Molecular Insights into Carbon Dioxide Sorption in Hydrazone-Based Covalent Organic Frameworks with Tertiary Amine Moieties

Tailorable sorption properties at the molecular level are key for efficient carbon capture and storage and a hallmark of covalent organic frameworks (COFs). Although amine functional groups are known to facilitate CO2 uptake, atomistic insights into CO2 sorption by COFs modified with amine-bearing functional groups are scarce. Herein, we present a detailed study of the interactions of carbon dioxide and water with two isostructural hydrazone-linked COFs with different polarities based on the 2,5-diethoxyterephthalohydrazide linker. Varying amounts of tertiary amines were introduced in the COF backbones by means of a copolymerization approach using 2,5-bis(2-(dimethylamino)ethoxy)terephthalohydrazide in different amounts ranging from 25 to 100% substitution of the original DETH linker. The interactions of the frameworks with CO2 and H2O were comprehensively studied by means of sorption analysis, solid-state NMR spectroscopy, and quantum-chemical calculations. We show that the addition of the tertiary amine linker increases the overall CO2 sorption capacity normalized by the surface area and of the heat of adsorption, whereas surface areas and pore size diameters decrease. The formation of ammonium bicarbonate species in the COF pores is shown to occur, revealing the contributing role of water for CO2 uptake by amine-modified porous frameworks

Molecular Tweezers with Varying Anions: A Comparative Study

Selective binding of the phosphate-substituted molecular tweezer 1a to protein lysine residues was suggested to explain the inhibition of certain enzymes and the aberrant aggregation of amyloid petide Aβ42 or α-synuclein, which are assumed to be responsible for Alzheimer’s and Parkinson’s disease, respectively. In this work we systematically investigated the binding of four water-soluble tweezers 1a−d (substituted by phosphate, methanephosphonate, sulfate, or O-methylenecarboxylate groups) to amino acids and peptides containing lysine or arginine residues by using fluorescence spectroscopy, NMR spectroscopy, and isothermal titration calorimetry (ITC). The comparison of the experimental results with theoretical data obtained by a combination of QM/MM and ab initio 1H NMR shift calculations provides clear evidence that the tweezers 1a−c bind the amino acid or peptide guest molecules by threading the lysine or arginine side chain through the tweezers’ cavity, whereas in the case of 1d the guest molecule is preferentially positioned outside the tweezer’s cavity. Attractive ionic, CH-π, and hydrophobic interactions are here the major binding forces. The combination of experiment and theory provides deep insight into the host−guest binding modes, a prerequisite to understanding the exciting influence of these tweezers on the aggregation of proteins and the activity of enzymes

Natural Genetic Variation in Selected Populations of Arabidopsis thaliana Is Associated with Ionomic Differences

Controlling elemental composition is critical for plant growth and development as well as the nutrition of humans who utilize plants for food. Uncovering the genetic architecture underlying mineral ion homeostasis in plants is a critical first step towards understanding the biochemical networks that regulate a plant's elemental composition (ionome). Natural accessions of Arabidopsis thaliana provide a rich source of genetic diversity that leads to phenotypic differences. We analyzed the concentrations of 17 different elements in 12 A. thaliana accessions and three recombinant inbred line (RIL) populations grown in several different environments using high-throughput inductively coupled plasma- mass spectroscopy (ICP-MS). Significant differences were detected between the accessions for most elements and we identified over a hundred QTLs for elemental accumulation in the RIL populations. Altering the environment the plants were grown in had a strong effect on the correlations between different elements and the QTLs controlling elemental accumulation. All ionomic data presented is publicly available at www.ionomicshub.org

RNA Oligomerisation without Added Catalyst from 2 ',3 '-Cyclic Nucleotides by Drying at Air-Water Interfaces

For the emergence of life, the abiotic synthesis of RNA from its monomers is a central step. We found that in alkaline, drying conditions in bulk and at heated air-water interfaces, 2 ',3 '-cyclic nucleotides oligomerised without additional catalyst, forming up to 10-mers within a day. The oligomerisation proceeded at a pH range of 7-12, at temperatures between 40-80 degrees C and was marginally enhanced by K+ ions. Among the canonical ribonucleotides, cGMP oligomerised most efficiently. Quantification was performed using HPLC coupled to ESI-TOF by fitting the isotope distribution to the mass spectra. Our study suggests a oligomerisation mechanism where cGMP aids the incorporation of the relatively unreactive nucleotides C, A and U. The 2 ',3 '-cyclic ribonucleotides are byproducts of prebiotic phosphorylation, nucleotide syntheses and RNA hydrolysis, indicating direct recycling pathways. The simple reaction condition offers a plausible entry point for RNA to the evolution of life on early Earth

Software for the frontiers of quantum chemistry:An overview of developments in the Q-Chem 5 package

This article summarizes technical advances contained in the fifth major release of the Q-Chem quantum chemistry program package, covering developments since 2015. A comprehensive library of exchange–correlation functionals, along with a suite of correlated many-body methods, continues to be a hallmark of the Q-Chem software. The many-body methods include novel variants of both coupled-cluster and configuration-interaction approaches along with methods based on the algebraic diagrammatic construction and variational reduced density-matrix methods. Methods highlighted in Q-Chem 5 include a suite of tools for modeling core-level spectroscopy, methods for describing metastable resonances, methods for computing vibronic spectra, the nuclear–electronic orbital method, and several different energy decomposition analysis techniques. High-performance capabilities including multithreaded parallelism and support for calculations on graphics processing units are described. Q-Chem boasts a community of well over 100 active academic developers, and the continuing evolution of the software is supported by an “open teamware” model and an increasingly modular design