Comparison of interactions between human serum albumin and silver nanoparticles of different sizes using spectroscopic methods

Three different sizes (15.9 ± 2.1 nm, 26.4 ± 3.2 nm and 39.8 ± 4.0 nm, respectively) of citrate‐coated silver nanoparticles (SNPs) have been synthesized and characterized. The interactions of the synthesized SNPs with human serum albumin (HSA) at physiological pH have been systematically studied by UV‐vis absorption spectroscopy, fluorescence spectroscopy, synchronous fluorescence spectroscopy, three‐dimensional fluorescence spectroscopy and circular dichroism (CD) spectroscopy. The results indicate that the SNPs can bind to HSA with high affinity and quench the intrinsic fluorescence of HSA. The binding constants and quenching rate constants were calculated. The apparent association constants (K_app) values are 2.14 × 10⁴ M^–1 for 15.9 nm SNP, 1.65 × 10⁴ M^–1 for 26.4 nm SNP and 1.37 × 10⁴ M^–1 for 39.8 nm SNP, respectively. The values of binding constant obtained from the fluorescence quenching data match well with that determined from the absorption spectral changes. These results suggest that the smaller SNPs have stronger interactions to HSA than the larger ones at the same concentrations. Synchronous fluorescence, three‐dimensional fluorescence and CD spectroscopy studies show that the synthesized SNPs can induce slight conformational changes in HSA. Copyright © 2014 John Wiley & Sons, Ltd.     

植物根负向光性反应

本文介绍植物根的负向光性反应研究现状和进展。     

鄂东大别山国家重点保护野生植物优先保护定量研究

在野外调查的基础上,运用濒危系数、遗传价值系数和物种价值系数对鄂东大别山18种国家重点保护野生植物的优先保护顺序进行定量分析。结果表明属一级保护的有银杏、南方红豆杉、大别山五针松、金钱松、巴山榧树、连香树和楠木共7种,占38.9%;属二级保护的有秤锤树、喜树、香果树、鹅掌楸和川黄檗共5种,占27.8%;属三级保护的有厚朴、凹叶厚朴和榉树3种,占16.7%;属四级保护的有樟树、野大豆和金荞麦共3种,占16.7%。并提出了加强国家重点保护野生植物的保护措施。     

Monogenea from the middle Yangtze Valley: Sinomazocraes changjiangensis n. g., n. sp. (Family Mazocraeidae Price, 1936) on a clupeiform fish from Hubei Province,China

Sinomazocraes changjiangensis n. g., n. sp. (Monogenea: Mazocraeidae) is described from the gills of the shortjaw tapertail anchovy Coilia brachygnathus collected from Jiayu and Huanggang Counties (Hubei Province), which are located in the middle reaches of the Yangtze River. The structure of the clamps and copulatory organ are similar to those of Heteromazocraes Mamaev, 1981. However, although Sinomazocraes also has four pairs of clamps, it is distinguished from other genera in the family by the fact that the three anterior clamps on one side of the body are significantly larger than the others. Variations in the form of the clamps in different species of the Mazocraeidae are discussed.     

Impact of extreme drought on tree-ring width and vessel anatomical features of Chukrasia tabularis

Multiple sources of evidence suggest an increasing frequency of extreme climatic events during the past century. In Bangladesh, a country strongly influenced by the South Asian monsoon climate, the years 1999 and 2006 were the most severe droughts among the ten drought events identified over the last four decades. We investigated the impact of these two drought events on radial growth and xylem anatomical features of the brevi-deciduous tree species Chukrasia tabularis in a moist tropical forest in Bangladesh. Tree radial growth declined by 54% during the 1999 and 48.7% during the 2006 droughts, respectively. Among the wood anatomical features, the number of vessels (NV) showed the highest sensitivity to drought, with a 45% decrease in the 1999 drought year, followed by total vessel area (TVA) and mean vessel area (MVA). On the other hand, Vessel density (VD) increased by 13% during the 1999 drought but the increase in VD was very low in the drought year 2006. The decreasing vessel area and increasing vessel density indicate xylem hydraulic adaptation of C. tabularis to minimize drought induced cavitation risk and to avoid hydraulic failure. The significant correlations between the Standardized Precipitation Evapotranspiration Index (SPEI) and time series of tree-ring width and vessel variables imply that decline in radial growth and changes in vessel features in C. tabularis are likely to be caused by drought induced water stress. Our analyses suggest that radial growth and wood anatomical features of C. tabularis are highly sensitive to extreme drought events in South Asian moist tropical forests and can be used to reconstruct past droughts and to model tree response to drought stress under future climate conditions.     

湖北省直翅目三新种(直翅目)

记述采自湖北省九宫山及武当山地区直翅目昆虫3新种,即橙股卵翅蝗Caryanda byrrhofemura,sp．nov．,九宫山澳汉蚱Austrohancokia jiugongshanensis,sp.nov.及幕阜山台蚱Formosatettix mufushanensis,sp.nov．。此外记述贺兰台蚱Formosatettix helanshanensis Zheng的雄性。     

Translational suppression by hammerhead ribozymes and inactive variants in S. cerevisiae

The activity of hammerhead ribozymes in S. cerevisiae was assessed using two ribozymes that were designed to intramolecularly attack the hepatitis B viral X mRNA. The ribozymes effectively suppressed the expression of the X-lacZ fusion gene, when they were inserted at the 5′ end of the X mRNA. The ribozymes cleaved the target RNA efficiently at the targeted phosphodiester bond, but the inactive mutants carrying G5-to-A substitution in the core did not, as the total RNA preparations of yeast extracts was assayed by primer extension. These G5A mutants, however, exerted the suppression as effectively as the wild-type ribozymes. The results, with several mutations introduced to a ribozyme, suggested that either mere formation of hammerhead-like structures with the three stems, or the formation of any two stems, could inhibit translation. Thus, the hammerhead-like structures, leading to cleavage or not, could effectively suppress translation, especially when formed around the initiation codon. The G5-to-A and U7-to-G mutations and replacement of the stem-II hairpin tetraloop did not appear to affect the formation of the inhibitory structure(s). The inhibition that was observed when stems I and III were directly connected without a loop or with a stem II hairpin was completely relieved when they were connected with only the loop of stem II (not containing the stem portion).