Reversible Band Gap Engineering in Carbon Nanotubes by Radial Deformation

We present a systematic analysis of the effect of radial deformation on the atomic and electronic structure of zigzag and armchair single wall carbon nanotubes using the first principle plane wave method. The nanotubes were deformed by applying a radial strain, which distorts the circular cross section to an elliptical one. The atomic structure of the nanotubes under this strain are fully optimized, and the electronic structure is calculated self-consistently to determine the response of individual bands to the radial deformation. The band gap of the insulating tube is closed and eventually an insulator-metal transition sets in by the radial strain which is in the elastic range. Using this property a multiple quantum well structure with tunable and reversible electronic structure is formed on an individual nanotube and its band-lineup is determined from first-principles. The elastic energy due to the radial deformation and elastic constants are calculated and compared with classical theories.Comment: To be appear in Phys. Rev. B, Apr 15, 200

Transcriptome-based identification of PDGFA as a candidate secreted biomarker for hepatocellular carcinoma

Aim. Identification of candidate secreted biomarkers for hepatocellular carcinoma (HCC) diagnosis. Methods. Genes upregulated in HCC tissue and encoding secreted proteins were identified by RNA-seq. Gene expression changes in HCC were evaluated by RT-qPCR and meta-analysis of public databases. Biomarker properties were studied using ROC-curves, correlation and survival analysis. Results. PDGFA was identified by RNA-seq as an overexpressed gene encoding for a secreted protein in 5 HCC cases. PDGFA and GPC3 up-regulation was revealed in 17 of 19 HCC samples and in most cases from the public databases. Combination of PDGFA and GPC3 discerned HCC and non-tumor tissue better than PDGFA or GPC3 alone. PDGFA overexpression was associated with better overall survival of the patients at early HCC stage and with weaker tumor invasion into blood vessels. Conclusion. PDGFA is a valuable secreted biomarker for HCC that might be used in combination with GPC3 to increase its sensitivity.Мета. Ідентифкація потенційних біомаркерів, що секретується для діагностики гепатоцелюлярної карциноми (ГК). Методи. Гени, експресія яких підвищена в тканині ГК і які кодують білки, що секретуються, виявляли РНК-секвенуванням. Експресію генів оцінювали ЗТ-ПЛР або використовували інформацію з відкритих баз даних. Біомаркерні властивості оцінювали за допомогою ROC-кривих, аналізу кореляцій і виживання. Результати. РНК-секвенування п’яти випадків ГК виявило гіперекспресію PDGFA, що кодує секретуємий білок. Підвищення експресії PDGFA та GPC3 виявлено в 17 з 19 зразків ГК та для більшого випадку зразків у базах даних. Спільне використання PDGFA та GPC3 дозволяє точніше відрізнити ГК від непухлинної тканини печінки , ніж PDGFA або GPC3 окремо. Гіперекспресія PDGFA асоційована з кращим прогнозом для пацієнтів з ранніми стадіями ГК і низькою інвазією пухлини в судини. Висновки. PDGFA – перспективний біомаркер ГК, що секретується, який може бути використаний разом з GPC3 для підвищення його чутливості.Цель. Поиск потенциальных секретируемых биомаркеров для диагностики гепатоцеллюлярной карциномы (ГК). Методы. Гены, экспрессия которых повышена в ткани ГК и кодирующие секретируемые белки, выявляли РНК-секвенированием. Экспрессию генов оценивали ОТ-ПЦР или использовали информацию из открытых баз данных. Биомаркерные свойства оценивали с помо-щью ROC-кривых, анализа корреляций и выживаемости. Результаты. РНК-секвенирование 5 случаев ГК выявило гиперэкспрес-сию PDGFA, кодирующего секретируемый белок. Повышение экспрессии PDGFA и GPC3 выявлено в 17 из 19 образцов ГК и в большинстве случаев из баз данных. Совместное использование двух маркерных генов PDGFA и GPC3 позволяет дифференци-ровать ткань ГК от неопухолевой ткани печени лучше, чем PDGFA или GPC3 по отдельности. Гиперэкспрессия PDGFA ассо-циирована с лучшим прогнозом для пациентов с ранними стадиями ГК и низкой инвазией опухоли в сосуды. Выводы. PDGFA – перспективный секретируемый биомаркер ГК, который может быть использован вместе с GPC3 для повышения его чувстви-тельности

Eight-membered-ring diaminocarbenes bearing naphthalene moiety in the backbone: DFT studies, synthesis of amidinium salts, generation of free carbene, metal complexes, and solvent-free copper catalyzed azide-alkyne cycloaddition (CuAAC) reaction

A new type of eight-membered ring N-heterocyclic carbene (NHC) bearing a rigid naphthalene moiety in the backbone is reported for the first time. Stereoelectronic properties of 4,5-dihydro-1H-naphtho[1,8-ef][1,3]diazocin-3(2H)-ylidene (NaphtDHD) and smaller ring NHCs were theoretically studied at the DFT level. Amidinium salts were prepared from corresponding amidines and dibromides. Free carbene NaphtDHD-Dipp (Dipp = 2,6-diisopropylphenyl) was generated in solution by treatment of the corresponding salt with LiHMDS. It is stable in solution at low temperatures, while decomposing rapidly at room temperature. Silver(i) and copper(i) complexes were synthesized and structurally characterized in the solid state. The copper(i) complex [(NaphtDHD-Mes)CuBr] (Mes = mesityl, 2,4,6-trimethylphenyl) exhibits high catalytic activity in alkyne-azide cycloaddition (CuAAC) reaction under solvent-free conditions. © The Royal Society of Chemistry

Solvent-free Buchwald–Hartwig amination with low palladium loadings

A highly efficient ‘green’ solvent-free monoarylation of primary anilines with aryl bromides mediated by the expanded-ring N-heterocyclic carbene palladium complex (THP-Dipp)Pd(cinn)Cl [THP-Dipp is 1,3-bis(2,6-diisopropylphenyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene; cinn is cinnamyl] can be performed at low catalyst loadings (0.1 mol%) to provide excellent yields and remarkable selectivities for various substrates. © 201

General Method for the Synthesis of 1,4-Disubstituted 5-Halo-1,2,3-triazoles

A general method for the synthesis of 1,4-disubstituted 5-halo-1,2,3-triazoles has been developed. The one-pot two-step process consists of a CuAAC reaction of a copper(I) acetylide with an organic azide catalyzed by (aNHC)CuCl, followed by halogenation with N-chlorosuccinimide, N-bromosuccinimide, or I2. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinhei

General Method for the Synthesis of 1,4-Disubstituted 5-Halo-1,2,3-triazoles

A general method for the synthesis of 1,4-disubstituted 5-halo-1,2,3-triazoles has been developed. The one-pot two-step process consists of a CuAAC reaction of a copper(I) acetylide with an organic azide catalyzed by (aNHC)CuCl, followed by halogenation with N-chlorosuccinimide, N-bromosuccinimide, or I2. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinhei

Eight-membered-ring diaminocarbenes bearing naphthalene moiety in the backbone: DFT studies, synthesis of amidinium salts, generation of free carbene, metal complexes, and solvent-free copper catalyzed azide-alkyne cycloaddition (CuAAC) reaction

A new type of eight-membered ring N-heterocyclic carbene (NHC) bearing a rigid naphthalene moiety in the backbone is reported for the first time. Stereoelectronic properties of 4,5-dihydro-1H-naphtho[1,8-ef][1,3]diazocin-3(2H)-ylidene (NaphtDHD) and smaller ring NHCs were theoretically studied at the DFT level. Amidinium salts were prepared from corresponding amidines and dibromides. Free carbene NaphtDHD-Dipp (Dipp = 2,6-diisopropylphenyl) was generated in solution by treatment of the corresponding salt with LiHMDS. It is stable in solution at low temperatures, while decomposing rapidly at room temperature. Silver(i) and copper(i) complexes were synthesized and structurally characterized in the solid state. The copper(i) complex [(NaphtDHD-Mes)CuBr] (Mes = mesityl, 2,4,6-trimethylphenyl) exhibits high catalytic activity in alkyne-azide cycloaddition (CuAAC) reaction under solvent-free conditions. © The Royal Society of Chemistry

Solvent-free Buchwald–Hartwig amination with low palladium loadings

A highly efficient ‘green’ solvent-free monoarylation of primary anilines with aryl bromides mediated by the expanded-ring N-heterocyclic carbene palladium complex (THP-Dipp)Pd(cinn)Cl [THP-Dipp is 1,3-bis(2,6-diisopropylphenyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene; cinn is cinnamyl] can be performed at low catalyst loadings (0.1 mol%) to provide excellent yields and remarkable selectivities for various substrates. © 201

Evidence for Indirect Action of Ionizing Radiation in 18-Crown-6 Complexes with Halogenous Salts of Strontium: Simulation of Radiation-Induced Transformations in Ionic Liquid/Crown Ether Compositions

Ionic liquid/crown ether compositions are an attractive alternative to traditional extractants in the processes for spent nuclear fuel and liquid radioactive wastes reprocessing. These compositions are exposed to ionizing radiation, and their radiation stability, especially in the presence of metal salts, is a crucial issue. In the present study, the macrocyclic 18C6·Sr(BF4)2 and 18C6·Sr(PF6)2 complexes simulating the components of metal loaded ionic liquid/crown ether extractants were synthesized and their structures were characterized by FTIR spectroscopy and single-crystal X-ray diffraction analysis. Inclusion of Sr2+ cation into the 18C6 cavity resulted in more symmetric D3d conformations of the macrocycle. The structural transformations of the crown ether were accompanied by an elongation of polyether C - O bonds that could increase the possibility of radiolytic cleavage of the macrocycle. However, EPR study of the synthesized compounds subjected to X-ray irradiation revealed predominant formation of macrocyclic -CH2-ĊH-O- radicals. This result demonstrated an evidence for indirect action of ionizing radiation on individual components of the complexes and was reasonably described by a positive "hole" transfer from primary macrocyclic radical cation to fluorous anion at the primary stages of radiolysis and a subsequent interaction of fluorine atom with 18C6 macrocycle in secondary radical reactions. The observed effects may be partially responsible for enhanced sensitivity of the ionic liquid/crown ether extractants to ionizing radiation due to chemical blocking of the crown ether with radiolytic HF, radiation-chemical degradation of the 18C6, and precipitation of a low-soluble SrF2. © 2018 American Chemical Society