Degradable Elastomers: Is There a Future in Tyre Compound Formulation?

Problems related to non-biodegradable waste coming from vulcanized rubber represent one of the pre-eminent challenges for modern society. End-of-life tyres are an important source of this typology of waste and the increasingly high accumulation in the environment has contributed over the years to enhance land and water pollution. Moreover, the release into the environment of non-degradable micro-plastics and other chemicals as an effect of tyre abrasion is not negligible. Many solutions are currently applied to reuse end-of-life tyres as a raw material resource, such as pyrolysis, thermo-mechanical or chemical de-vulcanisation, and finally crumbing trough different technologies. An interesting approach to reduce the environmental impact of vulcanised rubber wastes is represented by the use of degradable thermoplastic elastomers (TPEs) in tyre compounds. In this thematic review, after a reviewing fossil fuel-based TPEs, an overview of the promising use of degradable TPEs in compound formulation for the tyre industry is presented. Specifically, after describing the properties of degradable elastomers that are favourable for tyres application in comparison to used ones, the real scenario and future perspectives related to the use of degradable polymers for new tyre compounds will be realized.     

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.     

Gas-phase doubly charged complexes of cyclic peptides with copper in +1, +2 and +3 formal oxidation states: formation, structures and electron capture dissociation

Copper complexes with a cyclic D-His-β-Ala-L-His-L-Lys and all-L-His-β-Ala-His-Lys peptides were generated by electrospray which were doubly charged ions that had different formal oxidation states of Cu(I), Cu(II) and Cu(III) and different protonation states of the peptide ligands. Electron capture dissociation showed no substantial differences between the D-His and L-His complexes. All complexes underwent peptide cross-ring cleavages upon electron capture. The modes of ring cleavage depended on the formal oxidation state of the Cu ion and peptide protonation. Density functional theory (DFT) calculations, using the B3LYP with an effective core potential at Cu and M06-2X functionals, identified several precursor ion structures in which the Cu ion was threecoordinated to pentacoordinated by the His and Lys side-chain groups and the peptide amide or enolimine groups. The electronic structure of the formally Cu(III) complexes pointed to an effective Cu(I) oxidation state with the other charge residing in the peptide ligand. The relative energies of isomeric complexes of the [Cu(c-HAHK + H)](2+) and [Cu(c-HAHK - H)](2+) type with closed electronic shells followed similar orders when treated by the B3LYP and M06-2X functionals. Large differences between relative energies calculated by these methods were obtained for open-shell complexes of the [Cu(c-HAHK)](2+) type. Charge reduction resulted in lowering the coordination numbers for some Cu complexes that depended on the singlet or triplet spin state being formed. For [Cu(c-HAHK - H)](2+) complexes, solution H/D exchange involved only the N-H protons, resulting in the exchange of up to seven protons, as established by ultra-high mass resolution measurements. Contrasting the experiments, DFT calculations found the lowest energy structures for the gas-phase ions that were deprotonated at the peptide C(α) positions.     

On some Fano manifolds of large pseudoindex

In this paper we classify pairs (X,ℰ) with ℰ ample vector bundle of rank r on a smooth variety X of dimension n= 2r−1 such that K _X + det ℰ=? _x . Received: 7 April 2000     

Characterization and differentiation of heterocyclic isomers. Part 3. Study of high internal energy ions produced by electron ionization mass spectrometry on 3-methyl-1,2- and 2-methyl-1,3-thiazolopyridines

The eight members of two classes of heterocyclic isomers, namely 3-methyl-1,2-, 1a-d and 2-methyl-1,3-thiazolopyridines 2a-d have been characterized by mass spectrometry under electron ionization. High internal energy ions formed in the source have been studied by low and high resolution mass spectrometry. The data show remarkable differences among the various components of each class depending on the position of the nitrogen in the pyridine ring. Furthermore, by comparing the mass spectra of members of series 1 with those of their corresponding isomers belonging to series 2 , it is still possible to obtain evidence for different behaviors in the fragmentation pathways. It seems to exclude the occurrence of inter-conversion phenomena from one isomer into another, as well as conversion to a common intermediate before fragmentation. This also suggests that each member of series 1 and 2 retains its own structure after electron ionization. The data obtained on a double focusing instrument equipped with electrostatic and magnetic analyzers have been compared with those obtained on a mass spectrometer with an ion trap as the analyzer.     

New Histamine-Related Five-Membered N-Heterocycle Derivatives as Carbonic Anhydrase I Activators

A series of histamine (HST)-related compounds were synthesized and tested for their activating properties on five physiologically relevant human Carbonic Anhydrase (hCA) isoforms (I, II, Va, VII and XIII). The imidazole ring of HST was replaced with different 5-membered heterocycles and the length of the aliphatic chain was varied. For the most interesting compounds some modifications on the terminal amino group were also performed. The most sensitive isoform to activation was hCA I (K_A values in the low micromolar range), but surprisingly none of the new compounds displayed activity on hCA II. Some derivatives (1, 3a and 22) displayed an interesting selectivity for activating hCA I over hCA II, Va, VII and XIII.     

Modelling of Enzyme Properties in Organic Solvents

 In this article we review how molecular modeling techniques can be used to shed some light on the influence of organic solvents on the molecular characteristics of proteins and enzymes. Molecular dynamic simulations on bovine pancreas trypsin inhibitor, chymotrypsin, and subtilisin make it possible to get a deeper understanding into how increased intramolecular interactions improve conformational rigidity, thus explaining the lower reactivity and the higher thermostability of enzymes in non-aqueous media. The application of thermodynamics-based models allows first qualitative predictions on the selectivity of many reaction types; however, the application of quantum mechanical/molecular mechanical methods is required for the development of quantitative models of actual reactivity patterns.     

Characterization of additives in plastics: From MS to MS10 multistep mass analysis and theoretical calculations of tris(2,4‐di‐tert‐butylphenyl)phosphate

In the analysis by electrospray (+) of an extract of hemp sprouts put in a polypropylene vial, we found a large contamination of a plastic additive. It was characterized by multiple‐stage MSⁿ experiments (MS ÷ MS¹⁰) and identified as tris(2,4‐di‐tert‐butylphenyl)phosphate, also known with the synonyms F32IRS6B46, oxidized Naugard 524, and others. The MS² ÷ MS⁷ spectra are characterized by consecutive eliminations of six isobutene molecules from the tert‐butyl moieties, some of them also occurring in the ion source. The first three are calculated to occur preferentially from the ortho positions, whereas eliminations from the para positions are estimated to be less favored at about 5–6 kcal/mol in each step. Once the first three isobutene molecules are eliminated, the remaining three are lost from the tert‐butyl moieties in para positions (MS⁵ ÷ MS⁷), yielding protonated triphenylphosphate, whose structure has been confirmed by the MS² spectrum of triphenylphosphate standard: the latter spectrum is almost superimposable with the MS⁸ spectrum of the analyte under investigation. MS⁸ and MS⁹ spectra show main losses of water and C₆H₄ molecules. The MS¹⁰ spectrum of precursor ions at m/z 215 shows the gas‐phase addition of water and methanol and ions at m/z 168, attributable to the loss of a phosphorus oxide radical. Density functional theory (DFT) calculations (Becke 3LYP [B3LYP] 6‐311+G(2d,2p)) have been used to evaluate structure and stability of different ionic and neutral species involved in the decomposition pathways and to calculate thermochemical data of the decomposition reactions. This multistep mass analysis combined with theoretical calculations resulted to be particularly useful and effective, yielding chemical, thermochemical, and mechanistic data of significant utility in the structural characterization and identification of the unknown analyte as well as to define its gas‐phase reactivity under a multistep low‐energy collision‐induced dissociation regime.