, nell’intervallo 40-100 °C, è stata condotta con tecniche di microestrazione in fase solida in spazio di …