可视化分析四肽构象空间中的模式

用一种可视的方式分析四肽构象空间中的聚集情况,从而直观地建立了四肽结构类和二级结构之间的联系.据此给出了四肽构象类的一种划分方案,并将此方案应用于更长肽段构象模式的发现和评估其他方法对肽段构象分类的合理性.实验结果与其他方法相比更具有可解释性.     

R~(49)A~(50)RGDN~(54)P~(55)突变成I~(49)P~(50)RGDM~(54)P~(55)对华丽蛇毒素活性的影响(英文)

用基因点突变技术将已知具有强抑制血小板凝集作用的去整合蛋白———kistrin的RGD袢区IPRGDMP替换抑制血小板凝集作用较弱的elegantinRGD袢相应部位的RARGDNP,重构一个新的杂合的去整合蛋白,然后,分析该杂合蛋白对血小板凝集的抑制作用。结果表明,重组的杂合去整合蛋白比野生型elegantin具有更强的抑制血小板凝集活性。推测RGD顺序两翼的氨基酸残基在保持去整合蛋白的结构和功能中起重要作用。     

建安动荡的政局与诗歌主题的嬗变

建安时代是一个割据动荡的时代,同时,建安时代也是文学自觉的时代。动乱的政局对建安文学尤其是诗歌产生了深远的影响。政治局势直接影响到诗歌主题的变化,使建安诗歌主题较汉代诗歌主题呈现出了新的面貌。     

A Simple Structure for Signal Amplification

It has been found that a triple-node feed-forward motif has a function of signal amplification, where two input nodes receive the external weak signal and jointly modulate the response of the third output node [Liang et al.,Phys. Rev. E 88(2013) 012910]. We here show that the signal amplification can be further enhanced by adding a link between the two input nodes in the feed-forward motif. We further reveal that the coupling strength of the link regulates the enhancement of signal amplification in the modified feed-forward motif. We finally analyze the mechanism of signal amplification of such simple structure.     

Progress in 50 years of viroid research—Molecular structure,pathogenicity, and host adaptation

Viroids are non-encapsidated, single-stranded, circular RNAs consisting of 246–434 nucleotides. Despite their non-protein-encoding RNA nature, viroids replicate autonomously in host cells. To date, more than 25 diseases in more than 15 crops, including vegetables, fruit trees, and flowers, have been reported. Some are pathogenic but others replicate without eliciting disease. Viroids were shown to have one of the fundamental attributes of life to adapt to environments according to Darwinian selection, and they are likely to be living fossils that have survived from the pre-cellular RNA world. In 50 years of research since their discovery, it was revealed that viroids invade host cells, replicate in nuclei or chloroplasts, and undergo nucleotide mutation in the process of adapting to new host environments. It was also demonstrated that structural motifs in viroid RNAs exert different levels of pathogenicity by interacting with various host factors. Despite their small size, the molecular mechanism of viroid pathogenicity turned out to be more complex than first thought.     

禾谷炭疽菌内吞相关蛋白找寻及其生物信息学

真菌通过内吞的质膜变形运动将细胞以外的物质转运到细胞内,有关植物病原丝状真菌中内吞作用相关蛋白及其特征研究尚不多见,对其发挥内吞作用的NPFxD相关蛋白尚未见报道.运用内吞作用关键词在NCBI数据库中搜索,同时,以模式生物构巢曲霉中NPFxD蛋白序列为基础,通过Blastp开展在线比对分析,明确禾谷炭疽菌中具有NPFxD基序的蛋白有6个,根据同源关系分别命名为CgTPO1、CgMYO2、CgCRN3、CgNPF4、CgGBP5和CgTRM6;并从跨膜、保守结构域、亚细胞定位、理化性质以及信号肽、二级结构等方面对上述蛋白开展生物信息学分析.结果表明,不同跨膜预测软件结果并不相同,保守结构域种类较多且缺少同一类结构域,蛋白亚细胞定位位置多样且不尽相同,尤以G、A氨基酸残基所占比例最高,仅CgNPF4具有明显的信号肽,而CgMYO2蛋白具有比例相对高的α螺旋结构.此外,通过遗传关系分析明确了禾谷炭疽菌中NPFxD蛋白和炭疽菌属病菌具有较高的同源性和较近的亲缘关系,为深入探索NPFxD基序蛋白在炭疽病中的功能奠定了坚实的理论基础.     

A cooperative fast annealing coevolutionary algorithm for protein motif extraction

By integrating the cooperative approach with the fast annealing coevolutionary algorithm (FAEA), a so-called cooperative fast annealing coevolutionary algorithm (CFACA) is presented in this paper for the purpose of solving high-dimensional problems. After the partition of the search space in CFACA, each smaller one is then searched by a separate FAEA. The fitness function is evaluated by combining sub-solutions found by each of the FAEAs. It demonstrates that the CFACA outperforms the FAEA in the domain of function optimization, especially in terms of convergence rate. The current algorithm is also applied to a real optimization problem of protein motif extraction. And a satisfactory result has been obtained with the accuracy of prediction achieving 67.0%, which is in agreement with the result in the PROSITE database.     

Diagnostic assessment of preparedness of level one sports science students for biomechanics modules

The primary objective of this study was to investigate the use of a diagnostic test to assess the prepardness of level one students for a sports biomechanics module. During their first week at university, a cohort of 108 students completed a diagnostic test at the end of their first lecture in sports biomechanics, with no prior notice. Upon completion of the 12-week module, the students sat the same diagnostic test, again with no prior notice. The results from the initial test were used to identify areas that required emphasis and additional resources during delivery of the module. The comparison of test results from the two sittings was used as a measure of the level of success of the module in increasing the level of student understanding. It is concluded that the design of a diagnostic test specific to a module can be used both to inform subsequent teaching and to assess success of teaching methods.     

Supramolecular interactions in some organic hydrated 2,4,6-triaminopyrimidinium carboxylate and sulfate salts

Four salts, namely, 2,4,6-triaminopyrimidinium 6-chloronicotinate dihydrate, C₄H₈N₅⁺·C₆H₃ClNO₂⁻·2H₂O, (I), 2,4,6-triaminopyrimidinediium pyridine-2,6-dicarboxylate dihydrate, C₄H₉N₅²⁺·C₇H₃NO₄²⁻·2H₂O, (II), 2,4,6-triaminopyrimidinediium sulfate monohydrate, C₄H₉N₅²⁺·SO₄²⁻·H₂O, (III), and 2,4,6-triaminopyrimidinium 3,5-dinitrobenzoate dihydrate, C₄H₈N₅⁺·C₇H₃N₂O₆⁻·2H₂O, (IV), were synthesized and characterized by X-ray diffraction techniques. Proton transfer from the corresponding acid to the pyrimidine base has occurred in all four crystal structures. Of the four salts, two [(I) and (IV)] exist as monoprotonated bases and two [(II) and (III)] exist as diprotonated bases. In all four crystal structures, the acid interacts with the pyrimidine base through N—H…O hydrogen bonds, generating an R₂²(8) ring motif. The sulfate group mimics the role of the carboxylate anions. The water molecules present in compounds (I)–(IV) form water-mediated large ring motifs. The formation of water-mediated interactions in these crystal structures can be used as a model in the study of the hydration of nucleobases. Water molecules play an important role in building supramolecular structures. In addition to these strong hydrogen-bonding interactions, some of the crystal structures are further enriched by aromatic π–π stacking interactions [(I) and (II)].     

Ambidextrous α,γ‐Hybrid Peptide Foldamers

Molecular chirality is ubiquitous in nature. The natural biopolymers, proteins and DNA, preferred a right‐handed helical bias due to the inherent stereochemistry of the monomer building blocks. Here, we are reporting a rare co‐existence of left‐ and right‐handed helical conformations and helix‐terminating property at the C‐terminus within a single molecule of α,γ‐hybrid peptide foldamers composed of achiral Aib (α‐aminoisobutyric acid) and 3,3‐dimethyl‐substituted γ‐amino acid (Adb; 4‐amino‐3,3‐dimethylbutanoic acid). At the molecular level, the left‐ and right‐handed helical screw sense of α,γ‐hybrid peptides are representing a macroscopic tendril perversion. The pronounced helix‐terminating behaviour of C‐terminal Adb residues was further explored to design helix–Schellman loop mimetics and to study their conformations in solution and single crystals. The stereochemical constraints of dialkyl substitutions on γ‐amino acids showed a marked impact on the folding behaviour of α,γ‐hybrid peptides.