Identification and structural characterization by LC‐ESI‐IONTRAP and LC‐ESI‐TOF of some metabolic conjugation products of homovanillic acid in urine of neuroblastoma patients

The levels of urinary catecholamine metabolites, such as homovanillic acid (HVA) and vanillylmandelic acid, are routinely used as a clinical tool in the diagnosis and follow‐up of neuroblastoma (NB) patients. Recently, in the Clinical Pathology Laboratory Unit of G. Gaslini Children Hospital, a commercial method that employs liquid chromatography coupled to electrochemical detection (LC‐EC) has been introduced for the measurement of these metabolites in the routine laboratory practice. Using this LC‐EC method, an unknown peak could be observed only in samples derived from NB patients. To investigate the nature of this peak, we used a combination of liquid chromatography‐time‐of‐flight mass spectrometry (LC‐TOF‐MS) and liquid chromatography‐ion trap tandem mass spectrometry (LC‐IT‐MS). The first approach was used to obtain the elemental composition of the ions present in this new signal. To get additional structural information useful for the elucidation of unknown compounds, the ion trap analyzer was exploited. We were able to identify not just one, but three unknown signals in urine samples from NB patients which corresponded to three conjugated products of HVA: HVA sulfate and two glucuronoconjugate isomers. The enzymatic hydrolysis with β‐glucuronidase confirmed the proposed structures, while the selective alkaline hydrolysis allowed us to distinguish the difference between phenol‐ and acyl‐glucuronide of HVA. The latter was the unknown peak observed in LC‐EC separations of urine samples from NB patients. Copyright © 2012 John Wiley & Sons, Ltd.     

Ultrafast dynamics of Cu(I)-phenanthrolines in dichloromethane

Transient absorption spectrometry of Cu(I)-phenanthrolines in CH2Cl2 reveals ligand-independent dynamic processes lasting 15 ps, which are associated with the peculiar structural rearrangements occurring for this class of compounds upon photoexcitation.     

Multivalent recognition of bis- and tris-Zn-porphyrins by N-methylimidazole functionalized gold nanoparticles

N-Methylimidazole-functionalized gold nanoparticles behave as multivalent ligands for porphyrin arrays with an increase in binding strength of up to three order of magnitude with respect to a monovalent system.     

Synthesis and optical properties of a poly(2′,5′-dioctyloxy-4,4′,4″- terphenylenevinylene) with high content of (Z) vinylene units

Poly(2′,5′-dioctyloxy-4,4′,4″-terphenylenevinylene) with (E) configuration of the vinylene double bonds was prepared by Suzuki-Miyaura polymerization of (E)-4,4′-dibromostilbene and 2,5-dioctyloxy-1,4-benzenediboronic acid. Attempts to extend this simple procedure to the synthesis of the polymer with (Z) configuration, starting from (Z)-4,4′-dibromostilbene, were unsuccessful. However, the use of (Z)-4,4′-diiodostilbene and a careful choice of Pd catalyst and experimental conditions, lead to a material with a >95/<5 (Z)/(E) ratio of vinylene units. The investigation of optical properties of both the (E) and (Z) polymers evidenced that (Z) linkages act as defects which reduce the effective conjugation length in the polymer backbone.     

Flexible protocol for the chemo- and regioselective building of pyrroles and pyrazoles by reactions of Danishefsky's dienes with 1,2-diaza-1,3-butadienes

The versatility of the Mukaiyama-Michael-type addition/heterocyclization of Danishefsky's diene with 1,2-diaza-1,3-butadienes was applied to the synthesis of both 4 H-1-aminopyrroles and 4,5 H-pyrazoles. Thus, the same reagents furnished different types of highly functionalized azaheterocycles essentially depending on their structure: as a matter of fact, R1 = COOR or CONR 2 differently affects the acidity of the proton at the adjacent carbon. An unexpected formation of 5 H-1-aminopyrroles from the reactions carried out in water was also observed.     

Heteroleptic copper(I) complexes coupled with methano[60]fullerene: synthesis, electrochemistry, and photophysics

Heteroleptic copper(I) complexes CuPOP-F and CuFc-F have been prepared from a fullerene-substituted phenanthroline ligand and bis[2-(diphenylphosphino)phenyl] ether (POP) and 1,1'-bis(diphenylphosphino)ferrocene (dppFc), respectively. Electrochemical studies indicate that some ground-state electronic interaction between the fullerene subunit and the metal-complexed moiety are present in both CuPOP-F and CuFc-F. Their photophysical properties have been investigated by steady state and time-resolved UV-vis-NIR luminescence spectroscopy and nanosecond laser flash photolysis in a CH2Cl2 solution and compared to those of the corresponding model copper(I) complexes CuPOP and CuFc and of the fullerene model compound F. Selective excitation of the methanofullerene moiety in CuPOP-F results in regular deactivation of the lowest singlet and triplet states, indicating no intercomponent interactions. Conversely, excitation of the copper(I)-complexed unit (405 nm, 40% selectivity) shows that the strongly luminescent triplet metal-to-ligand charge-transfer ((3)MLCT) excited state located at 2.40 eV is quenched by the carbon sphere with a rate constant of 1.6 x 10(8) s(-1). Details on the mechanism of photodynamic processes in CuPOP-F via transient absorption are hampered by the rather unfavorable partition of light excitation between the two chromophores. By determination of the yield of formation of the lowest fullerene triplet level through sensitized singlet oxygen luminescence in the NIR region, it is shown that the final sink of photoinduced processes is always the fullerene triplet. This can be populated via a two-step charge-separation charge-recombination process and a less favored (3)MLCT --> (3)C60 triplet-triplet energy-transfer pathway. In CuFc-F, both of the photoexcited copper(I)-complexed and fullerene moieties are quenched by the presence of the ferrocene unit, most likely via ultrafast energy transfer.     

Fluorescent macrocyclic chemosensor for Zn(II) detection at alkaline pH values

ABSTRACT

The new macrocyclic ligand L (28,29-dimethoxy-27-oxa-8,11,14,17,25,26-hexaazatetracyclo[22.2.1.1(2,6).1(19,23)]nonacosa-2,4,6(28),19,21,23(29),24,26(1)-octaene) has been synthesised. It contains a tetramine chain and the 2,5-bis(2-methoxy-3-metyl-phenyl)-1,3,4-oxadiazole (PPD-OMe) chromophore, acting as coordinating and sensing units, respectively.

The fluorescent emission of L depends on the pH being highly fluorescent at pH = 2 and not emitting from pH >10. The studies highlighted that L is a PET mediated emitting chemosensor, being the PET effect regulated by the degree of the tetraamine protonation.

L coordinates metal ions (Cu(II), Zn(II) and Cd(II)) in water giving rise to an OFF-ON fluorescent response for the presence of Zn(II) ion thus signalling its presence in the medium. This response is particularly notable at pH = 9 allowing to extend the Zn(II) sensing also in the alkaline pH field.     

Elastic and dynamical properties of alkali-silicate glasses from computer simulations techniques

This paper shows recent progresses in the field of computer simulations of inorganic glasses. Molecular dynamics simulations and energy minimization methods have been applied to calculate the elastic and transport properties of alkali silicate glasses of compositions xM₂O · (100 ? x)SiO₂ (with x = 0, 10, 15, 20, 25, 30 % mol for M = Li, Na and K) and of a soda-lime glass with composition 15Na₂O · 10CaO · 75SiO₂, which has been employed to ascertain the effect of the replacement of CaO for Na₂O. The excellent agreement of the computed results with the experimental data highlights the important predictive and interpretative role reached by computer simulations techniques.     

Materials for peripheral nerve regeneration

Recent efforts in scientific research in the field of peripheral nerve regeneration have been directed towards the development of artificial nerve guides. We have studied various materials with the aim of obtaining a biocompatible and biodegradable two layer guide for nerve repair. The candidate materials for use as an external layer for the nerve guides were poly(caprolactone) (PCL), a biosynthetic blend between PCL and chitosan (CS) and a synthesised poly(ester-urethane) (PU). Blending PCL, which is a biocompatible synthetic polymer, with a natural polymer enhanced the system biocompatibility and biomimetics, fastened the degradation rates and reduced the production costs. Various novel block poly(ester-urethane)s are being synthesised by our group with tailored properties for specific tissue engineering applications. One of these poly(ester-urethane)s, based on a low molecular weight poly(caprolactone) as the macrodiol, cycloesandimethanol as the chain extender and hexamethylene diisocyanate as the chain linker, was investigated for the production of melt extruded nerve guides. We studied natural polymers such as gelatin (G), poly(L-lysine) (PL) and blends between chitosan and gelatin (CS/G) as internal coatings for nerve guides. In vitro and in vivo tests were performed on PCL guides internally coated either with G or PL to determine the differences in the quality of nerve regeneration associated with the type of adhesion protein. CS/G natural blends combined the good cell adhesion properties of the protein phase with the ability to promote nerve regeneration of the polysaccharide phase. Natural blends were crosslinked both by physical and chemical crosslinking methods. In vitro neuroblast adhesion tests were performed on CS/G film samples, PCL/CS and PU guides internally coated with G to evaluate the ability of such materials towards nerve repair.