Hybrid Materials Consisting of Silver(I) Purine Complexes, Protonated Purines and Polyoxometalates

The present work is the first thorough exploration of the chemistry of the systems comprising purine bases and polyoxometalates (POMs). Different modes of interplay of these chemical species were employed in order to design and synthesize new compounds. The first type consisted majorly of materials in which polyoxoanions are interconnected by ditheobromine silver(I) complexes. The convenient aspect of the synthetic procedures is the possibility of obtaining the desired POM from basic materials by adjustment of the pH value of the reaction mixture. A ubiquitous structural trait of the target materials were one-dimensional coordination polymers consisting of polyoxoanions interconnected by [Ag(thb)2]+-complexes. Compounds based on iso- and heteropolyoxometalates of vanadium, chromium and molybdenum were obtained by this reaction procedure. Several similar compounds were obtained from benzonitrile as solvent. An intriguing unusual chemoselectivity regulated by guanine was observed under these reaction conditions. The solvent partly replaced the purine bases in the coordination sphere of silver(I) due to its strong σ-donor character. The protonated purine bases could also be employed for crystal engineering of organic-inorganic materials containing polyoxotungstates. The aromatic cations are arranged parallel to the faces of the POMs in all of the resulting crystal structures. The arrangement was named “nanoboxes” reflecting the size of the units. A compound containing a purine base covalently bound to a polyoxometalate Na2[(HGMP)2(Mo5O15)]•7H2O (GMP = guanosine monophosphate), crystallizes in space group P6522, which implies a helical structure in the solid state. The crystal structure consists of guanosine Strandberg anions interconnected by a network of coordinative, H-bonding and stacking interactions

Using evolutionary algorithms and machine learning to explore sequence space for the discovery of antimicrobial peptides

We present a proof-of-concept methodology for efficiently optimizing a chemical trait by using an artificial evolutionary workflow. We demonstrate this by optimizing the efficacy of antimicrobial peptides (AMPs). In particular, we used a closed-loop approach that combines a genetic algorithm, machine learning, and in vitro evaluation to improve the antimicrobial activity of peptides against Escherichia coli. Starting with a 13-mer natural AMP, we identified 44 highly potent peptides, achieving up to a ca. 160-fold increase in antimicrobial activity within just three rounds of experiments. During these experiments, the conformation of the peptides selected was changed from a random coil to an α-helical form. This strategy not only establishes the potential of in vitro molecule evolution using an algorithmic genetic system but also accelerates the discovery of antimicrobial peptides and other functional molecules within a relatively small number of experiments, allowing the exploration of broad sequence and structural space

Geologische Untersuchungen an der Neubaustrecke Dresden-Prag: Geologische Untersuchungen an der Eisenbahn-Neubaustrecke Dresden-Prag (2011 - 2020)

In der Schriftenreihe werden alle Ergebnisse der geologischen Untersuchungen vorgestellt, die seit 2011 im Umfeld der geplanten Eisenbahnneubaustrecke Dresden-Prag durchgeführt worden sind. Der geplante mindestens 25 km lange, grenzüberschreitende Erzgebirgsbasistunnel durchquert verschiedene Gesteine und komplexe Störungszonen. Untersuchungsschwerpunkt waren die geologischen, tektonischen und hydrogeologischen Verhältnisse im grenznahen Raum des geplanten Trassenkorridos. Die Veröffentlichung richtet sich an Behörden, Institutionen, Ingenieur- und Planungsbüros, die sich mit der Umsetzung der Neubaustrecke beschäftigen sowie an die geologisch interessierte Fachwelt und Öffentlichkeit. Redaktionsschluss: 28.08.202

THE FUNCTIONAL MORPHOLOGY OF THE BRAIN HARD ENVELOPE

First in complex studied has been the solid brain envelope, including that in the system of the perimedullar tissues, using the elements of the comparative and ontogenetic approaches. The complex character of the mechanical and hydraulic interactions in the perimedullar surrounding, changing on the stages of ontogenesis, has been revealed. The obtained results have the importance for specifying the role of the perimedullar tissues in supporting the parameters of the intracranial pressure, important for the morphogenesis and homeostasis of the brain, under the normal and pathological conditions. The results of the work have been introduced on the morphological chairs of the Astrakhan, Izhevsk, Orenburg Medical Academies.Available from VNTIC / VNTIC - Scientific & Technical Information Centre of RussiaSIGLERURussian Federatio

Polyoxotungstates in Molecular Boxes of Purine Bases

Three new compounds, (GuaH)(4)[W10O32](H2O)(4) (1), (ThbH)(3)(H3O)[(W10O32](H2O)(7.5) (2) and (ThbH)(2)[W6O19](H2O)(2) (3) (GuaH = guaninium, thbH = theobrominium) were synthesized in acidified acetonitrile solutions. The polyoxotungstates in all of these compounds are surrounded by an organic matrix consisting of protonated purine bases and water molecules. The distinctive structural arrangement of the aromatic organic cations around the polyoxoanions parallel to their faces is reminiscent of nanosized boxes. The results of IR spectroscopy are consistent with previously reported results for polyoxotungstates and neat organic compounds. The polyoxoanions are reduced to tungsten(IV) oxide upon heating over 400 degrees C in an intramolecular redox reaction

Dihydronium tetrachromate(VI), (H3O)2Cr4O13

The crystal structure of (H3O)2Cr4O13 is isotypic with K2Cr4O13. The finite tetrachromate anion in the title structure consists of four vertex-sharing CrO4 tetrahedra and exhibits a typical zigzag arrangement. The crystal packing is stabilized by hydrogen bonds between these anions and hydronium cations. The two different hydronium cations are surrounded by nine O atoms of tetrachromate anions, with O...O distances ranging between 2.866 (8) and 3.282 (7) Å

Organoamine silver(I) decatungstate structures: remarkable chemoselectivity and the exploration of the intramolecular redox reaction upon thermolysis

Three new inorganic organic hybrid compounds containing silver(I) coordinated to decatungstate and organic ligands are reported. Formation of one of them is induced by guanine with high chemoselectivity. The oxidation state of tungsten in the thermal decomposition products is dependent on the organic ligands in the coordination sphere of silver(I)

A New Strategy for the Synthetic Assembly of Inorganic–Organic Silver(I)-Polyoxometalate Hybrid Structures Employing Noncovalent Interactions between Theobromine Ligands

A new strategy for the synthesis of inorganic–organic silver­(I)-polyoxometalate materials was developed. The approach takes advantage of the ability of purine bases to build strong networks using them as ligands to silver­(I). Its major experimental strong point is the facile preparation of target compounds from aqueous solutions from basic starting materials. Proof of concept was accomplished by using theobromine as the purine base. Seven new compounds containing silver­(I) theobromine building blocks were characterized by single crystal X-ray diffraction: [Ag­(thb)₂]­ClO₄ (<b>2</b>), [Ag­(thb)₂­(H₂O)]­ClO₄ (<b>3</b>), [Ag­(thb)₂]₂­(H₄V₁₀O₂₈)­·3H₂O (<b>4</b>), [Ag­(thb)₂]₂­(Cr₂O₇)­·0.5H₂O (<b>5</b>), [Ag­(thb)₂(H₂O)]₂­(H₃O)­[Ag­(β-Mo₈O₂₆)]­·4H₂O (<b>6</b>), [Ag­(thb)]₂­[Ag­(Cr­(OH)₆Mo₆O₁₈)]­·2H₂O (<b>7</b>), and [Ag­(thb)₂]₂(H₃O)₄­[Ni­(OH)₆Mo₆O₁₈]­(CO₃)­·13H₂O (<b>8</b>) (thb = theobromine). The purity of compounds <b>2</b>–<b>7</b> was confirmed by powder X-ray diffraction and elemental analysis. They were also characterized by IR and UV/vis spectroscopy and thermal analysis (DTA/TG). The main structural traits in all of the polyoxometalate containing compounds are coordination polymers running along the direction of one of the crystallographic axes. These chains are interconnected by a framework of strong hydrogen bonds and stacking interactions. The thermodynamic rationalization of these crystal structure landscapes is thoroughly discussed

A New Strategy for the Synthetic Assembly of Inorganic–Organic Silver(I)-Polyoxometalate Hybrid Structures Employing Noncovalent Interactions between Theobromine Ligands

A new strategy for the synthesis of inorganic–organic silver­(I)-polyoxometalate materials was developed. The approach takes advantage of the ability of purine bases to build strong networks using them as ligands to silver­(I). Its major experimental strong point is the facile preparation of target compounds from aqueous solutions from basic starting materials. Proof of concept was accomplished by using theobromine as the purine base. Seven new compounds containing silver­(I) theobromine building blocks were characterized by single crystal X-ray diffraction: [Ag­(thb)₂]­ClO₄ (<b>2</b>), [Ag­(thb)₂­(H₂O)]­ClO₄ (<b>3</b>), [Ag­(thb)₂]₂­(H₄V₁₀O₂₈)­·3H₂O (<b>4</b>), [Ag­(thb)₂]₂­(Cr₂O₇)­·0.5H₂O (<b>5</b>), [Ag­(thb)₂(H₂O)]₂­(H₃O)­[Ag­(β-Mo₈O₂₆)]­·4H₂O (<b>6</b>), [Ag­(thb)]₂­[Ag­(Cr­(OH)₆Mo₆O₁₈)]­·2H₂O (<b>7</b>), and [Ag­(thb)₂]₂(H₃O)₄­[Ni­(OH)₆Mo₆O₁₈]­(CO₃)­·13H₂O (<b>8</b>) (thb = theobromine). The purity of compounds <b>2</b>–<b>7</b> was confirmed by powder X-ray diffraction and elemental analysis. They were also characterized by IR and UV/vis spectroscopy and thermal analysis (DTA/TG). The main structural traits in all of the polyoxometalate containing compounds are coordination polymers running along the direction of one of the crystallographic axes. These chains are interconnected by a framework of strong hydrogen bonds and stacking interactions. The thermodynamic rationalization of these crystal structure landscapes is thoroughly discussed