Synthesis and dissociation of soliton molecules in parallel optical-soliton reactors

Mode-locked lasers have been widely used to explore interactions between optical solitons, including bound-soliton states that may be regarded as"photonic molec...     

不同果型和果肉厚度对辣椒耐贮运性的研究

研究了不同果型和果肉厚度辣椒在贮藏运输中的损耗及贮藏期间的营养品质变化,并分析了果型和果肉厚度与辣椒耐贮运性的关系。结果表明:线椒、朝天椒比牛角椒、尖椒耐运输;不同果型辣椒贮藏期间转色率、腐烂率和失水率差异显著,果肉厚度与失水率存在显著性负相关关系;果型比果肉厚度对辣椒贮藏期间维生素C、辣椒素、可溶性糖和可溶性蛋白质等营养成分含量变化的影响明显。      

黑木耳酪氨酸酶的分离纯化与酶学性质研究

本文分离纯化了黑木耳酪氨酸酶,并对酶学性质进行了研究。采用经硫酸铵分级沉淀、Sephadex G-100和DEAE-Sepharose-FF柱层析对粗酶液进行分离纯化,得到电泳纯的黑木耳酪氨酸酶,比活力提高了21.43倍,酶活回收率为27.41%。该酶的酶学性质研究表明:蛋白亚基分子量为12.62ku;最适pH7.0,在中性和碱性条件下稳定;最适温度为40℃,50℃以下温度条件较为稳定;以酪氨酸为底物,米氏常数K m为5.88mmol/L,V max为64.10μmol/min。实验结果表明黑木耳酪氨酸酶具有其它酪氨酸酶相似的酶学特性。      

涂膜处理和酸处理对提高双孢蘑菇储藏稳定性的研究

为了提高双孢蘑菇(Agaricus bisporus)的储藏稳定性,本研究分别采用了三种不同的方法对双孢蘑菇进行处理,它们分别是:酸处理、涂膜处理和酸与涂膜相结合的处理,然后分别测定了储藏过程中的失重率、硬度、色泽变化、多酚氧化酶(PPO)活力和过氧化物酶活力(POD),探讨了不同处理方法对双孢蘑菇储藏稳定性的影响。结果表明:酸与涂膜相结合的处理方式具有最优的效果,它能弥补酸处理和涂膜处理各自的不足之处,既能降低失重率,保持硬度,又能抑制酶活,更好地保持双孢蘑菇的色泽。      

运力限制下区间车与全程车的组合调度模型

针对单条线路双向及单向客流分布的不均衡性, 并考虑实际运营中的运力限制条件, 建立了基于社会总体效益最优为目标、对区间车和双向全程车的发车频率及区间车折返位置同时进行优化的组合调度模型.通过一个算例进行验证, 探讨了在给定运力下组合调度最优发车频率、折返点位置和成本的关系, 并与优化的单一调度进行对比, 结果表明:在客流分布不均衡和运力限制的情况下, 组合调度比单一调度能有效减少系统成本和乘客平均出行时间, 运力限制越强, 组合调度带来的效益更加明显, 运力限制下可以通过组合策略减少系统成本, 且存在系统总成本最低的最佳运力配置.     

Chemistry towards Biology—Instruct: Snapshot

The knowledge of interactions between different molecules is undoubtedly the driving force of all contemporary biomedical and biological sciences. Chemical biology/biological chemistry has become an important multidisciplinary bridge connecting the perspectives of chemistry and biology to the study of small molecules/peptidomimetics and their interactions in biological systems. Advances in structural biology research, in particular linking atomic structure to molecular properties and cellular context, are essential for the sophisticated design of new medicines that exhibit a high degree of druggability and very importantly, druglikeness. The authors of this contribution are outstanding scientists in the field who provided a brief overview of their work, which is arranged from in silico investigation through the characterization of interactions of compounds with biomolecules to bioactive materials.     

Insights into the Structure of the Highly Glycosylated Ffase from Rhodotorula dairenensis Enhance Its Biotechnological Potential

Rhodotorula dairenensis β-fructofuranosidase is a highly glycosylated enzyme with broad substrate specificity that catalyzes the synthesis of 6-kestose and a mixture of the three series of fructooligosaccharides (FOS), fructosylating a variety of carbohydrates and other molecules as alditols. We report here its three-dimensional structure, showing the expected bimodular arrangement and also a unique long elongation at its N-terminus containing extensive O-glycosylation sites that form a peculiar arrangement with a protruding loop within the dimer. This region is not required for activity but could provide a molecular tool to target the dimeric protein to its receptor cellular compartment in the yeast. A truncated inactivated form was used to obtain complexes with fructose, sucrose and raffinose, and a Bis-Tris molecule was trapped, mimicking a putative acceptor substrate. The crystal structure of the complexes reveals the major traits of the active site, with Asn387 controlling the substrate binding mode. Relevant residues were selected for mutagenesis, the variants being biochemically characterized through their hydrolytic and transfructosylating activity. All changes decrease the hydrolytic efficiency against sucrose, proving their key role in the activity. Moreover, some of the generated variants exhibit redesigned transfructosylating specificity, which may be used for biotechnological purposes to produce novel fructosyl-derivatives.     

Conjugates of Methylene Blue with Cycloalkaneindoles as New Multifunctional Agents for Potential Treatment of Neurodegenerative Disease

The development of multi-target-directed ligands (MTDLs) would provide effective therapy of neurodegenerative diseases (ND) with complex and nonclear pathogenesis. A promising method to create such potential drugs is combining neuroactive pharmacophoric groups acting on different biotargets involved in the pathogenesis of ND. We developed a synthetic algorithm for the conjugation of indole derivatives and methylene blue (MB), which are pharmacophoric ligands that act on the key stages of pathogenesis. We synthesized hybrid structures and performed a comprehensive screening for a specific set of biotargets participating in the pathogenesis of ND (i.e., cholinesterases, NMDA receptor, mitochondria, and microtubules assembly). The results of the screening study enabled us to find two lead compounds (4h and 4i) which effectively inhibited cholinesterases and bound to the AChE PAS, possessed antioxidant activity, and stimulated the assembly of microtubules. One of them (4i) exhibited activity as a ligand for the ifenprodil-specific site of the NMDA receptor. In addition, this lead compound was able to bypass the inhibition of complex I and prevent calcium-induced mitochondrial depolarization, suggesting a neuroprotective property that was confirmed using a cellular calcium overload model of neurodegeneration. Thus, these new MB-cycloalkaneindole conjugates constitute a promising class of compounds for the development of multitarget neuroprotective drugs which simultaneously act on several targets, thereby providing cognitive stimulating, neuroprotective, and disease-modifying effects.     

Biofilms and Benign Colonic Diseases

The colon has a very large surface area that is covered by a dense mucus layer. The biomass in the colon includes 500–1000 bacterial species at concentrations of ~10¹² colony-forming units per gram of feces. The intestinal epithelial cells and the commensal bacteria in the colon have a symbiotic relationship that results in nutritional support for the epithelial cells by the bacteria and maintenance of the optimal commensal bacterial population by colonic host defenses. Bacteria can form biofilms in the colon, but the exact frequency is uncertain because routine methods to undertake colonoscopy (i.e., bowel preparation) may dislodge these biofilms. Bacteria in biofilms represent a complex community that includes living and dead bacteria and an extracellular matrix composed of polysaccharides, proteins, DNA, and exogenous debris in the colon. The formation of biofilms occurs in benign colonic diseases, such as inflammatory bowel disease and irritable bowel syndrome. The development of a biofilm might serve as a marker for ongoing colonic inflammation. Alternatively, the development of biofilms could contribute to the pathogenesis of these disorders by providing sanctuaries for pathogenic bacteria and reducing the commensal bacterial population. Therapeutic approaches to patients with benign colonic diseases could include the elimination of biofilms and restoration of normal commensal bacteria populations. However, these studies will be extremely difficult unless investigators can develop noninvasive methods for measuring and identifying biofilms. These methods that might include the measurement of quorum sensing molecules, measurement of bile acids, and identification of bacteria uniquely associated with biofilms in the colon.     

Two Distinct Modes of DNA Binding by an MCM Helicase Enable DNA Translocation

A six-subunit ATPase ring forms the central hub of the replication forks in all domains of life. This ring performs a helicase function to separate the two complementary DNA strands to be replicated and drives the replication machinery along the DNA. Disruption of this helicase/ATPase ring is associated with genetic instability and diseases such as cancer. The helicase/ATPase rings of eukaryotes and archaea consist of six minichromosome maintenance (MCM) proteins. Prior structural studies have shown that MCM rings bind one encircled strand of DNA in a spiral staircase, suggesting that the ring pulls this strand of DNA through its central pore in a hand-over-hand mechanism where the subunit at the bottom of the staircase dissociates from DNA and re-binds DNA one step above the staircase. With high-resolution cryo-EM, we show that the MCM ring of the archaeal organism Saccharolobus solfataricus binds an encircled DNA strand in two different modes with different numbers of subunits engaged to DNA, illustrating a plausible mechanism for the alternating steps of DNA dissociation and re-association that occur during DNA translocation.