The Effect of the Ionizing Radiation on Hydroxyapatite–Polydimethylsiloxane Layers

The bio hydroxyapatite (HAp) was used from a long time in different medical and environmental applications. The HAp layers with a uniform surface were used for various medical applications such as orthopedic and dental metal implants. In this work, we reported on the influence of X‐ray radiation on the structural and morphological properties of composite layers based on HAp and polydimethylsiloxane (PDMS) deposited on titanium substrates. The HAp:PDMS layers were investigated by different complementary methods such as scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and glow discharge optical emission spectrometry (GDOES). FTIR spectral analysis showed that the molecular structure of the coatings was not changed after their irradiation even though, the depth profile analysis performed by GDOES indicated a depletion of Ca and P elements from the HAp:PDMS irradiated samples. By SEM, we showed that the morphological features of the coatings were also changed, as the irradiated layers are delaminated. The biological assays confirmed that the antibacterial activity of HAp:PDMS composite layers increased after irradiation. The results obtained in this study highlighted that the biological properties of HAp:PDMS layers could be influenced by irradiation. POLYM. ENG. SCI., 59:2406–2412, 2019. © 2019 Society of Plastics Engineers     

Bioactive Phytochemicals from Wild Arbutus unedo L. Berries from Different Locations in Portugal: Quantification of Lipophilic Components

The lipophilic composition of wild Arbutus unedo L. berries, collected from six locations in Penacova (center of Portugal), as well as some general chemical parameters, namely total soluble solids, pH, titratable acidity, total phenolic content and antioxidant activity was studied in detail to better understand its potential as a source of bioactive compounds. The chemical composition of the lipophilic extracts, focused on the fatty acids, triterpenoids, sterols, long chain aliphatic alcohols and tocopherols, was investigated by gas chromatography–mass spectrometry (GC–MS) analysis of the dichloromethane extracts. The lipophilic extractives of the ripe A. unedo berries ranged from 0.72% to 1.66% (w/w of dry weight), and consisted mainly of triterpenoids, fatty acids and sterols. Minor amounts of long chain aliphatic alcohols and tocopherols were also identified. Forty-one compounds were identified and among these, ursolic acid, lupeol, α-amyrin, linoleic and α-linolenic acids, and β-sitosterol were highlighted as the major components. To the best of our knowledge the current research study provides the most detailed phytochemical repository for the lipophilic composition of A. unedo, and offers valuable information for future valuation and exploitation of these berries.     

Evolutionary Imprint of Catalytic Domains in Fungal PKS–NRPS Hybrids

Fungal hybrid enzymes consisting of a polyketide synthase (PKS) and a nonribosomal peptide synthetase (NRPS) module are involved in the biosynthesis of a vast array of ecologically and medicinally relevant natural products. Whereas a dozen gene clusters could be assigned to the requisite PKS–NRPS pathways, the programming of the multifunctional enzymes is still enigmatic. Through engineering and heterologously expressing a chimera of PKS (lovastatin synthase, LovB) and NRPS (cytochalasin synthase, CheA) in Aspergillus terreus, we noted the potential incompatibility of a fungal highly reducing PKS (hrPKS) with the NRPS component of fungal PKS–NRPS hybrids. To rationalize the unexpected outcome of the gene fusion experiments, we conducted extensive bioinformatic analyses of fungal PKS–NRPS hybrids and LovB‐type PKS. From motif studies and the function of the engineered chimeras, a noncanonical function of C‐terminal condensation (C) domains in truncated PKS–NRPS homologues was inferred. More importantly, sequence alignments and phylogenetic trees revealed an evolutionary imprint of the PKS–NRPS domains, which reflect the evolutionary history of the entire megasynthase. Furthermore, a detailed investigation of C and adenylation (A) domains provides support for a scenario in which not only the A domain but also the C domain participates in amino acid selection. These findings shed new light on the complex code of this emerging class of multifunctional enzymes and will greatly facilitate future combinatorial biosynthesis and pathway engineering approaches towards natural product analogues.     

Crosslinking and grafting ethylene vinyl acetate copolymer with accelerated electrons in the presence of polyfunctional monomers

In this study, we have studied the effects of polyfunctional monomers (PFMs) on physical properties of ethylene vinyl acetate (EVA) copolymer crosslinked with electron beam (EB) or peroxides. The PFMs used were triallylcyanurate, triallylisocyanurate, trimethylolpropane trimethacrylate, zinc diacrylate, and ethylene glycol dimethacrylate. Using PFMs has led to (1) optimum cure time t ₉₀ decrease from 19′25″ to 17′30″–18′45″, (2) scorch time increase from 2′ to maximum 3′45″, (3) increasing the crosslink density of peroxide or EB-cured systems by increasing the efficiency of productive radical reactions. The most efficient PFM for EVA copolymer blends has been triallylisocyanurate. Tensile strength and tear strength of samples crosslinked with EB for all irradiation doses are significantly better than those obtained for samples crosslinked with peroxides (differences up to 190%). The results show that EB irradiation gave the best results     

Homogeneous nucleation and mesophase formation in glassy isotactic polypropylene

Differential fast scanning chip calorimetry has been employed to study nucleation/ordering during annealing the glass of quenched isotactic polypropylene. Initially non-ordered samples were annealed below the glass transition temperature for different periods of time, and the change of structure during isothermal annealing was then analyzed by monitoring the exchange of latent heat on heating. Primary result of this work is the proof of homogeneous nucleation of ordering and mesophase formation in the glassy state. It is suggested that only local non-cooperative mobility of molecular segments is required to form small, ordered domains, and that the classical nucleation theory, which restricts nucleation of the crystallization/ordering process of polymers to temperatures between the equilibrium melting temperature and the glass transition temperature, needs modification.     

Nanodiamond-mediated crystallization in fibers of PANI nanocomposites produced by template-free polymerization: Conductive and thermal properties of the fibrillar networks

The detonation nanodiamond is a novel versatile nanomaterial with tunable properties and surface chemistry. In this work, we report on a template-free method to synthesize polyaniline based nanocomposite fibers during a chemical oxidative precipitation polymerization where the cooperative interactions between nanodiamond and polyaniline nucleates trigger the final morphology of the nanocomposite. FE–SEM and TEM observations evidence the prominent growth of fibril-like structures assembled in 2-D networks of tightly woven, partially oriented fibers. Optical and Raman spectroscopy and X-ray diffraction analyses reveal that the polymer chains are in a protonated emeraldine form and organize themselves in a highly ordered 3-D spatial arrangement. Conductivity measurements performed on isolated fibers by a conductive tip of an AFM apparatus highlight that the diamond filler does not affect the conductive properties of the polyaniline matrix while increases the thermal stability of the polymer as confirmed by TGA studies.     

Production,Characterization and Synthetic Application of a Purine Nucleoside Phosphorylase from Aeromonas hydrophila

Purine nucleoside phosphorylase (PNP) from Aeromonas hydrophila encoded by the deoD gene has been over‐expressed in Escherichia coli, purified, characterized about its substrate specificity and used for the preparative synthesis of some 6‐substituted purine‐9‐ribosides. Substrate specificity towards natural nucleosides showed that this PNP catalyzes the phosphorolysis of both 6‐oxo‐ and 6‐aminopurine (deoxy)ribonucleosides. A library of nucleoside analogues was synthesized and then submitted to enzymatic phosphorolysis as well. This assay revealed that 1‐, 2‐, 6‐ and 7‐modified nucleosides are accepted as substrates, whereas 8‐substituted nucleosides are not. A few transglycosylation reactions were carried out using 7‐methylguanosine iodide ( 4 ) as a D ‐ribose donor and 6‐substituted purines as acceptor. In particular, following this approach, 2‐amino‐6‐chloropurine‐9‐riboside ( 2c ), 6‐methoxypurine‐9‐riboside ( 2d ) and 2‐amino‐6‐(methylthio)purine‐9‐riboside ( 2g ) were synthesized in very high yield and purity.     

Effects of processing conditions on hybrid filler selective localization,rheological, and thermal properties of poly(ε-caprolactone)/poly(lactic acid) blends

In this study, the effects of processing conditions through different mixing sequences were used to analyze the factors, which could influence the hybrid filler selective localization in an immiscible polymer blend and how localization can influence the rheological and thermal properties. Different selective localizations were observed depending on the mixing sequence used when the hybrid filler was added. Notably, nanoparticles can interact with each other, which favor a synergy between them and alters, besides the localization, the dispersion state, or can interact with one polymer phase, and also alter the nanoparticles' selective localization. An improvement in rheological properties was observed in the hybrid nanocomposite in which there was interaction between the nanoparticles, favoring the hexagonal boron nitride exfoliation. On the other hand, for the storage modulus and degree of crystallinity, the sharpest increase occurred in the hybrid nanocomposite in which the nanoparticles could interact preferably with one polymer phase. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 137, 48711.     

Switching azonaphthols containing a side chain with limited flexibility. Part 1. Synthesis and tautomeric properties

A series of azo dyes, possessing amide fragments with restricted flexibility tethered to 4-(phenyldiazenyl)naphthalen-1-ol, was obtained from 1-hydroxy-2-naphthoic acid by subsequent conversion to amides and diazo coupling. It was shown that the position of the tautomeric equilibrium in solution strongly depends on the solvent in both UV and NMR concentration scale. The compounds exist as pure enol forms in chloroform and hydrocarbons, while in polar solvents (acetone, acetonitrile, alcohols) a tautomeric mixture is observed. According to the quantum-chemical calculations the aggregation of the keto tautomer is the possible reason for this shift in the position of the tautomeric equilibrium. To support the theoretical predictions, it was found that from acetone the keto form crystallizes as a dimer with hydrogen bonding between N₁-H in the one molecule and amide CO in the other forming a three-dimensional structure. The importance of the side-chain nitrogen atom on the dimer formation was confirmed by solution and solid state study of 4-(phenyldiazenyl)-2-acetylnaphthalen-1-ol. The results indicate that the new azo-dyes obtained could be suitable candidates for switching and sensing applications in non-polar solvents.