Synthesis,structural characterization,and anion interactions of new triazole-linked urea derivative fully substituted cyclotriphosphazene compounds

Three novel fully substituted urea derivative cyclotriphosphazene compounds 5–7 were synthesized by alkyne-azide 1,3-dipolar cycloaddition reaction of propargyl substituted ureas 2–4 with hexaazide substituted cyclotriphosphazene 1 in the presence of Cu(I) catalyst. All compounds were characterized with spectroscopic techniques such as FT-IR, ¹H, ¹³C, and ³¹P nuclear magnetic resonance and mass spectroscopy. Also, the usefulness of compounds 5–7 as anion carriers was investigated by ¹H NMR spectroscopy. For this purpose, ¹H NMR spectra of compounds 5–7 were recorded in the presence of tetrabutylammonium fluoride in DMSO-d₆. It was determined, that the urea protons in the compounds interact with fluoride.     

Mild Palladium Catalyzed ortho C‐H Bond Functionalizations of Aniline Derivatives

This account collects the developments and transformations which avoid the utilization of harsh reaction conditions in the field of palladium catalyzed, ortho‐directed C?H activation of aniline derivatives from the first attempts to up‐to‐date results, including the results of our research laboratory. The discussed functionalizations performed under mild conditions include acylation, olefination, arylation, alkylation, alkoxylation reactions. Beside the optimization studies and the synthetic applications mechanistic investigations are also presented.     

Starch Derived Nanosized Graphene Oxide Functionalized Bioactive Porous Starch Scaffolds

A fully starch‐derived bioactive 3D porous scaffold is developed. The bioactivity is introduced through nanosized graphene oxide (nGO) derived from starch by microwave‐assisted degradation to carbon spheres and further oxidation to GO nanodots. nGO is covalently attached to starch to prepare functionalized starch (SNGO) via an esterification reaction. nGO and SNGO exhibit no cytotoxicity to MG63 at least up to 1000 µg mL⁻¹ under (3‐(4,5‐Dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide) assay. Porous scaffolds consisting of starch and SNGO (S/SNGO) or nGO (S/nGO) are prepared by freeze drying. The porosity and water uptake ability of the scaffolds depend on the concentration of nGO. Moreover, nGO, as a bioactive nanofiller, functions as an effective anchoring site for inducing CaP recrystallization in simulated body fluid. Among all modified starch‐based scaffolds, the S/SNGO scaffold containing the highest concentration of covalently attached SNGO (50%) induces the largest amount of hydroxyapatite, a type of CaP crystal that is closest to bone. The prepared 3D porous nGO functionalized scaffold, thus, exhibits potential promise for bone/cartilage tissue engineering.

     

N-[5-(Е)-1,3,4-噻二唑-2-基]-N'-芳基脲的合成、晶体结构及生物活性

为了寻找高活性的脲类细胞分裂素,通过2-氨基-5-(Е)-苯乙烯基-1,3,4-噻二唑与芳酰基叠氮化物反应,合成了11种新的含1,3,4-噻二唑环芳基脲类衍生物,其中芳酰基叠氮化物直接由芳酸、三氯氧磷与叠氮钠采用"一锅法"制得,再经加热发生Curtius重排转化为异氰酸酯.目标化合物的结构用红外光谱、核磁共振氢谱、质谱和元素分析进行了表征,并用X射线单晶衍射实验测定了化合物3g的结构.初步的生物活性测试表明,部分目标化合物在10 mg/L浓度下表现出良好的细胞分裂素活性,其中3c的活性超过50%.     

以尿素为氮源制备氮改性二氧化钛及其改性机理

以钛酸丁酯为前驱体,以尿素为氮源,采用改进溶胶-凝胶法制备了不同N含量的改性TiO2光催化剂(N-TiO2).以重铬酸钾为目标污染物,以甲酸为空穴捕获剂,评价了可见光下该催化剂的催化还原活性.结果表明,N-TiO2催化剂活性明显高于未改性催化剂,当催化剂中N/Ti摩尔比为10%、焙烧温度为400℃时,其光催化还原活性最...     

Self-assembly approach toward chiral bimetallic catalysts: bis-urea-functionalized (salen)cobalt complexes for the hydrolytic kinetic resolution of epoxides

A series of novel bis-urea-functionalized (salen)Co complexes has been developed. The complexes were designed to form self-assembled structures in solution through intermolecular urea-urea hydrogen-bonding interactions. These bis-urea (salen)Co catalysts resulted in rate acceleration (up to 13 times) in the hydrolytic kinetic resolution (HKR) of rac-epichlorohydrin in THF by facilitating cooperative activation, compared to the monomeric catalyst. In addition, one of the bis-urea (salen)Co(III) catalyst efficiently resolves various terminal epoxides even under solvent-free conditions by requiring much shorter reaction time at low catalyst loading (0.03-0.05 mol %). A series of kinetic/mechanistic studies demonstrated that the self-association of two (salen)Co units through urea-urea hydrogen bonds was responsible for the observed rate acceleration. The self-assembly study with the bis-urea (salen)Co by FTIR spectroscopy and with the corresponding (salen)Ni complex by (1)H NMR spectroscopy showed that intermolecular hydrogen-bonding interactions exist between the bis-urea scaffolds in THF. This result demonstrates that self-assembly approach by using non-covalent interactions can be an alternative and useful strategy toward the efficient HKR catalysis.     

Key players and their role during mitochondrial iron-sulfur cluster biosynthesis

Iron-sulfur clusters are multifaceted iron-containing cofactors coordinated and utilized by numerous proteins in nearly all biological systems. Fe-S-cluster-containing proteins help direct pathways essential for cell viability and participate in biological applications ranging from nucleotide biosynthesis and stability, protein translation, enzyme catalysis, and mitochondrial metabolism. Fe-S-containing proteins function by utilizing the unique electronic and chemical properties inherent in the Fe containing cofactor. Fe-S clusters are constructed of inorganic iron and sulfide arranged in a distinct caged structural makeup ranging from [Fe(2) -S(2) ], [Fe(3) -S(4) ], [Fe(4) -S(4) ], up to [Fe(8) -S(8) ] clusters. In eukaryotes, cluster activity is controlled in part at the assembly level and the major pathway for cluster production exists within the mitochondria. Recent insight into the pathway of mitochondrial cluster assembly has come from new in vivo and in vitro reports that provided direct insight into how all protein partners within the assembly pathway interact. However, we are only just beginning to understand the role of each protein within this complex pageant that is mitochondrial Fe-S cluster assembly. In this report we present results, using the yeast model for mitochondrial assembly, to describe the molecular details of how important proteins in the pathway coordinate for cluster assembly.     

The biological characteristics of different generation mesenchymal stem cells cultured in vitro and cocultured with vascular scaffold

Mesenchymal stem cells (MSCs) were used widely as seed cells in tissue engineering blood vessel construction. However, the biological characteristics difference of different generation MSCs in vitro culture is unknown, which laid a foundation for appropriate generation seeded cells selection for tissue engineering blood vessel construction. In this report, MSCs were isolated from SD rat bone marrow and identified by flow cytometry; cell growth curve test, cell surface antigen expression rate detection, cryopreservation resuscitation rate test, CD31 expression rate test, cell cycle analysis, and adhesion difference on vascular scaffold test were performed. The research results indicated that the MSCs shape was spindle and uniform with vigorous growth. CD105 and CD90 factor expression rate reached 82.5 and 84.9%, respectively, and the expression rate of CD45 was only 7.3%. The proliferation capacity of the fourth generation MSCs were more exuberant, with proliferation index as 20.3%; the cell proliferation index of the eighth generation decreased to only 9.1%. The cryopreservation resuscitation rate of the second generation and fourth generation MSCs were both higher than 80%, and the cryopreservation resuscitation rate of the eighth generation MSCs was only about 60%. After the induction for 5 days, MSCs had weak CD31 expression, and with the prolonged induction time, expression increased. All generation MSCs expressed CD31 after being induced for 10 days; however, the CD31 positive expression rate of the second generation, fourth generation, and sixth generation MSCs had significant difference with the eighth generation MSCs. Adhesion rate of MSCs before sixth generation was around 40%, but the adhesion rate of eighth generation MSCs was only about 27%. In all, biological characteristics of different generation MSCs existed certain differences, and especially the eighth generation MSCs aged seriously, whose cell activity decreased significantly. The researchers believed that the MSCs before the sixth generation can maintain excellent properties of MSCs, and can be used as seed cells for vascular tissue engineering.