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991.
Pavel G. Khalatur Alexei R. Khokhlov Irina A. Nyrkova Alexander N. Semenov 《Macromolecular theory and simulations》1996,5(4):713-747
We present the results of extensive molecular dynamics and Monte Carlo studies of the self-organization in the solution of short polymer chains with strongly attracting head groups at their end. The formation of micelles (multiplets) is studied in detail. Both two dimensional (2d) and three-dimensional (3d) systems are considered. The off-lattice and lattice models under study incorporate physical factors which control micelle structure and growth in the so-called superstrong segregation regime. These factors include (i) conformational effects associated with short-range excluded-volume interaction between the tails of flexible-chain molecules and (ii) very strong attraction of head groups. Our computer simulations of 3d micelles, constructed a priori from chains with strong attraction of head groups (with the characteristic energy ≈ 10 kBT), show that size and shape of the micellar core depends crucially on the radius rc of the interaction of head-groups. If the value of rc is comparable with chain length, then micelles of nearly spherical shape emerges. The decrease of rc can induce a sharp polymorphic transition from the micellar core which is spheric in shape to a disk-like (bilayer-shaped) aggregate. Such molecular organization differs from the commonly held notion of a radially symmetric micellar core. On the other hand, these findings fall into line with a recent theory of the super strong segregation regime. When the starting configuration is a random one (i.e., no micelles were a priori formed) the type of final microstructures, emerging as a result of micellization in the superstrong segregation regime, also depends essentially on the radius of head-head attraction. In the case of three-dimensional systems and/or short range attractive potentials we always obtain many small spherically shaped aggregates which, once formed at initial stages of micellization, remain stable for all time scales. Such a behavior is due to both the strong head-head attraction and the screening (repulsive) action of micellar shells creating insurmountable potential barriers. As a result, we deal with kinetically “frozen-in” microstructures which are not reversible and cannot exchange molecules with one another. In dense systems, we observe the formation of a (quasi) periodic pattern of alternating microdomains. 相似文献
992.
Fuks Olga Ibrahima Fayadhoi Tomin Pavel A. Tchelepi Hamdi 《Transport in Porous Media》2020,132(1):113-133
Transport in Porous Media - The paper presents a novel approach for uncertainty propagation in multicomponent two-phase displacements. This approach originates from and extends the frozen... 相似文献
993.
Dmitriy V. Maltsev Alexander A. Spasov Pavel M. Vassiliev Maria O. Skripka Mikhail V. Miroshnikov Andrey N. Kochetkov Nataliya V. Eliseeva Yuliya V. Lifanova Tatyana A. Kuzmenko Lyudmila N. Divaeva Anatolii S. Morkovnik 《Molecules (Basel, Switzerland)》2021,26(19)
A number of novel 2,3,4,5-tetrahydro[1,3]diazepino[1,2-a]benzimidazole derivatives 2 were obtained by alkylation mainly in the 1H-tautomeric form of 2,3,4,5-tetrahydro[1,3]diazepino[1,2-a]benzimidazole or its 8,9-dimethyl-substituted analog 4-chlorobenzyl bromide, 4-chloroacetic acid fluoroanilide, and 4-tert-butylphenacyl bromide in neutral medium. Compounds 3 were cyclized and synthesized earlier with 11-phenacyl-substituted diazepino[1,2-a]benzimidazoles upon heating in conc. HBr. The chemical structures of the compounds were clarified by using the 1H Nuclear Magnetic Resonance Spectroscopy (1H-NMR) technique. Anxiolytic properties were evaluated using the elevated plus maze (EPM) and open field (OF) tests. The analgesic effect of compounds was estimated with the tail flick (TF) and hot plate (HP) methods. Besides, possible the influence of the test compounds on motor activities of the animals was examined by the Grid, Wire, and Rotarod tests. Compounds 2d and 3b were the most active due to their prominent analgesic and anxiolytic potentials, respectively. The results of the performed in silico analysis showed that the high anxiolytic activity of compound 3b is explained by the combination of a pronounced interaction mainly with the benzodiazepine site of the GABAA receptor with a prominent interaction with both the specific and allosteric sites of the 5-HT2A receptor. 相似文献
994.
Alexander S. Lyakhov Sergey V. Voitekhovich Pavel N. Gaponik Ludmila S. Ivashkevich 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(7):o388-o389
The title compound, C8H13N5, is a novel functionally substituted 5‐alkyltetrazole. The substituent on the tetrazole C atom is symmetrical, with intrinsic symmetry close to m. There is intermolecular N—H⃛N hydrogen bonding between adjacent tetrazole rings, which is responsible for the formation of one‐dimensional polymeric chains running along the c axis. The polycrystalline compound exhibits frequency doubling for incident light (λ = 1064 nm) from a YAG:Nd pulsed laser. 相似文献
995.
Jaromír Marek Pavel Kopel Zdenk Trvní
ek 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(12):m558-m560
In the crystal structure of the title compound, [N,N′‐bis(3‐aminopropyl)ethylenediamine‐κ4N,N′,N′′,N′′′][1,3,5‐triazine‐2,4,6(1H,3H,5H)‐trithionato(2−)‐κ2N,S]zinc(II) ethanol solvate, [Zn(C8H22N4)2(C3HN3S3)]·C2H6O, the ZnII atom is octahedrally coordinated by four N atoms [Zn—N = 2.104 (2)–2.203 (2) Å] of a tetradentate N‐donor N,N′‐bis(3‐aminopropyl)ethylenediamine (bapen) ligand and by two S and N atoms [Zn—S = 2.5700 (7) Å and Zn—N = 2.313 (2) Å] of a trithiocyanurate(2−) (ttcH2−) dianion bonded as a bidentate ligand in a cis configuration. The crystal structure of the compound is stabilized by a network of hydrogen bonds. 相似文献
996.
Alexander S. Lyakhov Andrey N. Vorobiov Pavel N. Gaponik Ludmila S. Ivashkevich Vadim E. Matulis Oleg A. Ivashkevich 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(12):o690-o693
In the molecules of 5‐amino‐1‐phenyltetrazole, C7H7N5, (I), and 5‐amino‐1‐(1‐naphthyl)tetrazole, C11H9N5, (II), the tetrazole rings and aryl fragments are not coplanar; corresponding dihedral angles are 50.58 (5) and 45.19 (7)° for the two independent molecules of (I), and 64.14 (5)° for (II). Intermolecular N—H⋯N hydrogen bonds between the amino groups and tetrazole N atoms are primarily responsible for formation of two‐dimensional networks extending parallel to the bc plane in both compounds. The presence of the amino group has a distinct effect on the geometry of the tetrazole rings in each case. 相似文献
997.
Pavel Pospisil BeatriceD. Pilger Stefania Marveggio Pierre Schelling Christine Wurth Leonardo Scapozza Gerd Folkers Mario Pongracic Mladen Mintas SilvanaRaic Malic 《Helvetica chimica acta》2002,85(10):3237-3250
In the context of broadening the knowledge on substrate specificity of Herpes simplex virus type 1 thymidine kinase (HSV‐1 TK) and Varicella‐Zoster virus thymidine kinase (VZV TK), new derivatives of 9‐(2‐hydroxypropyl)‐substituted adenine, chloropurine, hypoxanthine, guanine, thiopurine, and (methylsulfanyl)purine were synthesized and subjected to in vitro phosphorylation and binding affinity assays. The interactions between the compounds and the crystallographically determined active site residues of HSV‐1 TK have been studied by molecular modeling with the Lamarckian genetic algorithm of docking program AutoDock 3.0. All compounds mentioned bind to both enzymes in the low mM to sub‐mM range, comparable to binding affinities of existing prodrugs. Findings from the docking procedure indicate multiple binding modes for all of the compounds and are in accordance with the results of phosphorylation and binding‐affinity studies. Furthermore, the studies reveal that hypoxanthine derivatives represent a new class of TK substrates and thiopurine derivatives a new class of TK inhibitors. 相似文献
998.
999.
Irene L. Odinets Natalya M. Vinogradova Konstantin A. Lyssenko Michail Yu. Antipin Pavel V. Petrovskii Tatyana A. Mastryukova 《Heteroatom Chemistry》2002,13(1):1-21
Intramolecular S‐alkylation in a series of ω‐haloalkyl‐substituted thiophosphorylacetonitriles 5–7 presents an effective synthetic route to the hitherto unknown 3‐cyano‐2‐oxo‐1,2‐thiaphospholanes 14 and thiaphosphinanes 15 . The compounds were obtained as a mixture of cis‐ and trans‐isomers that were resolved to individual stereoisomers in most cases. For some of them, X‐ray diffraction analysis has been performed. It was shown that 31P NMR spectroscopy can be used to assign the stereochemistry of 3‐cyano‐2‐oxo‐1,2‐thiaphosphacyclanes. © 2002 John Wiley & Sons, Inc. Heteroatom Chem 13:1–21, 2002; DOI 10.1002/hc.1101 相似文献
1000.
Alexandr I. Alimpiev Valeri S. Gulev Pavel W. Mokruchniko 《Crystal Research and Technology》1995,30(3):295-297
The fields of crystallization in the system La2O3–BeO–Al2O3 are investigated. Single crystals of LaBeAl11O19 were grown by the Czochralski technique. 相似文献