Synchrotron Radiation Provides a Plausible Explanation for the Generation of a Free Radical Adduct of Thioxolone in Mutant Carbonic Anhydrase II

Thioxolone acts as a prodrug in the presence of carbonic anhydrase II (CA II), whereby the molecule is cleaved by thioester hydrolysis to the carbonic anhydrase inhibitor, 4-mercaptobenzene-1,3-diol (TH0). Thioxolone was soaked into the proton transfer mutant H64A of CA II in an effort to capture a reaction intermediate via X-ray crystallography. Structure determination of the 1.2 ? resolution data revealed the TH0 had been modified to a 4,4'-disulfanediyldibenzene-1,3-diol, a product of crystallization conditions, and a zinc ligated 2,4-dihydroxybenzenesulfenic acid, most likely induced by radiation damage. Neither ligand was likely a result of an enzymatic mechanism.     

Photoinduced charge transfer in porphyrin-C60 oligomer

Photoinduced electron transfer (ET) between C₆₀ and porphyrin (P) in a new polymer containing porphyrin, poly(p-phenylenevinylene), and pendant fullerene units has been investigated by nanosecond transient absorption and phosphorescence spectroscopy. Compared to the physically doping material systems, binding porphyrin/C₆₀ through chemical bonds in a polymer detains the formation of the triplet states of porphyrins and C₆₀. The formation of intermediate charge transfer state (CSS) of P⁺-C₆₀ ^? was observed, which led to the delayed formation of triplet states of porphyrins and C₆₀. The reduced opto-electronic properties, such as optical limiting performance, were also observed, which resulted from the delayed formation of triplet states. The results presented in this article are significant in understanding the complicated spectral characteristics of the triplet state and charge transfer of the porphyrin and C₆₀ complexes, and are therefore related to the controllable performance of the new materials in applications.     

Brain-derived neurotrophic factor protects neurons from GdCl3-induced impairment in neuron-astrocyte co-cultures

Gadolinium (Gd³⁺) complexes are important contrast agents in medical magnetic resonance imaging (MRI) and of great potential value in brain research. In order to better understand the mechanisms of the action of Gd³⁺ on neurons in the complex central nervous system (CNS), the neurotoxic actions of GdCl₃ have been investigated in both neuron monoculture and astrocyte-neuron co-culture systems. Measurements of lactate dehydrogenase release showed that GdCl₃ causes significant cell death of monocultured neurons as a result of reactive oxygen species (ROS) generation and down-regulation of brain-derived neurotrophic factor (BDNF). However, GdCl₃ does not affect the viability and BDNF expression of astrocytes. Both co-culturing of neurons with astrocytes and addition of BDNF ameliorated GdCl₃-induced neurotoxicity by decreasing ROS generation and facilitating recovery of BDNF levels. The results obtained suggest that astrocytes in the CNS may protect neurons from GdCl₃-induced impairment through secreting BDNF and thus up-regulating BDNF expression and interfering with Gd³⁺-induced cell signaling in neurons. A possible molecular mechanism is suggested which should be helpful in understanding the neurotoxic actions of gadolinium probes.     

MgO/Al_2O_3吸附剂对CO_2动态吸附性能的研究

以γ-Al2O3为载体,采用等体积浸渍法制取MgO/Al2O3吸附剂,利用BET、XRD等表征手段对吸附剂进行表征;并通过固定床测量穿透曲线的方法研究其对CO2动态吸附性能的影响,考察了MgO负载量、吸附温度、气体流量等因素对吸附剂吸附CO2性能的影响,同时还通过多次吸脱附实验考察MgO/Al2O3吸附剂的稳定性和再生能力。结果表明,MgO负载量为10%的吸附剂,吸附温度在50℃左右,流量为45 mL/min动态吸附量最大;经数次循环后材料的结构性质和吸附性能未见明显变化,可再生性能比较优异,是一种潜在的可工业化应用的CO2吸附剂。     

无溶剂一锅法Al(ClO_4)_3催化合成α-氨基膦酸酯

以无水高氯酸铝为催化剂,将芳香醛、芳香胺及亚磷酸酯在无溶剂条件下一锅法反应,高效地合成了α-氨基膦酸酯,该催化剂优于其它已发现的催化剂[如Mg(ClO4)2,BiCl3,AlCl3等],建立了一种适用于含有钝化基团的芳香胺的α-氨基膦酸酯的新合成方法.     

7-O-取代-8-甲基香豆素和4H-色烯-4-酮化合物与NBS/CCl_4试剂的溴化反应

7-O-取代-8-甲基香豆素和4-H-色烯-4-酮化合物是合成Seco-DCK和Seco-DCP类似物的重要中间体.报道了在NBS/CCl4条件下,这两类化合物8-位甲基溴代反应的情况.通过实验发现,这两类化合物8-位甲基溴代反应较一般芳环苄位的溴代更为复杂,存在多个反应位点.影响8-位甲基溴代选择性和收率的主要因素有三:邻位基团空间位阻大小、自由基引发催化剂的使用与否以及邻位基团的电性因素.通过控制反应条件,可以中等收率得到8-位甲基溴代化合物.     

Construction of two fluorescence‐labeled non‐combined DNA index system miniSTR multiplex systems to analyze degraded DNA samples in the Chinese Han Population

MiniSTR loci have been demonstrated to be an effective approach in recovering genetic information from degraded specimens, because of the reduced PCR amplicon sizes which improved the PCR efficiency. Eight non‐combined DNA index system miniSTR loci suitable for the Chinese Han Population were analyzed in 300 unrelated Chinese Han individuals using two novel five fluorescence‐labeled miniSTR multiplex systems(multiplex I: D10S1248, D2S441, D1S1677 and D9S2157; multiplex II: D9S1122, D10S1435, D12ATA63, D2S1776 and Amelogenin). The allele frequency distribution and forensic parameters in the Chinese Han Population were reported in this article. The Exact Test demonstrated that all loci surveyed here were found to be no deviation from Hardy–Weinberg equilibrium. The accumulated power of discrimination and power of exclusion for the eight loci were 0.999999992 and 0.98, respectively. The highly degraded DNA from artificially degraded samples and the degraded forensic case work samples was assessed with the two miniSTR multiplex systems, and the results showed that the systems were quite effective.     

Study on the influence of cross-sectional area and zeta potential on separation for hybrid-chip-based capillary electrophoresis using 3-D simulations

Hybrid chips combing microchips with capillaries have displayed particular advantages in achieving UV-vis and mass spectroscopic detection. In this work, systematic 3-D numerical simulations have been carried out to explore the influence of junction interface cross-sectional area and ζ-potential distribution on sample band broadening in hybrid-chip electrophoresis separation. In this case, the ratio of cross-sectional area of chip to capillary channel (S(ratio) ) is used as the parameter of the variation in junction interface cross-sectional area. Theoretical simulations demonstrated that the decrease of the S(ratio) would increase the separation efficiency in the hybrid-chip-based CE with uniform ζ-potential distribution. ζ-potential distribution along the axial direction of the channel also affects mass transport in hybrid-chip-based CE. Therefore, the effect of ζ-potential distribution has been considered in the 3-D simulation. Theoretical simulation results reveal that ζ-potential distribution rather than the interface cross-sectional area variation (S(ratio) ) controls the sample band broadening and manipulates sample separation efficiency in the hybrid-chip-based CE with non-uniform ζ-potential distribution. Both the theoretical simulations and experimental results show that optimal hybrid-chip CE separation efficiency can be achieved at S(ratio) =1.     

Chiral Brønsted Acid Directed Iron‐Catalyzed Enantioselective Friedel–Crafts Alkylation of Indoles with β‐Aryl α′‐Hydroxy Enones

A cooperative catalytic system established by the combination of an iron salt and a chiral Brønsted acid has proven to be effective in the asymmetric Friedel–Crafts alkylation of indoles with β‐aryl α′‐hydroxy enones. Good to excellent yields and enatioselectivities were observed for a variety of α′‐hydroxy enones and indoles, particularly for the β‐aryl α′‐hydroxy enones bearing an electron‐withdrawing group at the para position of the phenyl ring (up to 90 % yield and 91 % ee). The proton of the chiral Brønsted acid, the Lewis acid activation site, as well as the inherent basic site for the hydrogen‐bonding interaction of the Brønsted acid are responsible for the high catalytic activities and enantioselectivities of the title reaction. A possible reaction mechanism was proposed. The key catalytic species in the catalytic system, the phosphate salt of Fe^III, which was thought to be responsible for the high activity and good enantioselectivity, was then confirmed by ESIMS studies.     

2,3,7,8,12,13‐Hexaaryltruxenes: An ortho‐Substituted Multiarm Design and Microwave‐Accelerated Synthesis toward Starburst Macromolecular Materials with Well‐Defined π Delocalization

We present herein a novel design and the efficient synthesis towards a “homogeneous” starburst fluorene system based on the novel 2,3,7,8,12,13‐hexaaryltruxene scaffold. Controlled microwave heating provides a facile and powerful approach for each step in the synthesis of these bulky materials with large steric hindrance, suggesting an avenue to access structurally well‐defined complex organic semiconductors (OSCs) rapidly and conveniently with high yield and purity. The resulting materials exhibited good thermal stability and an excellent glassy structure as revealed by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) as well as wide‐angle X‐ray diffraction (WAXD) studies. Moreover, compared with their corresponding three‐arm‐substituted counterparts T1 – T4 , the introduction of the ortho substituents around the truxene core in Tr1 – Tr4 results in significant blueshifts (of 7–24 nm) of the absorption maxima λ_max and higher energy optical gaps (E_g). Comparative studies with corresponding linear, rod‐shaped oligofluorene counterparts (OFX) have revealed that the longest para‐conjugated segment in the TrX (X=1–4) structures plays the dominant role in determining their electronic properties. UV/Vis data and cyclic voltammetry (CV) investigations have indicated that there is little electronic interaction between the arms, even for the shortest armed oligomer Tr1 . A clear linear relationship of both 1/λ_max and E_g with the inverse of (n+1) for these branched systems was found. Our findings highlight a novel molecular design comprising an ortho‐substituted, multiarmed architecture that would allow the introduction of isotropic physical and/or mechanical properties, while at the same time maintaining most of the important electronic properties of the rod‐shaped constituents of a fully conjugated system.