Slow Spin Relaxation in Two-Dimensional Electron Systems with Antidots

We report a Monte Carlo investigation of the effect of a lattice of antidots on spin relaxation in twodimensional electron systems. The spin relaxation time is calculated as a function of geometrical parameters describing the antidot lattice, namely, the antidot radius and the distance between their centers. It is shown that spin polarization relaxation can be efficiently suppressed by the chaotic spatial motion due to the antidot lattice. This phenomenon offers a new approach to spin coherence manipulation in spintronics devices.Comment: submitted to Phys. Rev.

Synthesis of New Functionally Substituted 9-Azabicyclo[4.2.1]nona-2,4,7-trienes by Cobalt(I)-Catalyzed [6π + 2π]-Cycloaddition of N-Carbocholesteroxyazepine to Alkynes

Catalytic [6π + 2π]-cycloaddition of N-carbocholesteroxyazepine with functionally substituted terminal alkynes and 1,4-butynediol was performed for the first time under the action of the Co(acac)2(dppe)/Zn/ZnI2 three-component catalytic system. The reaction gave previously undescribed but promising 9-azabicyclo[4.2.1]nona-2,4,7-trienes (in 79–95% yields), covalently bound to a natural metabolite, cholesterol. The structure of the synthesized azabicycles was confirmed by analysis of one- and two-dimensional (1H, 13C, DEPT 13C, COSY, NOESY, HSQC, HMBC) NMR spectra

Pentacyclic Triterpenoids-Based Ionic Compounds: Synthesis, Study of Structure–Antitumor Activity Relationship, Effects on Mitochondria and Activation of Signaling Pathways of Proliferation, Genome Reparation and Early Apoptosis

The present research paper details the synthesis of novel ionic compounds based on triterpene acids (betulinic, oleanolic and ursolic), with these acids acting both as anions and connected through a spacer with various nitrogen-containing compounds (pyridine, piperidine, morpholine, pyrrolidine, triethylamine and dimethylethanolamine) and acting as a cation. Based on the latter, a large number of ionic compounds with various counterions (BF4-, SbF6-, PF6-, CH3COO-, C6H5SO3-, m-C6H4(OH)COO- and CH3CH(OH)COO-) have been synthesized. We studied the cytotoxicity of the synthesized compounds on the example of various tumor (Jurkat, K562, U937, HL60, A2780) and conditionally normal (HEK293) cell lines. IC50 was determined, and the influence of the structure and nature of the anion and cation on the antitumor activity was specified. Intracellular signaling, apoptosis induction and effects of the most active ionic compounds on the cell cycle and mitochondria have been discussed by applying modern methods of multiparametric enzyme immunoassay and flow cytometry

Natural Acetogenins, Chatenaytrienins-1, -2, -3 and -4, Mitochondrial Potential Uncouplers and Autophagy Inducers—Promising Anticancer Agents

The present paper details the complete stereoselective synthesis of four natural acetogenins, chatenaytrienins-1, -2, -3 and -4, previously isolated from the roots of fruit trees of the family Annonaceae (A. nutans and A. muricata), as an inseparable mixture. The novel organometallic reactions, developed by the authors, of Ti-catalyzed cross-cyclomagnesiation of O-containing and aliphatic allenes using available Grignard reagents were applied at the key stage of synthesis. We have studied the biological activity of the synthesized individual chatenaytrienins-1, -2, -3 and -4 in vitro, including their cytotoxicity in a panel of tumor lines and their ability to induce apoptosis, affect the cell cycle and mitochondria, and activate the main apoptotic signaling pathways in the cell, applying modern approaches of flow cytometry and multiplex analysis with Luminex xMAP technology. It has been shown that chatenaytrienins affect mitochondria by uncoupling the processes of mitochondrial respiration, causing the accumulation of ROS ions, followed by the initiation of apoptosis. The most likely mechanism for the death of cortical neurons from the consumption of tea from the seeds of Annona fruit is long-term chronic hypoxia, which leads to the development of an atypical form of Parkinson’s disease that is characteristic of the indigenous inhabitants of Guam and New Caledonia

Synthesis and Anticancer Activity of Hybrid Molecules Based on Lithocholic and (5<i>Z</i>,9<i>Z</i>)-Tetradeca-5,9-dienedioic Acids Linked via Mono(di,tri,tetra)ethylene Glycol and α,ω-Diaminoalkane Units

For the first time, hybrid molecules were synthesized on the basis of lithocholic and (5Z,9Z)-1,14-tetradeca-5,9-dienedicarboxylic acids, obtained in two stages using the homo-cyclomagnesiation reaction of 2-(hepta-5,6-diene-1-yloxy)tetrahydro-2H-pyran at the key stage. The resulting hybrid molecules containing 5Z,9Z-dienoic acids are of interest as novel synthetic biologically active precursors to create modern drugs for the treatment of human oncological diseases. The synthesized hybrid molecules were found to exhibit extremely high in vitro inhibitory activity against human topoisomerase I, which is 2–4 times higher than that of camptothecin, a known topoisomerase I inhibitor. Using flow cytometry and fluorescence microscopy, it was first shown that these new molecules are efficient apoptosis inducers in HeLa, U937, Jurkat, K562, and Hek293 cell cultures. In addition, the results of investigations into the effect of the synthesized acids on mitochondria and studies of possible DNA damage in Jurkat tumor cells are also presented

Fullerenyl-1,2,3-Triazoles: Synthesis and Cytotoxic Activity

Through the reaction of fullerenylazide with terminal acetylenes, previously undescribed 1-butyl-2-triazolylfullerenes, in which the heterocyclic fragment was directly attached to the fullerene backbone, were synthesized for the first time. Water-soluble complexes of the synthesized adducts of fullerene with polyvinylpyrrolidone showed a high cytotoxic activity towards tumor cells of the Jurkat, K562, and U937 lines

Aluminacyclopentanes in the synthesis of 3-substituted phospholanes and α,ω-bisphospholanes

An efficient one-pot process for the synthesis of 3-substituted phospholanes and α,ω-bisphospholanes was developed. The method involves the replacement of aluminium in aluminacyclopentanes, prepared in situ by catalytic cycloalumination of α-olefins and α,ω-diolefins, by phosphorus atoms on treatment with dichlorophosphines (R′PCl2). Hydrogen peroxide oxidation and treatment with S8 of the synthesized phospholanes and α,ω-bisphospholanes afforded the corresponding 3-alkyl(aryl)-1-alkyl(phenyl)phospholane 1-oxides, 3-alkyl(aryl)-1-alkyl(phenyl)phospholane 1-sulfides, bisphospholane 1,1'-dioxides, and bisphospholane 1,1'-disulfides in nearly quantitative yields. The complexes LMo(CO)5 (L = 3-hexyl-1-phenylphospholane, 3-benzyl-1-methylphospholane, 1,2-bis(1-phenylphospholan-3-yl)ethane, and 1,6-bis(1-phenylphospholan-3-yl)hexane were prepared by the reaction of 3-substituted phospholanes and α,ω-bisphospholanes with molybdenum hexacarbonyl. The structure of the complexes was proved by multinuclear 1H, 13C, and 31P spectroscopy