Monte Carlo modeling of chiral adsorption on nanostructured chiral surfaces and slit pores

Adsorptive separation of chiral molecules is a powerful technique that has long been used in the chemical and pharmaceutical industries. An important challenge in this field is to design and optimize new adsorbents to provide selective discrimination of enantiomers. In this article, we introduce an off-lattice model of chiral adsorption on nanostructured surfaces and slit pores with the aim of predicting their enantioslective properties. The concept presented here involves finding the optimal chiral pattern of active sites on the pore walls that maximizes the difference between the binding energies of the enantiomers. Our initial effort focuses on chiral molecules that do not have specific interactions with the pore surface. One candidate meeting this requirement is 1,2-dimethylcyclopropane (DMCP), a chiral hydrocarbon whose interaction with a model pore surface was described using the Lennard-Jones potential. To model the adsorption of DMCP, we used the Monte Carlo simulation method. It was demonstrated that the separation of the enantiomers of DMCP is hardly obtainable because of the smoothness of the potential energy surface for molecules physisorbed in the pore. However, the simulated results allowed the identification of key factors that influence the binding of the enantiomers of DMCP to the pore walls with a special distribution of active sites. This information will be useful in future considerations of the adsorption of more complex chiral molecules.     

Ab Initio Study of H-Bond Dynamics in Three-Component Crystals Comprising (DABCOH+)n Polycationic Chains

In this work, the dynamic character of hydrogen-bond (H-bond) networks in two three-component crystals comprising polycationic chains was described. The first studied system was 1,4-diazabicyclo[2.2.2]octan-1-ium (DABCOH⁺) sulfamate monohydrate, known for its large negative linear compressibility. The second analyzed material was the newly obtained polar salt co-crystal: 1,4-diazabicyclo[2.2.2]octan-1-ium sulfamate urea. X-ray diffraction measurements enabled us to study the H-bond systems in both crystals using the graph set analysis. Obtained structures served as the initial models for Born-Oppenheimer molecular dynamics computations. A detailed study of intermolecular interactions and power spectra was conducted. The analysis of time and space correlations between the changes in H-bonds enabled the detection of proton transfer occurring in both systems at 300 K. Further study of those dynamic phenomena was done using the Energy Decomposition Analysis for selected trajectory fragments. Our work should improve the understanding of dielectric and ferroelectric properties of hybrid organic-inorganic materials.     

Cellular Mechanistic Considerations on Cytotoxic Mode of Action of Phosphino Ru(II) and Ir(III) Complexes

Two piano-stool ruthenium(II) complexes Ru(η⁶-p-cymene)Cl₂PPh₂CH₂OH ( RuPOH ) and Ru(η⁶-p-cymene)Cl₂P(p-OCH₃Ph)₂CH₂OH ( RuMPOH ) and two half-sandwich iridium(III) complexes Ir(η ⁵-Cp*)Cl₂PPh₂CH₂OH ( IrPOH ) and Ir(η ⁵-Cp*)Cl₂P(p-OCH₃Ph)₂CH₂OH ( IrMPOH ) have been studied in terms of potential anticancer activity on previously selected cell line (human lung adenocarcinoma). Based on experimental results obtained in monoculture in vitro model mechanistic considerations on the possible cellular modes of action have been carried out. ICP-MS analysis revealed the higher cellular uptake for less hydrophobic Ir(III) complexes in comparison to the corresponding Ru(II) compounds. Cytometric analysis showed a predominance of apoptosis over the other types of cell death for all complexes. The apoptotic pathway was confirmed by a decrease in mitochondrial membrane potential and the activation of caspases-3/9 for both Ru(II) and Ir(III) complexes. It was concluded that in the case of Ru(II) complexes the intense ROS generation is mainly responsible for the resulting cytotoxicity. The corresponding Ir(III) complexes trigger simultaneously at least three different cytotoxic pathways i. e., depletion of mitochondrial potential, activation of caspases-dependent apoptosis, and ROS-associated oxidation. Thus, it can be assumed that the final accumulation of toxic effects over time via parallel activation of different pathways results in the highest cytotoxicity in vitro exhibited by Ir(III) complexes when compared with Ru(II) complexes.     

Synthesis,characterization and photoluminescence of 8-oxyquinolinato organoboron complexes derived from pyrazole

A one-pot protocol was developed for the synthesis of a series of luminescent heteroleptic diaryldiborinic complexes containing the central aryl ring bonded to two boron atoms substituted with pyrazole and complexed with 8-hydroxyquinoline. The luminescent properties of these compounds were measured. In dilute solutions they exhibited an emission at ca. 513 nm with quantum yields of 22–27% which are typical for borinic 8-hydroxyquinoline complexes. The only exception was the complex containing the bithiophene scaffold, for which no fluorescence was observed. The obtained pyrazole-based complexes show improved solubility and thermal stability with respect to their phenyl analogues. The experimental UV–vis absorption and emission data are supported by theoretical calculations of the frontier molecular orbitals, revealing the aromatic linker to quinolinato ligand excitation mechanism.     

Diauxic Growth at the Mesoscopic Scale

In the present paper, we study a diauxic growth that can be generated by a class of model at the mesoscopic scale. Although the diauxic growth can be related to the macroscopic scale, similarly to the logistic scale, one may ask whether models on mesoscopic or microscopic scales may lead to such a behavior. The present paper is the first step towards the developing of the mesoscopic models that lead to a diauxic growth at the macroscopic scale. We propose various nonlinear mesoscopic models conservative or not that lead directly to some diauxic growths.     

Light-Driven Diselenide Metathesis in Peptides

Peptides containing selenocysteine moieties are susceptible to non-catalytic reactions of diselenide bonds metathesis induced by visible light. In contrast to previously reported radical metathesis of disulfide bridges in cysteine derivatives, this newly developed reaction is fast and clean, and proceeds without decomposition of peptides and without formation of side products. The diselenide bond in peptides was reported in literature to be more stable than the disulfide one and also less susceptible to metathesis induced by thiols and reducing reagents. We demonstrated that visible light induces fast metathesis of Se−Se bonds in peptides. This reaction is important for the folding of peptides containing selenocysteine residues and may find application in designing dynamic combinatorial libraries of peptides responsive to external influence.     

Effective Microorganisms (EM) Improve Internal Organ Morphology,Intestinal Morphometry and Serum Biochemical Activity in Japanese Quails under Clostridium perfringens Challenge

The effect of effective microorganisms (EM) on internal organ morphology, intestinal morphometry, and serum biochemical activity in Japanese quails under Clostridium perfringens challenge was determined. After 30 days of EM addition, one group of quails was orally inoculated with Clostridium perfringens. The second group did not receive EM and was inoculated with C. perfringens. In the gut, EM supplementation reduced the number of lesions, enhanced gut health, and protected the mucosa from pathogenic bacteria. EM showed an anti-inflammatory effect and fewer necrotic lesions in villi. In the internal organs, EM showed a protective effect against a typical lesion of C. perfringens infection. Necrosis and degeneration of the hepatocytes, necrosis of bile ducts, and bile duct proliferation were more severe in the infected group without EM. Morphometric evaluation showed significantly higher villi in the jejunum after EM addition. A greater crypt depth was observed in the C. perfringens group. Biochemical analysis of the blood indicated lower cholesterol on the 12th day of the experiment and between-group differences in total protein, lactate dehydrogenase (LDH), and albumin levels in the EM group. Further studies are needed to improve EM activity against pathologic bacteria as a potential alternative to antibiotics and to develop future natural production systems.     

Temperature as an Extra Dimension in Multidimensional Protein NMR Spectroscopy

NMR spectroscopy is a particularly informative method for studying protein structures and dynamics in solution; however, it is also one of the most time-consuming. Modern approaches to biomolecular NMR spectroscopy are based on lengthy multidimensional experiments, the duration of which grows exponentially with the number of dimensions. The experimental time may even be several days in the case of 3D and 4D spectra. Moreover, the experiment often has to be repeated under several different conditions, for example, to measure the temperature-dependent effects in a spectrum (temperature coefficients (TCs)). Herein, a new approach that involves joint sampling of indirect evolution times and temperature is proposed. This allows TCs to be measured through 3D spectra in even less time than that needed to acquire a single spectrum by using the conventional approach. Two signal processing methods that are complementary, in terms of sensitivity and resolution, 1) dividing data into overlapping subsets followed by compressed sensing reconstruction, and 2) treating the complete data set with a variant of the Radon transform, are proposed. The temperature-swept 3D HNCO spectra of two intrinsically disordered proteins, osteopontin and CD44 cytoplasmic tail, show that this new approach makes it possible to determine TCs and their non-linearities effectively. Non-linearities, which indicate the presence of a compact state, are particularly interesting. The complete package of data acquisition and processing software for this new approach are provided.