Site selective reading of epigenetic markers by a dual-mode synthetic receptor array.

Variably functionalized self-folding deep cavitands form an arrayed, fluorescent indicator displacement assay system for the detection of post-translationally modified (PTM) histone peptides. The hosts bind trimethyllysine (KMe3) groups, and use secondary upper rim interactions to provide more sensitive discrimination between targets with identical KMe3 binding handles. The sensor array uses multiple different recognition modes to distinguish between miniscule differences in target, such as identical lysine modifications at different sites of histone peptides. In addition, the sensor is affected by global changes in structure, so it is capable of discriminating between identical PTMs, at identical positions on amino acid fragments that vary only in peptide backbone length, and can be applied to detect non-methylation modifications such as acetylation and phosphorylations located multiple residues away from the targeted binding site. The synergistic application of multiple variables allows dual-mode deep cavitands to approach levels of recognition selectivity usually only seen with antibodies

Using light intensity to control reaction kinetics and reversibility in photomechanical crystals.

4-Fluoro-9-anthracenecarboxylic acid (4F-9AC) is a thermally reversible (T-type) photomechanical molecular crystal. The photomechanical response is driven by a [4 + 4] photodimerization reaction, while the photodimer dissociation determines the reset time. In this paper, both the chemical kinetics of dimer dissociation (using a microscopic fluorescence-recovery-after-photobleaching experiment) and mechanical reset dynamics (by imaging bending microneedles) for single 4F-9AC crystals are measured. The dissociation kinetics depend strongly on the initial concentration of photodimer, slowing down and becoming nonexponential at high dimer concentrations. This dose-dependent behavior is also observed in the mechanical response of bending microneedles. A new feature in the photomechanical behavior is identified: the ability of a very weak control beam to suppress dimer dissociation after large initial dimer conversions. This phenomenon provides a way to optically control the mechanical response of this photomechanical crystal. To gain physical insight into the origin of the nonexponential recovery curves, the experimental results are analyzed in terms of a standard first-order kinetic model and a nonlinear Finke-Watzky (FW) model. The FW model can qualitatively reproduce the transition from exponential to sigmoidal recovery with larger initial conversions, but neither model can reproduce the suppression of the recovery in the presence of a weak holding beam. These results highlight the need for more sophisticated theories to describe cooperative phenomena in solid-state crystalline reactions, as well as demonstrating how this behavior could lead to new properties and/or improved performance in photomechanical materials

Effect of halogen substitution on energies and dynamics of reversible photomechanical crystals based on 9-anthracenecarboxylic acid

9-Anthracene carboxylic acid derivatives comprise a family of thermally reversible photomechanical molecular crystals. The photomechanical response relies on a [4 + 4] photodimerization followed by dissociation that occurs on timescales of seconds to minutes. A combined theoretical and experimental investigation is undertaken to better understand how chemical modification of the anthracene core influences energetics of both the isolated molecule and the crystal lattice. We use both density functional theory and dispersion-corrected Moller–Plesset perturbation theory computational methods to establish orbital energies, photodimerization reaction energies, and lattice energies for a set of substituted 9-anthracene carboxylic acid molecules. The calculations reveal that steric interactions play a dominant role in the ability to form photodimers and indicate an energetic threshold of 80–90 kJ per mole for the dimerization reaction. Examination of intermolecular bonding in a subset of fluorinated 9ACs revealed the absence of H⋯F intermolecular bond formation and energy differences that can explain observed trends in the dissociation kinetics and mechanical reset times. Fluorescence recovery after photobleaching experiments shows that the photodimer dissociation kinetics depend on the amount of initial photodimer, preventing a straightforward correlation between halogen atom substitution and dissociation rates using the Bell–Evans–Polanyi principle. The results clarify how molecular structure affects intermolecular interactions and photoreactivity in this family of molecular crystals, but the origin of the complex photodimer dissociation dynamics remains an open question

Boosting the Heavy Atom Effect by Cavitand Encapsulation: Room Temperature Phosphorescence of Pyrene in the Presence of Oxygen

A deep cavitand is used to encapsulate the aromatic molecule pyrene in its interior while also binding Tl⁺ ions with its terminal carboxylates. Steady-state and time-resolved spectroscopic experiments, along with quantum yield measurements, quantify the enhancements of intersystem crossing and room temperature phosphorescence due to cavitand encapsulation. These results are compared to those obtained for pyrene contained in sodium dodecyl sulfate micelles, which is the usual system used to generate room temperature phosphorescence. The combination of selective binding and strong Tl⁺ recognition by the cavitand enhances the intersystem crossing and decreases the phosphorescence radiative lifetime from ∼30 to 0.23 s. The cavitand also decreases the rate of O₂ quenching by a factor of 100. Together, these factors can boost the room temperature phosphorescence signal by several orders of magnitude, allowing it to be detected in water without O₂ removal. Host:guest recognition provides a route to molecular-scale triplet emitters that can function under ambient conditions

Self-Aggregating Deep Cavitand Acts as a Fluorescence Displacement Sensor for Lysine Methylation

A dual-mode aggregative host:guest indicator displacement sensing system has been created for the detection of trimethylated peptides and determination of histone demethylase activity. The combination of selective recognition of suitably sized trimethylammonium salts and reversible lipophilic aggregation of the host:guest complex provides a unique quenching mechanism that is not only dependent on affinity for sensitivity but the lipophilicity of the indicator. In addition, aggregation can be controlled by the application of chaotropic anions in the mixture, allowing a second level of discrimination between hard lysine groups and softer trimethyllysines

Accounting Anomalies and Fundamental Analysis: A Review of Recent Research Advances

We survey recent research in accounting anomalies and fundamental analysis. We use forecasting of future earnings and returns as our organizing framework and suggest a roadmap for research aiming to document the forecasting benefits of accounting information. We combine this with opinions from the academic and practitioner communities to critically evaluate key clusters of papers about accounting anomalies and fundamental analysis disseminated over the last decade. Finally, we provide a new analysis on how an ex ante and ex post treatment of risk and transaction costs affects the accrual and PEAD anomalies, and offer suggestions for future research