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Catechol (1,2-benzenediol), a common phenolic species emitted during biomass burning, is both redox active and metal chelating. When oxidized by OH radicals in the aqueous phase, it rapidly forms brown carbon (BrC). Here, we report chamber studies of the multiphase chemistry of catechol using HOOH as an OH radical source, soluble iron, simulated sunlight, and either deliquesced or solid-phase seed particles. BrC of remarkable similarity (MAC365 = 1.7 ±0.2 m2 g-1, “medium-BrC” category) was produced whenever gas-phase catechol was photolyzed in the chamber, with or without the presence of an OH radical source, soluble iron, or deliquesced aerosol. The speed and quantity of BrC formation varied, however. While BrC production was slower in the absence of an OH radical source, multiple lines of evidence suggest that OH generation via photosensitization by surface-adsorbed catechol can still generate BrC. Fenton chemistry actively occurred in surface-adsorbed water layers even below the seed particle deliquescence point, leading to significant production of gas-phase benzoquinone. Ratios of BrC and secondary organic aerosol (SOA) relative to catechol concentrations were highest in the presence of trace amounts of soluble iron, HOOH, and simulated sunlight, indicating that photo-Fenton chemistry contributed substantially to BrC and SOA formation by catechol. Finally, we observed that BrC and SOA formation by catechol / photo-Fenton chemistry can occur efficiently even at 40% RH. These results are consistent with catechol being a major source of secondary BrC in biomass burning plumes, even at moderate relative humidity. 

Guaiacol, present in wood smoke, readily forms secondary organic aerosol (SOA), and, in the aqueous phase, brown carbon (BrC) species. Here, BrC is produced in an illuminated chamber containing guaiacol(g), HOOH(g) as an OH radical source, and either deliquesced salt particles or guaiacol SOA at 50% relative humidity. BrC production slows without an OH source (HOOH), likely due to low levels of radical generation by photosensitization, perhaps involving surface-adsorbed guaiacol and dissolved oxygen. With or without HOOH, BrC mass absorption coefficients at 365 nm generated by the guaiacol + OH reaction reach a maximum at ~6 h of atmospheric OH exposure, after which photobleaching becomes dominant. In the presence of soluble iron but no HOOH, more BrC is produced, likely due to insoluble polymer production observed in previous studies. However, with both soluble iron and HOOH (enabling Fenton chemistry), significantly less SOA and BrC are produced due to very high oxidation rates, and the average SOA carbon oxidation state reaches 2, indicating carboxylate products like oxalate. These results indicate that SOA and BrC formation by guaiacol photooxidation can take place over a wider range of atmospheric conditions than previously thought, and that the effects of iron(II) depend on HOOH. Multiphase guaiacol photooxidation likely makes a significant contribution to producing highly oxidized SOA material in smoke plumes. 

A method is provided for using twisted acenes, and more particularly to configurationally stable twisted acenes that are imbedded into the structure of [7]helicene at the fulcrum ring to form useable material structures. The helicene propa- gates its chiral nature into the acene, while acting as a locking mechanism to thermal racemization. These doubly- helical compounds are part of a new homologous series of polycyclic aromatic hydrocarbons, namely the [7]helitwis- tacenes. Such [7]helitwistacenes have utility as materials suitable for forming a circularly polarized organic light emitting diode (CP-OLED) for direct emission of circularly polarized (CP) light for the fabrication of high efficiency electronic displays. 

Although catenanes comprising two ring-shaped components can be made in large quantities by templation, the preparation of three-dimensional (3D) catenanes with cage-shaped components is still in its infancy. Here, we report the design and syntheses of two 3D catenanes by a sequence of S N 2 reactions in one pot. The resulting triply mechanically interlocked molecules were fully characterized in both the solution and solid states. Mechanistic studies have revealed that a suit[3]ane, which contains a threefold symmetric cage component as the suit and a tribromide component as the body, is formed at elevated temperatures. This suit[3]ane was identified as the key reactive intermediate for the selective formation of the two 3D catenanes which do not represent thermodynamic minima. We foresee a future in which this particular synthetic strategy guides the rational design and production of mechanically interlocked molecules under kinetic control. 

Abstract Iron is essential to life, but surprisingly little is known about how iron is managed in nonvertebrate animals. In mammals, the well‐characterizedtransferrinsbind iron and are involved in iron transport or immunity, whereas other members of thetransferrinfamily do not have a role in iron homeostasis. In insects, the functions oftransferrinsare still poorly understood. The goals of this project were to identify thetransferringenes in a diverse set of insect species, resolve the evolutionary relationships among these genes, and predict which of thetransferrinsare likely to have a role in iron homeostasis. Our phylogenetic analysis oftransferrinsfrom 16 orders of insects and two orders of noninsect hexapods demonstrated that there are four orthologous groups of insecttransferrins. Our analysis suggests thattransferrin 2arose prior to the origin of insects, andtransferrins 1,3, and4arose early in insect evolution. Primary sequence analysis of each of the insecttransferrinswas used to predict signal peptides, carboxyl‐terminal transmembrane regions, GPI‐anchors, and iron binding. Based on this analysis, we suggest thattransferrins 2,3, and4are unlikely to play a major role in iron homeostasis. In contrast, thetransferrin 1orthologs are predicted to be secreted, soluble, iron‐binding proteins. We conclude thattransferrin 1orthologs are the most likely to play an important role in iron homeostasis. Interestingly, it appears that the louse, aphid, and thrips lineages have lost thetransferrin 1gene and, thus, have evolved to manage iron withouttransferrins.