复合诱变筛选avermectins高产菌株

由Streptomyces avermitilis初始菌株经过自然分离可以得到三种不同类型的菌株，即灰色粉末型、白色和光秃型。其中灰色粉末型产素水平最高，摇瓶发酵效价达到6835．1μg／ml，B1组分达到56．3％。经过紫外线和亚硝基胍对初始菌株的孢子的诱变及对其原生质体的诱变再生。并且经过异亮氨酸和链霉素的定向筛选，得到的高产菌株摇瓶发酵效价达到8542．9μg／ml，B。组分达到64．9％；同时通过对高产菌株进行传代培养检验其传代稳定性，结果表明，传代3代后，菌株开始退化，并且其发酵效价有比较显著的下降。     

Learning from nature – Novel synthetic biology approaches for biomaterial design

Many biomaterials constructed today are complex chemical structures that incorporate biologically active components derived from nature, but the field can still be said to be in its infancy. The need for materials that bring sophisticated properties of structure, dynamics and function to medical and non-medical applications will only grow. Increasing appreciation of the functionality of biological systems has caused biomaterials researchers to consider nature for design inspiration, and many examples exist of the use of biomolecular motifs. Yet evolution, nature’s only engine for the creation of new designs, has been largely ignored by the biomaterials community. Molecular evolution is an emerging tool that enables one to apply nature’s engineering principles to non-natural situations using variation and selection. The purpose of this review is to highlight the most recent advances in the use of molecular evolution in synthetic biology applications for biomaterial engineering, and to discuss some of the areas in which this approach may be successfully applied in the future.     

Altered patterns of directed connectivity within the reading network of dyslexic children and their relation to reading dysfluency

Reading is a complex cognitive skill subserved by a distributed network of visual and language-related regions. Disruptions of connectivity within this network have been associated with developmental dyslexia but their relation to individual differences in the severity of reading problems remains unclear. Here we investigate whether dysfunctional connectivity scales with the level of reading dysfluency by examining EEG recordings during visual word and false font processing in 9-year-old typically reading children (TR) and two groups of dyslexic children: severely dysfluent (SDD) and moderately dysfluent (MDD) dyslexics. Results indicated weaker occipital to inferior-temporal connectivity for words in both dyslexic groups relative to TRs. Furthermore, SDDs exhibited stronger connectivity from left central to right inferior-temporal and occipital sites for words relative to TRs, and for false fonts relative to both MDDs and TRs. Importantly, reading fluency was positively related with forward and negatively with backward connectivity. Our results suggest disrupted visual processing of words in both dyslexic groups, together with a compensatory recruitment of right posterior brain regions especially in the SDDs during word and false font processing. Functional connectivity in the brain’s reading network may thus depend on the level of reading dysfluency beyond group differences between dyslexic and typical readers.     

日本血吸虫(中国大陆株)表达基因的分离和EST序列测定

目的 运用表达标签技术（ＥＳＴ方法）,从ＳｊｃＤＮＡ文库中分离、鉴定血吸虫表达基因序列。方法 应用ＥＳＴ方法,人ＳｊｃＤＮＡ文库中随机挑出单个重组克陲 ＰＣＲ直接序列分析,通过互联网将获得的ＥＳＴ序列送入ＮＣＢＩＧｅｎＢａｎｋ进行同源性检素,并将发现的未知基因ＥＳＴ序列送入ＮＣＢＩｄｂＥＳＴ以获得ＧｅｎＢａｎｋ进入号。结果 分离了１００个ＳｊＧｅｎＢａｎｋ中已知的血吸虫基因序列,１９个为未知基因序     

丙型肝炎病毒C区的DNA改组

目的：利用DNA改组技术进行不同基因型别丙型肝炎病毒（HCV）基因组C区的人工进化。方法：首先利用PCR扩增了三段具有较高序列同源性的460bp基因片段，然后将其等量混合，在Mg^2＋存在的条件下，用脱氧核糖核酸酶（DNase Ⅰ）切割成50bp左右的小片段。这些小片段在不外加引物的条件下，利用PCR反应进行重聚，再将重聚物经过一轮正常的PCR扩增。结果：获得了与原片段大小相当的基因片段。结论：这一技术为进一步筛选高活性的HCVC区基因打下基础，有利于从一组序列同源性程度较高的基因库构建随机嵌合基因，并为改组其他基因家族提供了借鉴。     

Directed evolution towards protease-resistant hirudin variants

Hirudin, a thrombin-specific inhibitor, is efficiently digested and inactivated by proteases with pepsin- and chymotrypsin-like specificity. Using a combination of phage display selection and high-throughput screening methods, several variants of recombinant hirudin were generated. Only very few variants comprising amino acid substitutions in the amino-terminal domain (residues 1-5) and in the carboxyl-terminal tail (residues 49, 50, and/or 56, 57, 62-64) were identified that showed thrombin inhibition activities similar to those of the wild-type polypeptide. Analysis of protease susceptibility, however, revealed that mutations, which conferred protease resistance, simultaneously diminish thrombin inhibition activity. This is particularly apparent for substitutions in the region of residues 56-64, which forms a large number of electrostatic and hydrophobic interactions with thrombin in the crystal structure of the complex. Unlike wild-type hirudin, the variant comprising Pro(50)- ...-His(56)-Asp(57)- ...-Pro(62)-Pro(63)-His(64) is completely resistant to pepsin and chymotrypsin cleavage; however, this is at the expense of thrombin inhibition activity where there is a 100-fold increase in the IC50 value. The frequent replacement of wild-type amino acids by proline at major protease cleavage sites indicates that at least pepsin- and chymotrypsin-like enzymes may exhibit a (conformational) specificity concerning the P1 and P2 positions. On the basis of these results, proline substitutions appear to be a general strategy to design polypeptides that are not susceptible to digestion by a broader range of different proteases.     

Directed attention alters the temporal activation patterns of back extensors during trunk flexion–extension in individuals with chronic low back pain

In chronic low back pain patients (CLBP), neuromuscular and pain intensity have been identified as contributing factors in the disability of the individual. However, it is unclear whether pain intensity influences neuromuscular activation and if directed attention mediates this relationship. Thus, the purpose of this study was to determine the effect of directed attention in individuals with different pain intensities on back extensor activation profiles. Fifty-four CLBP patients were separated into either high- or low-pain groups. Surface electromyograms were recorded from back muscles while the subjects performed a trunk flexion motion for four different attention conditions. Pattern recognition and repeated measures ANOVAs were used to examine the effect of sex, attention and pain intensity on temporal muscle activation patterns. The results showed that there was a significant sex × attention × pain interaction. The largest changes in muscle timing were observed in the low-pain group when their attention was focused on their pain, but the pattern of muscle activation differed between sexes. For males, a rapid decline in activation at mid-extension occurred, whereas females showed delayed activation at the beginning of extension. Overall, this study demonstrated that directed attention on pain had an effect on trunk muscle temporal recruitment, and that this relationship differed between sexes and pain groups. This suggests that sex-specific mechanisms may alter the neuromuscular control of the spine in CLBP patients for different pain levels.