Synthesis and anticancer activity of epipolythiodiketopiperazine alkaloids

The epipolythiodiketopiperazine (ETP) alkaloids are a highly complex class of natural products with potent anticancer activity. Herein, we report the application of a flexible and scalable synthesis, allowing the construction of dozens of ETP derivatives. The evaluation of these compounds against cancer cell lines in culture allows for the first expansive structure–activity relationship (SAR) to be defined for monomeric and dimeric ETP-containing natural products and their synthetic cognates. Many ETP derivatives demonstrate potent anticancer activity across a broad range of cancer cell lines and kill cancer cells via induction of apoptosis. Several traits that bode well for the translational potential of the ETP class of natural products include concise and efficient synthetic access, potent induction of apoptotic cell death, activity against a wide range of cancer types, and a broad tolerance for modifications at multiple sites that should facilitate small-molecule drug development, mechanistic studies, and evaluation in vivo.National Institute of General Medical Sciences (U.S.) (Grant GM089732)American Society for Engineering Education. National Defense Science and Engineering Graduate FellowshipCamille & Henry Dreyfus Foundation. Teacher-Scholar Awards Progra

Triadin/Junctin Double Null Mouse Reveals a Differential Role for Triadin and Junctin in Anchoring CASQ to the jSR and Regulating Ca2+ Homeostasis

Triadin (Tdn) and Junctin (Jct) are structurally related transmembrane proteins thought to be key mediators of structural and functional interactions between calsequestrin (CASQ) and ryanodine receptor (RyRs) at the junctional sarcoplasmic reticulum (jSR). However, the specific contribution of each protein to the jSR architecture and to excitation-contraction (e-c) coupling has not been fully established. Here, using mouse models lacking either Tdn (Tdn-null), Jct (Jct-null) or both (Tdn/Jct-null), we identify Tdn as the main component of periodically located anchors connecting CASQ to the RyR-bearing jSR membrane. Both proteins proved to be important for the structural organization of jSR cisternae and retention of CASQ within them, but with different degrees of impact. Our results also suggest that the presence of CASQ is responsible for the wide lumen of the jSR cisternae. Using Ca2+ imaging and Ca2+ selective microelectrodes we found that changes in e-c coupling, SR Ca2+content and resting [Ca2+] in Jct, Tdn and Tdn/Jct-null muscles are directly correlated to the effect of each deletion on CASQ content and its organization within the jSR. These data suggest that in skeletal muscle the disruption of Tdn/CASQ link has a more profound effect on jSR architecture and myoplasmic Ca2+ regulation than Jct/CASQ association

Covalent adaptable networks using boronate linkages by incorporating TetraAzaADamantanes

Boronic esters prepared by condensation of boronic acids and diols have been widely used as dynamic covalent bonds in the synthesis of both discrete assemblies and polymer networks. In this study we investigate the potential of a new dynamic-covalent motif, derived from TetraAzaADamantanes (TAADs), with their adamantane-like triol structure, in boronic ester-based covalent adaptable networks (CANs). The TetraAzaADamantane-boronic ester linkage has recently been reported as a more hydrolytically stable boronic ester variant, while still having a dynamic pH response: small-molecule studies found little exchange at neutral pH, while fast exchange occurred at pH 3.8. In this work, bi- and trifunctional TetraAzaADamantane linkers were synthesised and crosslinked with boronic acids to form rubber-like materials, with a Young’s modulus of 1.75 MPa. The dynamic nature of the TetraAzaADamantane networks was confirmed by stress relaxation experiments, revealing Arrhenius-like behaviour, with a corresponding activation energy of 142 ± 10 kJ/mol. Increasing the crosslinking density of the material from 10% to 33% resulted in reduced relaxation times, as is consistent with a higher degree of crosslinking within the dynamic networks. In contrast to the reported accelerating effect of acid addition to small-molecule TetraAzaADamantane complexes, within the polymer network the addition of acid increased relaxation times, suggesting unanticipated interactions between the acid and the polymer that cannot occur in the corresponding small-molecules analogues. The obtained boronate-TetraAzaADamantane materials were thermally stable up to 150°C. This thermal stability, in combination with the intrinsically dynamic bonds inside the polymer network, allowed these materials to be reprocessed and healed after damage by hot-pressing

GraphIAST: A graphical user interface software for Ideal Adsorption Solution Theory (IAST) calculations

Industrial exhaust gases have a strong environmental impact, including on global warming. Carbon dioxide (CO2) is a prominent example of such an exhaust gas. Therefore, CO2 capture and storage in industrial processes is becoming increasingly important. Preferably, these emitted gases are separated before their release into the environment. Such applications require selective gas separation to isolate the harmful gases or to allow recycling of industrially relevant gases. Porous materials are promising candidates to achieve gas separation, since their large surface area enables them to adsorb large quantities while their selectivity can be tuned by controlling their chemical composition. Modelling adsorption behavior and calculating corresponding selectivities in multicomponent gas mixtures of such porous materials, which is essential to quantify their gas separation performance, can be achieved through the Ideal Adsorption Solution Theory (IAST), which can be challenging to perform. The current available softwares for IAST calculations demand programming knowledge that not every materials scientist has or has access to, limiting the development of new porous materials for gas separation purposes. In this paper, we present a simple, user-friendly program for IAST loading and selectivity predictions for binary gas mixtures based on the Python module pyIAST. We have developed a graphical user interface resembling commonly known software and made three-dimensional selectivity predictions easily accessible within just a few clicks. The input and output data structure relies on the widely used *.csv format and isotherm data can be fitted with various established models. Therefore, our software provides a platform for IAST calculations for non-programming researchers, which is expected to enable more materials scientists to screen their porous materials for desired gas separation properties. Program summary: Program Title: GraphIAST CPC Library link to program files: https://doi.org/10.17632/ytc64xwcr5.1 Developer's repository link: https://github.com/ORC-WUR/GraphIAST Licensing provisions: MIT Programming language: Python External Routines: Math, Matplotlib, Numpy, Pandas, PIL, pyIAST, Tkinter Supplementary material: User Manual, Case studies Nature of problem: Using IAST to predict the selectivity in binary gas mixtures based on their pure component isotherms. Solution method: Employing the pyIAST package [1] and incorporating this into a GUI surrounding for a facilitated use of IAST analysis. Additionally, the selectivity predictions have been extended to multiple selectivities at different mole fractions and pressures. References: [1] C.M. Simon, B. Smit, M. Haranczyk, Comput. Phys. Commun. 200 (2016) 364–380

Cell surface exposure of phosphatidylserine in propidium iodide negative thymocytes undergoing cell death by necrosis

Phosphatidylserine (PS) exposure on propidium iodide negative cells using FITC labelled annexin-V has been used to quantify apoptosis in vitro and in vivo. Detection of PS with in cells undergoing necrosis is also possible if labelled annexin-V specific for PS enters the cell following early membrane damage. Necrotic or late apoptotic cells can be excluded from flow cytometric analysis using propidium iodide which enters and stains cells with compromised membrane integrity. Here we show that thymocytes undergoing death exclusively by necrosis show early exposure of PS prior to loss of membrane integrity. This early exposure of PS occurs in cells treated with agents which both raise intracellular calcium levels and are also capable of interacting with protein thiol groups. We also demonstrate that PS exposure in thymocytes induced to undergo apoptosis by three different agents does not correlate with calcium rises but correlates with and precedes DNA fragmentation

Influx of calcium through a redox sensitive plasma membrane channel in thymocytes causes early necrotic cell death induced by the epipolythiodioxopiperazine toxins

Gliotoxin, a member of the epipolythiodioxopiperazine (ETP) class of toxins, induces both apoptotic and necrotic cell death in a concentration-dependent manner. Whereas the specific trigger for apoptotic death caused by these toxins is unclear, the reactive disulfide bond in the ETP toxins is required for biological activity. Thus it is likely that it is the interaction of this disulfide moiety with macromolecules in cells that was responsible for activity of ETP toxins. Here we present evidence that necrosis induced by gliotoxin and a simple synthetic ETP toxin is largely because of an influx of extracellular calcium through a redox-sensitive calcium channel in the plasma membrane of murine thymocytes. The calcium rises are strongly dependent on the pH of the external medium and the presence of external calcium and are abrogated and/or reversed by the presence of dithiothreitol, cell impermeant glutathione, and the calcium channel blocker Ni2. Comparisons with thapsigargin, which indirectly causes release of calcium from internal stores, indicates that ETP toxins do not provoke calcium rises by store depletion. A mechanism of oxidation by ETP toxins of cell surface thiol groups resulting in direct entry of calcium through a redox active channel in the plasma membrane is proposed. Necrotic but not apoptotic cell death was abrogated by inhibition of calcium entry

Oxidant-responsive ferrocene-based cyclodextrin complex coacervate core micelles

Coacervate-core micelles are considered promising materials for several applications, from catalysis to drug delivery. However, oxidant-responsive coacervate-core micelles, able to undergo structural changes upon specific oxidation stimuli, are not well reported. Here, we present a novel ferrocene–dipicolinic acid derivative as redox-responsive subcomponent to be incorporated in cyclodextrin-based coacervate core micelles, C4Ms, with tuneable core structure and responsiveness towards H2O2 treatment. The Fc-C4Ms are formed combining three orthogonal supramolecular interactions, namely (i) metal-to-ligand coordination between europium(III) ions and dipicolinic acid molecules, (ii) host-guest interaction between beta cyclodextrins and ferrocenes and (iii) electrostatic coacervation interaction. The micelle stability against oxidation can be controlled by varying three main parameters: (a) the core-unit structure, from monomeric metal complexes to supramolecular oligomers, (b) the H2O2 equivalents and c) the ratio between redox-responsive and non-redox-responsive bislinker. The H2O2-responsive ferrocene-based systems might have an interesting application, e.g. reactive oxygen species-mediated drug delivery.</p