Magnetic investigation of two helical frameworks derived from mixed ligands

Although the 2,2′-biphenyldicarboxylate ligand (2,2′-dpa) has been widely used to construct metal-organic frameworks (MOFs) with helical sub-structure, the effect of the helical arrangement of spin carriers on the magnetic properties remains rarely scarce. In this article, two unique magnetic metal-organic supramolecular frameworks with different structural features, [Cu₂(dpa)₂(H₂O)₂(4,4′-dpdo)_0.5]_n (1) and [Ni(H₂O)₄(dpa)] · (4,4′-dpdo)(H₂O) (2) (dpdo = 4,4′-dipyridine-N,N′-dioxide), have been isolated from the direct reaction of H₂dpa with their corresponding salts in the presence of dpdo. In complex 1, the Cu-dpa double-helical chains, which are bridged by long flexible μ₂-dpdo ligands to give rise to a regular 6³ covalent layer, exhibit strong antiferromagnetic coupling interactions. Whereas the 1D [Ni(dpa)]_n helical chains in complex 2 exhibit weak antiferromagnetic coupling interactions. Rich hydrogen bonds between perpendicular 1D [Ni(dpa)]_n helical chains and quasi-1D (dpdo)_n chains result in an intricate 3D supramolecular network.     

Eu3+-activated red phosphor Ca3YAl3B4O15 with low thermal quenching behaviour

This paper reports a sequence of a Ca₃YAl₃B₄O₁₅:xEu³⁺ red phosphor prepared using a high-temperature solid-state reaction. At the excitation of 396 nm, the samples emitted intense red emission centred at ~623 nm, which could be attributed to the ⁵D₀→⁷F₂ transition of the Eu³⁺ ion. The results showed that the optimum Eu³⁺ doping concentration of Ca₃YAl₃B₄O₁₅:Eu³⁺ phosphor was x = 80 mol%, and the concentration quenching mechanism of Ca₃YAl₃B₄O₁₅:Eu³⁺ red phosphor belonged to the exchange coupling between Eu³⁺ ions. The Commission Internationale de l'éclairage (CIE) coordinates and colour purity of Ca₃Y_0.2Al₃B₄O₁₅:0.8Eu³⁺ were calculated as (0.6375, 0.3476) and 95.5%, respectively. Moreover, the red emission of the obtained phosphor Ca₃YAl₃B₄O₁₅:0.8Eu³⁺ exhibited a low thermal quenching behaviour with an intensity retention rate of 92.85% at 150°C. The above results manifest that the Eu³⁺-activated Ca₃YAl₃B₄O₁₅ phosphor is predicted to be a promising red luminescent component for white light-emitting diodes.     

甘草次酸对Bloom解旋酶生物学特性的影响

甘草次酸(glycyrrhetinic acid,GA)是甘草主要活性组分,可诱导肿瘤细胞凋亡,抑制肿瘤细胞生长.然而,其对BLM解旋酶的抑制作用尚未见报道.本文注视甘草次酸对BLM解旋酶构象、二级结构和生化活性的影响.圆二色光谱和紫外光谱分析显示,GA可破坏BLM642-1290解旋酶α-螺旋结构,改变其构象,并具有2个结合位点.采用荧光偏振技术和自由磷检测证明,GA以浓度依赖的方式抑制BLM642-1290解旋酶与底物dsDNA及ssDNA的结合,抑制BLM642-1290解旋酶活性及ATP酶活性,且抑制类型为混合抑制.综上所述,本文证明GA可通过结合BLM解旋酶,改变BLM解旋酶构象,抑制BLM解旋酶与DNA的结合,从而抑制BLM解旋酶的生化活性.我们的发现将对深入认识GA的抗肿瘤作用有新的启示.     

Surface roughness of denture base and reline materials after disinfection by immersion in chlorhexidine or microwave irradiation

doi: 10.1111/j.1741‐2358.2011.00484.x
Surface roughness of denture base and reline materials after disinfection by immersion in chlorhexidine or microwave irradiation Background: This study evaluated the effect of disinfection by immersion and microwave irradiation on the roughness of one denture base resin (Lucitone‐L) and five relining materials, three hard (Tokuyama Rebase II‐TR, New Truliner‐NT, Ufigel Hard‐UH) and two resilient (Trusoft‐T, Sofreliner‐S). Methods: Fifty specimens were made and divided into groups: CL2 specimens were brushed with 4% chlorhexidine (1 min), immersed in the same solution (10 min) and immersed in water (3 min); MW2 specimens were immersed in water and microwave irradiated (650W; 6 min); CL2 and MW2 specimens were disinfected twice; CL7 and MW7 specimens were submitted to seven cycles using chlorhexidine or microwave irradiation, respectively; W specimens were not disinfected and remained in water (37°C; 7 days). Results: Results were statistically analysed (p = 0.05) and revealed that, at baseline, the highest mean value was observed for T (p < 0.001). Material NT showed increase in roughness after the first (p = 0.003), second (p = 0.001), seventh (p = 0.000) cycles of microwave disinfection and after 7 days of immersion in water (p = 0.033). Conclusions: Resilient liner S presented significant increase in roughness after the second cycle of disinfection with chlorhexidine (p = 0.003). Material T exhibited significantly decreased roughness in group W (p = 0.010), while microwaving produced severe alterations on its surface.     

Electrical effects of potassium and bicarbonate on proximal tubule cells ofNecturus

Summary The effects of stepwise concentration changes of K⁺ and HCO ₃ ^– in the basolateral solution on the basolateral membrane potential (V _bl) of proximal tubule cells of the doubly-perfusedNecturus kidney were examined using conventional microelectrodes. Apparent transference numbers were calculated from changes inV _bl after alterations in external K⁺ concentration from 1.0 to 2.5mm (t _{K, 1.0–2.5}), 2.5 to 10, and in external HCO ₃ ^– concentration (at constant pH) from 5 to 10mm (t _{HCO3, 5–10}), 10 to 20, or 10 to 50.t _{K, 2.5–10} was 0.38±0.02 under control conditions but was sharply reduced to 0.08±0.03 (P>0.001) by 4mm Ba⁺⁺. This concentration of Ba⁺⁺ reducedV _bl by 9±1 mV (at 2.5 external K⁺). Perfusion with SITS (5×10^–4 m) for 1 hr hyperpolarizedV _bl by 10±3 mV and increasedt _{K, 2.5–10} significantly to 0.52±0.01 (P<0.001). Ba⁺⁺ application in the presence of SITS depolarizedV _bl by 22±3 mV. In control conditionst _{HCO3, 10–50} was 0.63±0.05 and was increased to 0.89±0.07 (P<0.01) by Ba⁺⁺ but was decreased to 0.14±0.02 (P<0.001) by SITS. In the absence of apical and basolateral chloride, the response ofV _bl to bicarbonate was diminished but still present (t _{HCO3, 10–20} was 0.35±0.03). Intracellular pH, measured with liquid ion-exchange microelectrodes, increased from 7.42±0.19 to 7.57±0.17 (P<0.02) when basolateral bicarbonate was increased from 10 to 20mm at constant pH. These data show that the effects of bicarbonate onV _bl are largely independent of effects on the K⁺ conductance and that there is a significant current-carrying bicarbonate pathway in the basolateral membrane. Hence, both K⁺ and HCO ₃ ^– gradients are important in the generation ofV _bl, and their relative effects vary reciprocally.     

Expression and characterization of chimeric spidroins from flagelliform-aciniform repetitive modules

Spiders can produce up to seven different types of silks or glues with different mechanical properties. Of these, flagelliform (Flag) silk is the most elastic, and aciniform (AcSp1) silk is the toughest. To produce a chimeric spider silk (spidroin) Flag_R-AcSp1_R, we fused one repetitive module of flagelliform silk from Araneus ventricosus and one repetitive module of aciniform silk from Argiope trifasciata. The recombinant protein expressed in E. coli formed silk-like fibers by manual-drawing. CD analysis showed that the secondary structure of Flag_R-AcSp1_R spidroin remained stable during the gradual reduction of pH from 7.0 to 5.5. The spectrum of FTIR indicated that the secondary structure of Flag_R-AcSp1_R changed from α-helix to β-sheet. The conformation change of Flag_R-AcSp1_R was similar to other spidroins in the fiber formation process. SEM analysis revealed that the mean diameter of the fibers was around 1 ~ 2 μm, and the surface was smooth and uniform. The chimeric fibers exhibited superior toughness (~33.1 MJ/m³) and tensile strength (~261.4 MPa). This study provides new insight into design of chimeric spider silks with high mechanical properties.     

真空渗入转化法中农杆菌在植株体内的分布和活力变化

以真空渗入处理后的白菜植株为材料,采用组织化学染色法和细菌平板培养的方法,研究了农杆菌在植株体内的分布特点及其活力变化。结果表明：不同器官中农杆菌的分布量不同,以花器官中分布最多,叶中次之,茎中最少;农杆菌存在于细胞间隙中,维管束及其周围分布较集中,在胚珠中大量分布。处理后植株体内,各器官中农杆菌的生活力及其数量都随时间延长而减少,但是花器官中的农杆菌存活量较大,处理15d后的花蕾中仍然有一定量(约10.3个CFU/g组织)具有活力的农杆菌存在。讨论了这些研究结果在揭示真空渗入转化法的转化过程和提高转化频率中的意义。     

白杨派杂种无性系生根特性研究

通过对采用杂交育种方法选育出的白杨无性系生根性状进行研究。结果表明,新无性系在最早生根时间、主侧根总数量、主侧根总长度等指标上均存在极显著差异,说明各无性系的生根能力具有显著差异。主根平均根数和侧根平均根数两个性状的遗传方差均大于环境方差,其重复力分别可达95％和87％。进一步分析结果表明易生根的无性系根原基数量最多,平均每段插穗约14．7～7．3个．而较难生根的无性系平均每段插穗约5．5～6．8个,难生根的毛白杨根原基数量最少,平均每段插穗约3．3个。通过层次分析法(AHP)对各无性系生根特性的综合评价结果表明：9606、9603、9608、9607、9614、9610、9602等7个无性系生根能力均优于其亲本和毛白杨。     

Adipocyte differentiation of multipotent cells established from human adipose tissue

In this study multipotent adipose-derived stem cells isolated from human adipose tissue (hMADS cells) were shown to differentiate into adipose cells in serum-free, chemically defined medium. During the differentiation process, hMADS cells exhibited a gene expression pattern similar to that described for rodent clonal preadipocytes and human primary preadipocytes. Differentiated cells displayed the key features of human adipocytes, i.e., expression of specific molecular markers, lipolytic response to agonists of beta-adrenoreceptors (beta2-AR agonist > beta1-AR agonist > beta3-AR agonist) and to the atrial natriuretic peptide, insulin-stimulated glucose transport, and secretion of leptin and adiponectin. hMADS cells were able to respond to drugs as inhibition of adipocyte differentiation was observed in the presence of prostaglandin F2alpha, tumour necrosis factor-alpha, and nordihydroguaiaretic acid, a natural polyhydroxyphenolic antioxidant. Thus, for the first time, human adipose cells with normal karyotype and indefinite life span have been established. They represent a novel and valuable tool for studies of fat tissue development and metabolism.