Mechanisms of antioxidant action: Chemical binding of a thiol antioxidant into polypropylene by means of uv irradiation

3,5-Di-t-butyl-4-hydroxybenzyl mercaptan (BHBM) became chemically combined to polypropylene to the extent of 68% of the antioxidant present when films containing BHBM were exposed to uv irradiation. In addition to the radical coupling reaction of the thiyl radical derived from BHBM with the polymer, a second technologically less useful process also occurs, leading to the formation of a derived stilbenequinone. The latter absorbs strongly both in the visible and in the near uv and consequently slows down the subsequent loss of the bound antioxidant from the polymer.     

PRODUCTS OF CHLOROPHYLL PHOTODEGRADATION–2. STRUCTURAL IDENTIFICATION

Abstract— Hydrophilic products of chlorophyll a photodegradation are structurally identified using UV/visible and fourier transform infrared spectrophotometry and gas chromatography-mass spectrometry. The major peak detected during reverse-phase high performance liquid chromatography of the colourless photodegradation products is identified as glycerol. Lactic, citric, succinic and malonic acids, as well as alanine, are also identified.     

Mechanisms of antioxidant action: Synergism between a 2-hydroxybenzophenone uv stabiliser and autosynergistic antioxidants in polypropylene

Synergism between a uv stabiliser (2-hydroxy-4-octoxybenzophenone (I)) and phenolic antioxidants has been studied during the photo-oxidation of polypropylene. It has been found that hindered phenols containing benzylic sulphur (II) are more effective synergists at the same molar concentration than conventional hindered phenols and that optimum synergism occurs at high molar ratios (I/II). The autosynergistic phenols (II) are shown to protect the uv stabiliser against the effects of hydroperoxides under photo-oxidative conditions by catalytically destroying them and scavenging radicals formed from them. The ‘uv absorber’ (I) also appears to deactivate excited species formed in the photo-decomposition of oxidation products of (II).     

Mechanisms of antioxidant action: Effect of processing on the behaviour of hindered phenols in polypropylene

It is shown that in the case of two hindered phenol antioxidants (I R = H and II) products are formed which are considerably more effective than the phenols themselves. Both dimeric products and polymer-bound antioxidants contribute to this effect but the former is considered to be more important under the conditions examined.     

A novel amperometric glucose biosensor based on poly(glycidyl methacrylate-co-(3-thienylmethylmethacrylate))

Two novel glucose oxidase (GOx) enzyme electrodes based on the copolymer of glycidyl methacrylate with 3-thienylmethyl methacrylate (poly(GMA-co-MTM)) with and without polypyrrole (PPyr) coating were prepared and employed in the amperometric determination of glucose levels. The effect of PPyr coating on the electrode properties was investigated in detail. Cyclic voltammetry studies showed that electrical conductivity of electrode B with PPyr coating (poly(GMA-co-MTM)/GOx/PPyr) was substantially higher than that of electrode A (poly(GMA-co-MTM)/GOx). On the other hand, electrode A showed better results in terms of sensitivity (10 nA/mM), limit of detection (50.2 μM), and response time (5 s). Electrodes A and B gave linear responses to the glucose concentrations in the range of 2–20 and 2–14 mM, respectively. The ranges of linearity for both enzyme electrodes are sufficient for the determination of physiological glucose concentrations in human blood. Moreover, PPyr coating of electrode B did not result in further stabilization of the enzyme electrode.     

Evaluating Feasibility of Human Tissue Engineered Respiratory Epithelium Construct as a Potential Model for Tracheal Mucosal Reconstruction

The normal function of the airway epithelium is vital for the host’s well-being. Conditions that might compromise the structure and functionality of the airway epithelium include congenital tracheal anomalies, infection, trauma and post-intubation injuries. Recently, the onset of COVID-19 and its complications in managing respiratory failure further intensified the need for tracheal tissue replacement. Thus far, plenty of naturally derived, synthetic or allogeneic materials have been studied for their applicability in tracheal tissue replacement. However, a reliable tracheal replacement material is missing. Therefore, this study used a tissue engineering approach for constructing tracheal tissue. Human respiratory epithelial cells (RECs) were isolated from nasal turbinate, and the cells were incorporated into a calcium chloride-polymerized human blood plasma to form a human tissue respiratory epithelial construct (HTREC). The quality of HTREC in vitro, focusing on the cellular proliferation, differentiation and distribution of the RECs, was examined using histological, gene expression and immunocytochemical analysis. Histological analysis showed a homogenous distribution of RECs within the HTREC, with increased proliferation of the residing RECs within 4 days of investigation. Gene expression analysis revealed a significant increase (p < 0.05) in gene expression level of proliferative and respiratory epithelial-specific markers Ki67 and MUC5B, respectively, within 4 days of investigation. Immunohistochemical analysis also confirmed the expression of Ki67 and MUC5AC markers in residing RECs within the HTREC. The findings show that calcium chloride-polymerized human blood plasma is a suitable material, which supports viability, proliferation and mucin secreting phenotype of RECs, and this suggests that HTREC can be a potential candidate for respiratory epithelial tissue reconstruction.     

Oxy-Polybrominated Diphenyl Ethers from the Indonesian Marine Sponge,Lamellodysidea herbacea: X-ray,SAR, and Computational Studies

Polybrominated diphenyl ether (PBDE) compounds, derived from marine organisms, originate from symbiosis between marine sponges and cyanobacteria or bacteria. PBDEs have broad biological spectra; therefore, we analyzed structure and activity relationships of PBDEs to determine their potential as anticancer or antibacterial lead structures, through reactions and computational studies. Six known PBDEs (1–6) were isolated from the sponge, Lamellodysdiea herbacea; ¹³C NMR data for compound 6 are reported for the first time and their assignments are confirmed by their theoretical ¹³C NMR chemical shifts (RMSE < 4.0 ppm). Methylation and acetylation of 1 (2, 3, 4, 5-tetrabromo-6-(3′, 5′-dibromo-2′-hydroxyphenoxy) phenol) at the phenol functional group gave seven molecules (7–13), of which 10, 12, and 13 were new. New crystal structures for 8 and 9 are also reported. Debromination carried out on 1 produced nine compounds (1, 2, 14, 16–18, 20, 23, and 26) of which 18 was new. Debromination product 16 showed a significant IC₅₀ 8.65 ± 1.11; 8.11 ± 1.43 µM against human embryonic kidney (HEK293T) cells. Compounds 1 and 16 exhibited antibacterial activity against Gram-positive Staphylococcus aureus and Gram-negative Klebsiella pneumoniae with MID 0.078 µg/disk. The number of four bromine atoms and two phenol functional groups are important for antibacterial activity (S. aureus and K. pneumoniae) and cytotoxicity (HEK293T). The result was supported by analysis of frontier molecular orbitals (FMOs). We also propose possible products of acetylation and debromination using analysis of FMOs and electrostatic charges and we confirm the experimental result.     

1,1,2-Trihaloalkenes and Dimeric Acetylenes from Acetylenic Tellurium Species

Reaction of 1-teliuroalk-1-ynes with bromine and iodine or with Cu(II) chloride furnishes respectively 1,1,2-trihaloalkcnes and 1,4-disubstituted 1,3-diynes.