Plastic Burning Impacts on Atmospheric Fine Particulate Matter at Urban and Rural Sites in the USA and Bangladesh

To better understand the impact of plastic burning on atmospheric fine particulate matter (PM_2.5), we evaluated two methods for the quantification of 1,3,5-triphenylbenzene (TPB), a molecular tracer of plastic burning. Compared to traditional solvent-extraction gas chromatography mass spectrometry (GCMS) techniques, thermal-desorption (TD) GCMS provided higher throughput, lower limits of detection, more precise spike recoveries, a wider linear quantification range, and reduced solvent use. This method enabled quantification of TPB in fine particulate matter (PM_2.5) samples collected at rural and urban sites in the USA and Bangladesh. These analyses demonstrated a measurable impact of plastic burning at 5 of the 6 study locations, with the largest absolute and relative TPB concentrations occurring in Dhaka, Bangladesh, where plastic burning is expected to be a significant source of PM_2.5. Background-level contributions of plastic burning in the USA were estimated to be 0.004-0.03 μg m^-3 of PM_2.5 mass. Across the four sites in the USA, the lower estimate of plastic burning contributions to PM_2.5 ranged 0.04-0.8%, while the median estimate ranged 0.3-3% (save for Atlanta, Georgia, in the wintertime at 2-7%). The results demonstrate a consistent presence of plastic burning emissions in ambient PM_2.5 across urban and rural sites in the USA, with a relatively small impact in comparison to other anthropogenic combustion sources in most cases. Much higher TPB concentrations were observed in Dhaka, with estimated plastic burning impacts on PM_2.5 ranging from a lower estimate of 0.3-1.8 μg m^-3 (0.6-2% of PM_2.5) and the median estimate ranging 2-35 μg m^-3 (5-15% of PM_2.5). The methodological advances and new measurements presented herein help to assess the air quality impacts of burning plastic more broadly.

Blue Emitting Star-Shaped and Octasilsesquioxane-Based Polyanions Bearing Boron Clusters. Photophysical and Thermal Properties

High boron content systems were prepared by the peripheral functionalisation of 1,3,5-triphenylbenzene (TPB) and octavinylsilsesquioxane (OVS) with two different anionic boron clusters: closo-dodecaborate (B12) and cobaltabisdicarbollide (COSAN). TPB was successfully decorated with three cluster units by an oxonium ring-opening reaction, while OVS was bonded to eight clusters by catalysed metathesis cross-coupling. The resulting compounds were spectroscopically characterised, and their solution-state photophysical properties analysed. For TPB, the presence of COSAN dramatically quenches the fluorescence emission (λem = 369 nm; ΦF = 0.8%), while B12-substituted TPB shows an appreciable emission efficiency (λem = 394 nm; ΦF = 12.8%). For octasilsesquioxanes, the presence of either COSAN or B12 seems to be responsible for ∼80 nm bathochromic shift with respect to the core emission, but both cases show low emission fluorescence (ΦF = 1.4-1.8%). In addition, a remarkable improvement of the thermal stability of OVS was observed after its functionalisation with these boron clusters.

Identification of Novel 1,3,5-Triphenylbenzene Derivative Compounds as Inhibitors of Hen Lysozyme Amyloid Fibril Formation

Deposition of soluble proteins as insoluble amyloid fibrils is associated with a number of pathological states. There is a growing interest in the identification of small molecules that can prevent proteins from undergoing amyloid fibril formation. In the present study, a series of small aromatic compounds with different substitutions of 1,3,5-triphenylbenzene have been synthesized and their possible effects on amyloid fibril formation by hen egg white lysozyme (HEWL), a model protein for amyloid formation, and of their resulting toxicity were examined. The inhibitory effect of the compounds against HEWL amyloid formation was analyzed using thioflavin T and Congo red binding assays, atomic force microscopy, Fourier-transform infrared spectroscopy, and cytotoxicity assays, such as the 3-(4,5-Dimethylthiazol)-2,5-Diphenyltetrazolium Bromide (MTT) reduction assay and caspase-3 activity measurements. We found that all compounds in our screen were efficient inhibitors of HEWL fibril formation and their associated toxicity. We showed that electron-withdrawing substituents such as –F and –NO₂ potentiated the inhibitory potential of 1,3,5-triphenylbenzene, whereas electron-donating groups such as –OH, –OCH₃, and –CH₃ lowered it. These results may ultimately find applications in the development of potential inhibitors against amyloid fibril formation and its biologically adverse effects.