Simultaneous determination of ascorbic acid,dopamine and uric acid based on tryptophan functionalized graphene

A new type of tryptophan-functionalized graphene nanocomposite (Trp-GR) was synthesized by utilizing a facile ultrasonic method via π–π conjugate action between graphene (GR) and tryptophan (Trp) molecule. The material as prepared had well dispersivity in water and better conductivity than pure GR. The surface morphology of Trp-GR was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. The electrochemical behaviors of ascorbic acid (AA), dopamine (DA), and uric acid (UA) were investigated by cyclic voltammetry (CV) on the surface of Trp-GR. The separation of the oxidation peak potentials for AA–DA, DA–UA and UA–AA was about 182 mV, 125 mV and 307 mV, which allowed simultaneously determining AA, DA, and UA. Differential pulse voltammetery (DPV) was used for the determination of AA, DA, and UA in their mixture. Under optimum conditions, the linear response ranges for the determination of AA, DA, and UA were 0.2–12.9 mM, 0.5–110 μM, and 10–1000 μM, with the detection limits (S/N = 3) of 10.09 μM, 0.29 μM and 1.24 μM, respectively. Furthermore, the modified electrode was investigated for real sample analysis.     

N-Alkoxymethylation of heterocyclic compounds with diethyl phosphite via cleavage of P-O bond

N-Alkoxymethylation of heterocyclic compounds with diethyl phosphite via cleavage of P-O bond was investigated and a series of N3-ethoxymethylated heterocyclic compounds were synthesized. A mechanism in which diethyl phosphite acts as an efficient surrogate of ethanol was proposed and supported by several evidences.     

Synthesis of C2-functionalized pyrimidines from 3,4-dihydropyrimidin-2(1H)-ones by the Mitsunobu coupling reaction

The Biginelli 3,4-dihydropyrimidin-2(1H)-one was converted to various C2-multifunctionalized pyrimidines via the dehydrogenation and Mitsunobu reaction using amines, alcohols, phenols and carboxylic acids as nucleophiles. A possible mechanism was also proposed to rationalize the formation of products.     

新型对称联苯双酯类液晶材料的合成和晶体结构

设计并合成了4个对称联苯双酯类液晶化合物,化合物结构通过红外和核磁表征,它们的介晶性通过差示扫描量热仪(DSC),X射线衍射仪(XRD)和热台偏光显微镜(POM)进行了研究.并测定了4,4'-3,3',5,5'-四甲基联苯-二(4-甲基苯甲酸酯)(Ⅲa)的单晶结构,结果显示:晶体属于单斜晶系,P21/c空间群,晶胞参数为a=18.525(3)(A),b=12.196(2)(A),c=12.195(2)(A),β=97.142(2)°,V=2733.7(9)(A)3,Z=4,Dc=1.163 Mg/m3,R=0.0521,Rw=0.1161.化合物均为热致型互变液晶,并讨论了氧原子、不饱和端基和端基链长对介晶性的影响.     

Synthesis,structure, and DNA-binding properties of manganese(II) and zinc(II) complexes with tris(<Emphasis Type="Italic">N</Emphasis>-methylbenzimidazol-2-ylmethyl)amine ligand

Tris(N-methylbenzimidazol-2-ylmethyl)amine (Mentb) and its two complexes, [Mn(Mentb)(DMF)(H₂O)](pic)₂ 1 and [Zn(Mentb)(pic)](pic) 2 (pic = picrate), have been synthesized and characterized by physico-chemical and spectroscopic methods. Single crystal X-ray diffraction revealed that the two complexes have different structures. In complex 1, the coordination sphere around Mn(II) is distorted octahedral, whereas in complex 2 the coordination sphere around Zn(II) is distorted trigonal bipyramidal. The DNA-binding properties of the free ligand and its two complexes have been investigated by electronic absorption, fluorescence, and viscosity measurements. The results suggest that the ligand and its two complexes bind to DNA via an intercalation binding mode, and their binding affinity for DNA follows the order 1 > 2 > ligand.     

A Schiff base ligand <Emphasis Type="Italic">N</Emphasis>-(2-hydroxylacetophenone)-3-oxapentane-1,5-diamine and its nickel(II) complex: synthesis,crystal structure,antioxidation, and DNA-binding properties

A new Schiff base ligand N-(2-hydroxylacetophenone)-3-oxapentane-1,5-diamine (HL) and its Ni complex, [Ni₂(L)₂(NO₃)₂], have been synthesized and characterized by physicochemical and spectroscopic methods. The X-ray crystal structure of [Ni₂(L)₂(NO₃)₂] shows it to be a dinuclear 2:2 complex, in which each Ni(II) atom is in a distorted octahedral geometry. The two Ni(II) atoms are dibridged by two phenoxo ligands, forming a Ni₂O₂ parallelogram-type moiety. The interactions between free HL and the complex with calf thymus DNA have been investigated, and the binding constant and linear Stern–Volmer quenching constant suggest that the two compounds bind to DNA via the intercalation mode. The binding affinity of the complex was higher than that of HL. Antioxidant assays in vitro showed that the Ni(II) complex possesses significant antioxidant activity.     

Synthesis of phosphates and phosphates-acetates hybrids of green tea polyphenol (−)-epigallocatechine-3-gallate (EGCG) and its G ring deoxy analogs as potential anticancer prodrugs

A series of phosphate or phosphate-acetate hybrid modified EGCG or EGCG G ring deoxy analogs were synthesized by a convenient semi-synthesis strategy from the abundant natural compound EGCG.     

Induction of a High-Yield Lovastatin Mutant of Aspergillus terreus by 12C6+ Heavy-Ion Beam Irradiation and the Influence of Culture Conditions on Lovastatin Production Under Submerged Fermentation

Heavy-ion beams, possessing a wide mutation spectrum and increased mutation frequency, have been used effectively as a breeding method. In this study, the heavy-ion beams generated by the Heavy-Ion Research Facility in Lanzhou were used to mutagenize Aspergillus terreus CA99 for screening high-yield lovastatin strains. Furthermore, the main growth conditions as well as the influences of carbon and nitrogen sources on the growth and the lovastatin production of the mutant and the original strains were investigated comparatively. The spores of A. terreus CA99 were irradiated by 15, 20, 25, and 30 Gy of 80 MeV/u (12)C(6+) heavy-ion beams. Based on the lovastatin contents in the fermentation broth, a strain designated as A. terreus Z15-7 has been selected from the clone irradiated by the heavy-ion beam. When compared with the original strain, the content of lovastatin in the fermentation broth of A. terreus Z15-7 increased 4-fold. Moreover, A. terreus Z15-7 efficiently used the carbon and nitrogen sources for the growth and production of lovastatin when compared to the original strain. The maximum yield of lovastatin, 916.7 μg/ml, was obtained as A. terreus Z15-7 was submerged cultured in the chemically defined medium supplemented with 3% glycerol as a carbon source, 1% corn meal as an organic nitrogen source, and 0.2% sodium nitrate as an inorganic nitrogen source at 30 °C in the shake flask. The result shows that heavy-ion beam irradiation is an effective method for the mutation breeding of lovastatin production of A. terreus.     

Ce掺杂Mn3O4及其电化学电容行为

用溶胶-凝胶方法合成了Mn₃O₄和Ce掺杂Mn₃O₄. 采用X射线衍射(XRD)、傅里叶变换红外(FT-IR)光谱、场发射扫描电镜(FESEM)和透射电子显微镜(TEM)对其结构和形貌进行了表征. 采用循环伏安、电化学交流阻抗和恒流充放电技术对其电化学性能进行了测试. 研究结果表明, Ce掺杂对Mn₃O₄的形貌和电化学性能均有显著影响. 当Ce离子占金属离子总量的3%时, 掺杂Mn₃O₄的单电极比电容高达477 F·g^-1, 比未掺杂的提高了43.7%, 并且表现出更好的循环稳定性.     

Density functional theory study of the mechanism of the acid-catalyzed decarboxylation of pyrrole-2-carboxylic acid and mesitoic acid

The mechanisms of the acid-catalyzed decarboxylation of pyrrole-2-carboxylic acid and mesitoic acid have been investigated based on density functional theory calculations at the B3LYP/6-311G (d,p) level. A polarizable continuum model (PCM) has been established in order to evaluate the effects of solvents on these reactions. The results of the calculations indicate that the first step of the acid-catalyzed decarboxylation of the pyrrole-2-carboxylic acid has two possible pathways,that is,the proton of H3O+ a...