漫湾库区景观破碎化对区域生境质量的影响

水利工程的建设不仅改变了库区的景观格局,还会导致区域生物生境质量的变化。以澜沧江漫湾库区为例,在综合海拔高度、植被类型和水源地距离生境因子的基础上,考虑生物扩散过程,研究了建坝前后整个库区以及典型研究小区(库首、库中、库尾、对照)的重要生境斑块空间分布变化。结果表明:漫湾水电站建成后库区的猕猴总体生境破碎化程度增加,景观连接度减少且重要生境斑块的比例也有所降低,生境质量整体下降;4个研究小区的景观格局变化情况同整个库区相一致。空间上,生境质量明显退化的地区主要分布在库区的西部和南部,尤其是库尾地区,其生境斑块数量相较于建坝前增长了9倍,而景观连接度指数下降了81.48%。回归分析结果表明景观连接度指数与占景观面积百分比指数(PLAND)呈显著正相关(R~2=0.973),与斑块数(NP)呈显著负相关(R~2=-0.611);肯德尔系数表明斑块数(NP)、最大斑块指数(LPI)、占景观百分比指数(PLAND)、相似邻近百分比指数(PLADJ)、连通度指数(CONNECT)和香农多样性指数(SHDI)7个景观格局指数与景观连接度指数均表现出显著一致性。由此看出,库区景观破碎化越严重、区域景观连接度越低生境质量退化越明显;而提高生境主要植被类型的覆盖率、保护连接度贡献大的重要斑块和建设生态廊道,可以有效恢复库区生物生境质量。     

Three-dimensional structure of manganese superoxide dismutase from Bacillus halodenitrificans,a component of the so-called "green protein"

A so-called "green protein" has been purified from a moderate halophilic eubacterium, Bacillus halodenitrificans (ATCC 49067), under anaerobic conditions. The protein, which might play an important role in denitrification, dissociates mainly into two components after exposure to air: a manganese superoxide dismutase (GP-MnSOD) and a nucleoside diphosphate kinase. As a first step in elucidating the overall structure of the green protein and the role of each component, the 2.8-A resolution crystal structure of GP-MnSOD was determined. Compared with other manganese dismutases, GP-MnSOD shows two significant characteristics. The first is that the entrance to its substrate channel has an additional basic residue-Lys38. The second is that its surface is decorated with an excess of acidic over basic residues. All these structural features may be related to GP-MnSOD's high catalytic activity and its endurance against the special cytoplasm of B. halodenitrificans. The structure of GP-MnSOD provides the basis for recognizing its possible role and assembly state in the green protein.     

钮子七提取物的抗氧化作用及对胃癌细胞的抑制作用

以钮子七提取物为材料,通过邻苯三酚自氧化法测定钮子七提取物对超氧阴离子生成的影响,通过邻二氮菲溶液测定钮子七提取物对羟自由基的清除作用;采用噻唑蓝(MTT)法测定钮子七提取物对胃癌细胞生长的影响。结果显示,钮子七水提取物和70%乙醇提取物对超氧阴离子的产生有较强的抑制作用,在浓度大于5.0 mg/m L时,抑制作用显著增强。钮子七70%乙醇提取物和水提取物均有清除羟自由基的作用,在浓度大于2.5 mg/m L时清除作用显著增强。钮子七水提物和乙酸乙酯提取物在24 h、48 h及72 h后对胃癌细胞均有抑制作用,且都以作用72 h后抑制作用最强。结果表明,钮子七提取物具有较强的抗氧化作用以及较强的抑制胃癌细胞的作用。     

毕赤酵母表达gp96-scFv抗体及生物活性测定

旨在利用毕赤酵母分泌表达gp96-scFv抗体,纯化后得到能特异性结合gp96抗原的小分子抗体片段(scFv)。根据gp96-scFv抗体基因序列,合成gp96-scFv抗体基因序列,将gp96-scFv抗体序列克隆到毕赤酵母表达质粒pPICZα-A,线性化的重组表达载体电转化到毕赤酵母X33,甲醇诱导目的蛋白表达,通过亲和层析法纯化目的蛋白,并以SDS-PAGE和Western blotting进行鉴定。通过Western blotting、Immunofluorescence、ELISA、FACS方法对gp96-scFv抗体的生物活性进行了检测。结果成功地构建了分泌表达抗gp96蛋白scFv抗体的毕赤酵母菌,每升毕赤酵母菌培养上清经纯化可获约50 mg gp96-scFv抗体,所获抗体其分子量大约为15 kDa,具有与gp96抗原特异性结合的活性。本研究通过毕赤酵母菌成功表达了gp96-scFv抗体,生物活性Western blotting、Immunofluorescence、ELISA、FACS分析表明该抗体能特异性结合gp96。     

Activity Characteristics and Tyrosinase Inhibition Mechanism of a Silk Fibroin Oligopeptide and Cordyceps Polysaccharide Composite

International Journal of Peptide Research and Therapeutics - Silk fibroin is an excellent raw material for medical products as it shows remarkable biocompatibility, water-based processing, and...     

Rapamycin inhibits AR signaling pathway in prostate cancer by interacting with the FK1 domain of FKBP51

Reactivation of the androgen receptor signaling pathway in the emasculated environment is the main reason for the occurrence of castration-resistant prostate cancer (CRPC). The immunophilin FKBP51, as a co-chaperone protein, together with Hsp90 help the correct folding of AR. Rapamycin is a known small-molecule inhibitor of FKBP51, but its effect on the FKBP51/AR signaling pathway is not clear. In this study, the interaction mechanism between FKBP51 and rapamycin was investigated using steady-state fluorescence quenching, X-ray crystallization, MTT assay, and qRT-PCR. Steady-state fluorescence quenching assay showed that rapamycin could interact with FKBP51. The crystal of the rapamycin-FKBP51 complex indicated that rapamycin occupies the hydrophobic binding pocket of FK1 domain which is vital for AR activity. The residues involving rapamycin binding are mainly hydrophobic and may overlap with the AR interaction site. Further assays showed that rapamycin could inhibit the androgen-dependent growth of human prostate cancer cells by down-regulating the expression levels of AR activated downstream genes. Taken together, our study demonstrates that rapamycin suppresses AR signaling pathway by interfering with the interaction between AR and FKBP51. The results of this study not only can provide useful information about the interaction mechanism between rapamycin and FKBP51, but also can provide new clues for the treatment of prostate cancer and castration-resistant prostate cancer.