Abstract Intramolecular alkene‐arene meta ‐photocycloadditions are powerful transformations that use the enhanced reactivity of photoexcited benzene rings to facilitate addition of an alkene 1,3 across donor groups and form complex three‐dimensional fused‐ring systems from readily accessible starting materials. Intramolecular examples have traditionally been restricted to three‐membered tethers, with cycloaddition resulting from exo ‐conformation. However, by judicious tether design we have demonstrated that a four‐membered tether can also proceed in good yield; interestingly, via an endo exciplex (1.2 : 1) enabling access to both natural product skeletons and interesting scaffolds for medicinal chemistry research.
TNF-alpha is an inflammatory cytokine produced by B cells that also impacts B cell differentiation and Ig secretion. We have investigated the regulation of the TNF-alpha gene in a human B cell line in response to platelet-activating factor (PAF), a potent phospholipid often produced in inflammatory reactions. We report here that PAF increases the RNA levels for the TNF-alpha gene in the human B cell line Ramos. This is mediated by an increase in the transcription rate and a longer half-life of the TNF-alpha transcripts. Induction of the TNF-alpha gene is rapid in these cells and independent of new protein synthesis. Despite increasing RNA for the TNF-alpha gene, PAF increases TNF-alpha protein levels only in the presence of a costimulus, such as PMA. We hypothesize that PAF acts at the transcriptional level to increase TNF-alpha RNA, but a post-transcriptional block acts to regulate protein production. We also report that PAF enhances PMA-induced TNF-alpha production from human peripheral B cells. This increase is maximal at 0.1 microM PAF and is blocked by PAF receptor antagonists. The ability of PAF to modulate cytokine production from human B cells provides further evidence that PAF has a role in B cell biology and suggests it may be important in conditions involving B cell-derived cytokines.
Using a combination of liquid-phase X-ray spectroscopy experiments and small-scale calculations we have gained new insights into the speciation of halozincate anions in ionic liquids.
Using a combination of experiments and calculations, we have gained new insights into the nature of anion–cation interactions in ionic liquids (ILs). An X-ray photoelectron spectroscopy (XPS)-derived anion-dependent electrostatic interaction strength scale, determined using XPS core-level binding energies for IL cations, is presented here for 39 different anions, with at least 18 new anions included. Linear correlations of experimental XPS core-level binding energies for IL cations with (a) calculated core binding energies (ab initio molecular dynamics (AIMD) simulations were used to generate high-quality model IL structures followed by single-point density functional theory (DFT) to obtain calculated core binding energies), (b) experimental XPS core-level binding energies for IL anions, and (c) other anion-dependent interaction strength scales led to three main conclusions. First, the effect of different anions on the cation can be related to ground-state interactions. Second, the variations of anion-dependent interactions with the identity of the anion are best rationalized in terms of electrostatic interactions and not occupied valence state/unoccupied valence state interactions or polarizability-driven interactions. Therefore, the XPS-derived anion-dependent interaction strength scale can be explained using a simple electrostatic model based on electrostatic site potentials. Third, anion–probe interactions, irrespective of the identity of the probe, are primarily electrostatic, meaning that our electrostatic interaction strength scale captures some inherent, intrinsic property of anions independent of the probe used to measure the interaction strength scale.
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