On the numerical solution of axisymmetric domain optimization problems by dual finite element method

Shape optimization of an axisymmetric three-dimensional domain with an elliptic boundary value state problem is solved. Since the cost functional is given in terms of the cogradient of the solution, a dual finite element method based on the minimum of complementary energy principle is used. © 1994 John Wiley & Sons, Inc.     

Quantitative approach to hückel rule the relations between the cycles of a molecular graph and the thermodynamic stability of a conjugated molecule

Contribution of the rings to the total π-electron energy (CE) is calculated for a number of polycyclic conjugated hydrocarbons. The Hückel 4m+2 rule is tested quantitatively in this way. It is shown that (4m)-membered rings always destabilize, while (4m + 2)-membered rings almost always stabilize the molecule. The magnitude of this effect is, however, subject to considerable variations. The main factors which determine the magnitude of CE are discussed. Examples of the alternant hydrocarbons are found for which the (4m + 2)-membered cycles have a destabilizing effect, and therefore violate the Hückel rule. The odd membered cycles are shown to have a negligibly small effect on the stability of the conjugated molecules.     

Near infrared electronic spectrum of TCNQ mono-valent anion

The high resolution near infrared electronic spectrum of TCNQ anion dissolved in 2-methyltetrahydrofuran glass at 77 K has been determined. The absorption bands are interpreted as simple progressions of two molecular vibrations in a single electronic excited state with ν₀₀ = 11661 cm^?1. The molecular vibrations (ω′₁ = 1264 ± 3 cm^?1, ω′₂ = 335 ± 3 cm^?1) of the vibrational progression agree well with observed Raman active transitions. The experimental data do not require the presence of two electronic transitions in the 1.3 to 2.1 eV region, contrary to what had been assumed previously on the basis of less well resolved room temperature spectra.     

Strained aromatic oligoamide macrocycles as new molecular clips

Can one join both ends of a helix? A helical aromatic oligoamide was macrocyclized into a saddle-shaped bifunctional clip molecule that self-assembles into discrete circular dodecamers in the solid state and shows great potential for binding aromatic acid guests in solution. The cyclization step requires that the helix is only partly denatured in the reaction medium.     

A parallel implementation of the COLUMBUS multireference configuration interaction program

Summary In this work a parallel implementation of the COLUMBUS MRSDCI program system is presented. A coarse grain parallelization approach using message passing via the portable toolkit TCGMSG is used. The program is very well portable and runs on shared memory machines like the Cray Y-MP, Alliant FX/2800 or Convex C2 and on distributed memory machines like the iPSC/860. Further implementations on a network of workstations and on the Intel Touchstone Delta are in progress. Overall, results are quite satisfactory considering the complexity and the prodigious requirements, especially the I/O bandwidth, of MRCI programs in general. For our largest test case we obtain a speedup of a factor of 7.2 on an eight processor Cray Y-MP for that section of the program (hamiltonian matrix times trial vector product) which has been parallelized. The speedup for one complete diagonalization iteration amounts to 5.9. An absolute speed close to 1 GFLOPS is found. Results for the iPSC/860 show that ordinary disk I/O is certainly not sufficient in order to guarantee a satisfactory performance. As a solution for that problem, the implementation of a fully asynchronous distributed-memory model for certain data files is in preparation. On leave from: Bereich Informatik, Universität Leipzig, Augustusplatz 10/11, O-7010 Leipzig, Germany     

5-(N-Arylnortropan-3-yl)- and 5-(N-Arylpiperidin-4-yl)-2,4-diaminopyrimidines. Novel Inhibitors of Dihydrofolate Reductase

Based on a computer-assisted analysis of the three-dimensional structure of the binary complex of E.coli dihydrofolate reductase (DHFR) with methotrexate, 5-(N-arylnortropan-3-yl)- and 5-(N-arylpiperidin-4-yl)-2,4-diaminopyrimidines 2 and 4 were designed as inhibitors of DHFR. Syntheses of the designed compounds have been carried out. The most potent compound 2a inhibited E. coli DHFR with K_i = 0.49.10^?9M. The activities within the series of compounds synthesized could be rationalized by molecular-modelling experiments which served as the basis of this work. Several compounds within the presented series exhibit antimalarial activities in vitro and in vivo.     

The separation of some Bi- and tervalent cations on zirconium phosphate columns

Summary On small columns filled with the inorganic cation-exchanger zirconium phosphate, Zn²⁺-Cd²⁺ were quantitatively and Ni²⁺-Co²⁺ partly separated. The exchanger was in the NH₄+ form, and 0.5–4N NH₄Cl served as eluent. With the exchanger in the H+ form, U0₂ ²⁺ was separated from bivalent cations and ferric iron by stepwise elution with 0.1, 0.5 and 4N HCl solutions.

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Zusammenfassung An kleinen Säulen des anorganischen Kationenaustauschers Zirkoniumphosphat wurden Zn²⁺ und Cd²⁺ quantitativ, Ni²⁺ und Co²⁺ teilweise getrennt. Der Austauscher lag in der NH₄+-Form vor, 0,5-bis 4-n Ammoniumchlorid diente als Eluent. Mit der H+-Form des Austauschers wurde UO₂ ²⁺ von zweiwertigen Kationen und von Fe³⁺ durch schrittweise Elution mit 0,1-, 0,5- und 4-n Salzsäure getrennt.

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Résumé On a séparé Zn²⁺-Cd²⁺ quantitativement et Ni²⁺-Co²⁺ partiellement sur de petites colonnes remplies de phosphate de zirconium comme échangeur minéral cationique. L'échangeur se trouvait sous forme NH₄+ et l'on a pris NH₄Cl 0,5-4N comme éluant. Avec l'échangeur sous forme H⁺, on a séparé UO₂ ²⁺ des cations bivalents et de l'ion ferrique par élution graduelle avec des solutions chlorhydriques 0,1, 0,5 et 4N.

     

Virtual Screening and Hit Selection of Natural Compounds as Acetylcholinesterase Inhibitors

Acetylcholinesterase (AChE) is one of the classical targets in the treatment of Alzheimer’s disease (AD). Inhibition of AChE slows down the hydrolysis of acetycholine and increases choline levels, improving the cognitive function. The achieved success of plant-based natural drugs acting as AChE inhibitors, such as galantamine (GAL) from Galanthus genus and huperzine A from Huperzia serrate (approved drug in China), in the treatment of AD, and the fact that natural compounds (NCs) are considered as safer and less toxic compared to synthetic drugs, led us to screen the available NCs (almost 150,000) in the ZINC12 database for AChE inhibitory activity. The compounds were screened virtually by molecular docking, filtered for suitable ADME properties, and 32 ligands from 23 structural groups were selected. The stability of the complexes was estimated via 1 μs molecular dynamics simulation. Ten compounds formed stable complexes with the enzyme and had a vendor and a reasonable price per mg. They were tested for AChE inhibitory and antioxidant activity. Five compounds showed weak AChE inhibition and three of them exhibited high antioxidant activity.     

Synthesis and Antiviral Properties against SARS-CoV-2 of Epoxybenzooxocino[4,3-b]Pyridine Derivatives

The COVID-19 pandemic is ongoing as of mid-2022 and requires the development of new therapeutic drugs, because the existing clinically approved drugs are limited. In this work, seven derivatives of epoxybenzooxocinopyridine were synthesized and tested for the ability to inhibit the replication of the SARS-CoV-2 virus in cell cultures. Among the described compounds, six were not able to suppress the SARS-CoV-2 virus’ replication. One compound, which is a derivative of epoxybenzooxocinopyridine with an attached side group of 3,4-dihydroquinoxalin-2-one, demonstrated antiviral activity comparable to that of one pharmaceutical drug. The described compound is a prospective lead substance, because the half-maximal effective concentration is 2.23 μg/μL, which is within a pharmacologically achievable range.