The relationship between the antimicrobial activity of eugenol and the LPETG peptide structure and associated analysis for docking purposes

Sortase A is responsible for the virulence of Gram-positive pathogens, including staphylococci and streptococci. The LPETG is the peptide surface anchor signal for Sortase A. The inhibitors of this enzyme shared similar binding pattern with substrate LPETG. Eugenol and its derivatives may act as sortase A inhibitor. The antimicrobial activity of eugenol and its derivatives was tested in vitro against bacterial strains: Staphylococcus aureus, Streptococcus mutans and Escherichia coli. All the tested derivatives demonstrated antimicrobial activity. Differences between derivatives in terms of in vitro activity and interactions between the amino acid residues were correlated in the docking analysis for the same derivatives. According to the relationship observed in this study between the antimicrobial activity of eugenol and the LPETG peptide structure, some of the eugenol derivatives proved to be more active inhibiting sortase A than eugenol against microorganisms when tested at the same concentrations.     

Inferring Excitatory and Inhibitory Connections in Neuronal Networks

The comprehension of neuronal network functioning, from most basic mechanisms of signal transmission to complex patterns of memory and decision making, is at the basis of the modern research in experimental and computational neurophysiology. While mechanistic knowledge of neurons and synapses structure increased, the study of functional and effective networks is more complex, involving emergent phenomena, nonlinear responses, collective waves, correlation and causal interactions. Refined data analysis may help in inferring functional/effective interactions and connectivity from neuronal activity. The Transfer Entropy (TE) technique is, among other things, well suited to predict structural interactions between neurons, and to infer both effective and structural connectivity in small- and large-scale networks. To efficiently disentangle the excitatory and inhibitory neural activities, in the article we present a revised version of TE, split in two contributions and characterized by a suited delay time. The method is tested on in silico small neuronal networks, built to simulate the calcium activity as measured via calcium imaging in two-dimensional neuronal cultures. The inhibitory connections are well characterized, still preserving a high accuracy for excitatory connections prediction. The method could be applied to study effective and structural interactions in systems of excitable cells, both in physiological and in pathological conditions.     

Synthesis of new enantiomerically pure C1- and C2-symmetric N-alkyl-benzimidazolium and thiazolium salts

Starting from the commercially available enantiopure (1S,2S)-2-amino-1-phenyl-1,3-propanediol novel enantiomerically pure benzimidazoles were prepared; N-alkylation gave chiral benzimidazolium salts, which were tested in asymmetric benzoin condensations. The synthesis of conceptually new, enantiomerically pure, C₂ symmetric bis-thiazolium and bis-benzimidazolium salts was also developed. These new chiral heterocycles were employed as catalysts in the asymmetric dimerisation of benzaldehyde to give benzoin with moderate enantioselectivity.     

Horseradish peroxidase catalyzed oxidative cross-coupling reactions: the synthesis of ‘unnatural’ dihydrobenzofuran lignans

The possibility to afford by a biomimetic reaction ‘unnatural’ products, which could offer a better bioactivity profile than natural analogues, is outlined and the first applications to the synthesis of lignans and related compounds have been reported. Here we describe the synthesis of new heterodimers, having a phenylcoumaran skeleton, by horseradish peroxidase catalyzed cross-coupling reactions of methyl esters of substituted hydroxycinnamic acids.     

Characterization of waterlogged wood by NMR and GPC techniques

Anaerobic erosion bacteria can slowly degrade waterlogged wood, causing a loss of cellulose and hemicellulose. During this process, lignin can also be altered. For this reason, the chemical characterization of waterlogged archaeological wood is crucial for both the elucidation of the degradation processes and also the development of consolidation and conservation procedures.The complex structure of wood makes it practically impossible to dissolve wood in its native form in conventional molecular solvents. Ionic liquids can provide a homogeneous reaction medium for wood-based lignocellulosic materials. Highly substituted lignocellulosic esters and phosphite esters can be obtained under mild conditions by reacting pulverized wood dissolved in ionic liquid with either acyl chlorides or dioxaphospholanes in the presence of pyridine. As a result, the functionalized wood develops an enhanced solubility in molecular solvents, allowing for a complete characterization by means of spectroscopic and chromatographic techniques.In this study, archaeological woods and reference sound woods of the same taxa (Quercus and Arbutus unedo), along with the corresponding extracted lignin, were fully characterized by means of phosphorus NMR spectroscopy, two dimensional NMR spectroscopy and GPC analysis. The samples were collected from the Site of the Ancient Ships of San Rossore (Pisa, Italy), where many shipwrecks dating from 2nd century BC to 5th century AD have been discovered.The results highlighted a deeper and faster depolymerization of the polysaccharide matrix against a limited degradation of the lignin fraction. The use of innovative solvent system as the ionic liquid [amim]Cl enables to highlight chemical and morphologic changes in wood composition avoiding further degradation.     

Solvent effects on the vibrational activity and photodynamics of the green fluorescent protein chromophore: a quantum-chemical study

Vibrational activities in the Raman and resonance Raman spectra of the cationic, neutral, and anionic forms of 4'-hydroxybenzylidene-2,3-dimethyl-imidazolinone, a model compound for the green fluorescent protein chromophore, have been obtained from quantum-chemical calculations in vacuo and with the inclusion of solvent effects through the polarizable continuum model. It is found that inclusion of solvent effects improves slightly the agreement with experimental data for the cationic and neutral forms, whose spectra are qualitatively well-described already by calculations in vacuo. In contrast, inclusion of solvent effects is crucial to reproduce correctly the activities of the anionic form. The structural effects of solvation are remarkable both in the ground and in the lowest excited state of the anionic chromophore and influence not only the vibrational activity but also the photodynamics of the lowest excited state. CASPT2//CASSCF photoreaction paths, computed by including solvent effects at the CASSCF level, indicate a facile torsional deformation around both exocyclic CC bonds. Rotation around the exocyclic CC double bond is shown to lead to a favored radiationless decay channel, more efficient than that in gas phase, and which explains the ultrafast fluorescence decay and ground-state recovery observed in solution. Conversely, rotation around the exocyclic CC single bond accounts for the bottleneck observed in the ground-state recovery cycle. It is also speculated that the ultrafast radiationless decay channel would be hampered in protein for unfavorable electrostatic interactions and steric reasons.     

Asymmetric multicomponent copper catalyzed synthesis of chiral propargylamines

A three-component stereoselective reaction between an aldehyde, an amine and phenylacetylene to afford optically active propargyl amines in good yields was developed. The reaction is catalysed by copper complexes of enantiomerically pure bis-imines. The best results were obtained with imines readily prepared in very high yields from the commercially available binaphtyl diamine.

A very simple experimental procedure at room temperature allowed to obtain optically active propargyl amines in very good yields and enantioselectivity up to 75%. The extremely simple methodology and the mild reaction conditions, as well as the possibility of a modular approach for developing new and more efficient bis-imine-based chiral ligands make the present methodology very attractive.     

Plasma-induced graft-polymerization of polyethylene glycol acrylate on polypropylene substrates

A detailed study of argon plasma-induced graft-polymerization of polyethylene glycol acrylate (PEGA) on polypropylene (PP) substrates (membranes and films) is presented. The process consists of four steps: (a) plasma pre-activation of the PP substrates; (b) immersion in a PEGA solution; (c) argon plasma-induced graft-polymerization; (d) washing and drying of the samples. Influence of the solution and plasma parameters on the process efficiency evaluated in terms of amount of grafted polymer, coverage uniformity and substrates wettability, are investigated. The plasma-induced graft-polymerization of PEGA is then followed by sample weighting, water droplet adsorption time and contact angle measurements, attenuated total reflection infrared spectroscopy (ATR-IR), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) analyses. The stability of the obtained thin films was evaluated in water and in phosphate buffer saline (PBS) at 37 °C. Results clearly indicates that plasma-induced graft-polymerization of PEGA is a practical methodology for anti-fouling surface modification of materials.