Cd对蒌蒿生理生化及叶片超微结构的影响

采用Cd砂土污染试验,研究了Cd对蒌蒿生理生化特征及叶片超微结构的影响,结果表明在砂土Cd含量>180mg/kg,蒌蒿出现中毒症状,叶绿素含量、a/b值、POD含量均下降,MDA积累,膜质过氧化,叶绿体形状球形化、片层结构解体、双层膜边界模糊、嗜锇颗粒增多,细胞核形状凹陷,核质分布不均匀、染色质凝胶化。低于180mg/kg的砂土Cd浓度,蒌蒿的上述生理生化指标和叶片超微结构基本正常。蒌蒿可以耐受的Cd浓度不超过180mg/kg。     

Regio- and Stereospecificity of Filipin Hydroxylation Sites Revealed by Crystal Structures of Cytochrome P450 105P1 and 105D6 from Streptomyces avermitilis

The polyene macrolide antibiotic filipin is widely used as a probe for cholesterol and a diagnostic tool for type C Niemann-Pick disease. Two position-specific P450 enzymes are involved in the post-polyketide modification of filipin during its biosynthesis, thereby providing molecular diversity to the “filipin complex.” CYP105P1 and CYP105D6 from Streptomyces avermitilis, despite their high sequence similarities, catalyze filipin hydroxylation at different positions, C26 and C1′, respectively. Here, we determined the crystal structure of the CYP105P1-filipin I complex. The distal pocket of CYP105P1 has the second largest size among P450 hydroxylases that act on macrolide substrates. Compared with previously determined substrate-free structures, the FG helices showed significant closing motion on substrate binding. The long BC loop region adopts a unique extended conformation without a B′ helix. The binding site is essentially hydrophobic, but numerous water molecules are involved in recognizing the polyol side of the substrate. Therefore, the distal pocket of CYP105P1 provides a specific environment for the large filipin substrate to bind with its pro-S side of position C26 directed toward the heme iron. The ligand-free CYP105D6 structure was also determined. A small sub-pocket accommodating the long alkyl side chain of filipin I was observed in the CYP105P1 structure but was absent in the CYP105D6 structure, indicating that filipin cannot bind to CYP105D6 with a similar orientation due to steric hindrance. This observation can explain the strict regiospecificity of these enzymes.     

Crystal Structures of Cytochrome P450 105P1 from Streptomyces avermitilis: Conformational Flexibility and Histidine Ligation State

The polyene macrolide antibiotic filipin is widely used as a probe for cholesterol in biological membranes. The filipin biosynthetic pathway of Streptomyces avermitilis contains two position-specific hydroxylases, C26-specific CYP105P1 and C1′-specific CYP105D6. In this study, we describe the three X-ray crystal structures of CYP105P1: the ligand-free wild-type (WT-free), 4-phenylimidazole-bound wild-type (WT-4PI), and ligand-free H72A mutant (H72A-free) forms. The BC loop region in the WT-free structure has a unique feature; the side chain of His72 within this region is ligated to the heme iron. On the other hand, this region is highly disordered and widely open in WT-4PI and H72A-free structures, respectively. Histidine ligation of wild-type CYP105P1 was not detectable in solution, and a type II spectral change was clearly observed when 4-phenylimidazole was titrated. The H72A mutant showed spectroscopic characteristics that were almost identical to those of the wild-type protein. In the H72A-free structure, there is a large pocket that is of the same size as the filipin molecule. The highly flexible feature of the BC loop region of CYP105P1 may be required to accept a large hydrophobic substrate.     

Use of intersimple sequence repeats markers to develop strain-specific SCAR markers for Lentinula edodes

Although Lentinula edodes is the second most important cultivated mushroom worldwide, most industrially cultivated strains have been identified only through traditional phenotypic analysis. Here, we report for the first time the use of sequence characterized amplified region (SCAR) markers for strain differentiation. SCAR markers were created by first generating and sequencing single intersimple sequence repeats fragments, and then designing primers based on these sequences to amplify strain-specific fragments of a certain size. One SCAR primer pair, ISL450F/R7 (amplifying a band of c. 450 bp), was designed to identify one strain of L. edodes (strain No. 7). The SCAR primer pair was then used to correctly amplify the single unique fragment from DNA samples taken from a total of 85 strains representing three separate species. Our data provide the foundation for a precise and rapid PCR-based strain-diagnostic system for L. edodes.     

Environmentally friendly microwave ionic liquids synthesis of hybrids from cellulose and AgX (X = Cl,Br)

The purpose of this article was to explore an environmentally friendly strategy to synthesis of biomass-based hybrids. Herein, microwave-assisted ionic liquids method was applied to fabricate the hybrids from cellulose and AgX (X = Cl, Br) using cellulose and AgNO₃. The ionic liquids act simultaneously as a solvent, a microwave absorber, and a reactant. Ionic liquids provided Cl⁻ or Br⁻ to the synthesis of AgCl or AgBr crystals; thus no additional reactant is needed. The products are characterized by X-ray powder diffraction (XRD), Fourier transform infrared spectrometry (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and differential thermal analysis (DTA). The cellulose–Ag/AgCl hybrid and cellulose–Ag/AgBr hybrid were also obtained by using cellulose–AgCl and cellulose–AgBr hybrids as precursors. This environmentally friendly microwave-assisted ionic liquids method is beneficial to the hybrids with high dispersion.     

用ITS和ISSR分子标记技术鉴别香菇生产用种

通过选用香菇生产中存在名称争议或者名称相近或者同一名称但长期在不同地区栽培的12株香菇生产菌株,以及用于种水平对比的豹皮香菇Lentinuslepideus和虎皮香菇Lentinustigrinus的4个菌株,共16个菌株作为供试材料,进行ITS和ISSR遗传分析,并用RAPD技术验证试验结果。结果证明,不同种的ITS长度存在差异,再次证明ITS可以有效区别种之间的菌株;在ISSR的菌株水平分析中,香菇种内材料拥有两个共同的条带,与其他两种菌株的带型图谱有着明显差异,其中5对材料的带型图谱极为相近。RAPD验证结果与上述结果相近。由此可见,结合ITS与ISSR技术是可以用作香菇生产菌株鉴别的,这为ITS和ISSR分子标记技术推广应用于香菇生产菌株的快速准确鉴别提供了技术依据。     

分子诊断技术在乳腺癌检测中的最新进展

乳腺癌是一种严重危害女性健康的恶性肿瘤,对其致病基因的检测有助于肿瘤早期诊断、精准治疗及预后评估.本文总结了近年来乳腺癌相关的热点基因,并对相关基因的分子诊断技术、检测方法及应用进行了综述.首次评述了数字PCR方法用于乳腺癌分子检测的进展.全面对比不同分子诊断技术的差别与优缺点,为乳腺癌关键基因的检测提供指导建议与理论支持,并对未来发展趋势做出展望.