Structure-directing Effect on Synthesis of Layered Aluminophosphates with Same Topology
DNA的复制课件-2023-2024学年高一下学期生物人教版(2019)必修2
C.这M个子代T₂噬菌体中，含32P的T₂噬菌体所占的比例为1/M
有2个，故其所占的比例为2/M,C 错误。培养足够长的时间，会出现 不含32P而含35S的T₂噬菌体，但一般不会出现含32P的大肠杆菌，D 错 误。
3 、在一个密闭的容器里，用含有同位素13C的脱氧核苷酸合成一个 DNA分子，然后加入普通的含12C的脱氧核苷酸，经n次复制后，所得DNA 分子中含¹2C的脱氧核苷酸链数与含13C的脱氧核苷酸链数之比是
特点 半保留复制；边解旋边复制；多起点复制；双向复制
结果 子链与母链结合，构成两个相同的新的DNA分子
意义 保持了遗传信息的连续性
总结规律
规律1:若 一 个DNA 复制n次。
1.在子代中共形成 2n 个DNA, 其中含有亲代
DNA链的DNA分子数 2 0 2.含有亲代DNA链的DNA分子数占DNA分子总
D . 含 1 0 0 个 碱 基 对 ( 其 中 胞 嘧 啶 6 0 个 ) 的 DNA复 制 3 次 共 需 要 2 8 0 个
2、用 DNA双链均被32P标记的一个T,噬菌体侵染被35S标记的大肠杆菌， 一段时间后释放出出了M个子代T₂噬菌体。下列有关叙述正确的是
()
A.用32P标记T₂噬菌体的方法与用35S标记大肠杆菌的方法相同
It has not eseaped our notice that the specife pairing we have postulated immediately guggests a p⁰ssible copying mechanism for the genetic materiaI.
Full details of the structure,including the conditions assumed in building it,together with a set of co-ordinatos for the atoms,will be published elsewhere.
heterogeneous interfacial structure
heterogeneous interfacial structure英文版Heterogeneous Interfacial StructureHeterogeneous interfacial structure refers to the structural differences that exist at the boundary between two different materials or phases. This structure plays a crucial role in determining the physical and chemical properties of the interface, as well as its stability and reactivity.At the interface between two materials, the atomic arrangement, bonding configuration, and electronic structure can all differ significantly from the bulk materials on either side. This heterogeneity can lead to a range of unique properties, such as charge accumulation, bond formation, and catalytic activity. For example, in the field of materials science, heterogeneous interfaces are often exploited to enhance the performance of devices such as solar cells and fuel cells.The study of heterogeneous interfacial structure is challenging due to the complexity of the interactions involved. Experimental techniques such as scanning probe microscopy, spectroscopy, and diffraction methods can provide insights into the atomic-scale structure and electronic properties of interfaces. Computational modeling is also an important tool for understanding and predicting interfacial behavior.In recent years, there has been increasing interest in the use of heterogeneous interfacial structures in nanotechnology and materials science. This interest is driven by the potential for novel materials with enhanced properties, as well as the development of new technologies such as nanodevices and sensors.In conclusion, heterogeneous interfacial structure is a crucial aspect of materials science and nanotechnology. Its understanding and control offer the potential for the development of novel materials and devices with enhanced performance and functionality.中文版异质界面结构异质界面结构指的是两种不同材料或相之间的边界处存在的结构差异。
第二语言习得概论-考研复习
★1. SLA (Second language acquisition) is the process by which a language other than the mother tongue is learnt in a natural setting o r i n a c l a s s r o o m. ★2. Acquisition vs. Learning (Krashen1982)Acquisition refers to the learning of a language unconsciously under natural settings where learners pay attention only to the meanings or contents rather than forms or grammars.Learning refers to the learning of a language consciously under educational settings where learners mainly pay attention to forms or grammars.3. Factors affecting SLASocial factors (external factors)Learner factors (internal factors)Social factors (external factors)Social contextLanguage policy and the attitude of the public sector;Social demandWith the trend of globalization of the world economy , it is widely accepted among educators and national leaders that proficiency in another language is an indispensable quality of educated people Learner factors (internal factors)Motivation ，Age ，Learning strategy4.Behaviorist learning theoryBehaviorist learning theory is a general theory of learning (i.e. it applies to all kinds of learning, not just language learning).It views learning as the formation of habits. The association of a particular response with a particular stimulus constituted a habit. It is formed when a particular stimulus became regularly linked with a particular response.When applied to SLA, the process of second language acquisition is regarded as a process of habit formation.5. The causes of errors according to behaviorismDifferences between the first and second language create learning difficulty which results in errors.Behaviorist learning theory predicts that transfer will take place from the first to the second language.Transfer will be negative when there is proactive inhibition. In this case errors will result. Errors, according to behaviorist theory, were the result ofnon-learning, rather than wrong learning.The means used to predict potential errors by behaviorists is Contrastive Analysis.6. StructuralismLanguage was viewed as a coded system consisting of structurally related elements (phonemes, morphemes, words, structures and sentence patterns)7. What is contrastive analysis (CA)?Contrastive analysis is an inductive investigative approach based on the distinctive elements in a language. It involves the comparison of two or more languages or subsystems of languages in order to determine both the differences and similarities between them. It could also be done within one language. Contrastive analysis can be both theoretical and applied according to varied purposes.8. Contrastive Analysis Hypothesis (CAH)Contrastive analysis is a way of comparing languages in order to determine potential errors for the ultimate purpose of isolating what needs to be learned and what does not need to be learned in an L2 situation.According to CAH, L2 errors are result of differences between the learner’s first language and the target language. The strong form of the hypothesis claims that these differences can be used to predictall errors that will occur. The weak form of the hypothesis claims that these differences can be used to identify some out of the total errors that actually arise.9.difference vs difficulty“Difference” is a linguistic concept, whereas “difficulty” is a psychological concept. Therefore, the level of learning difficulty cannot be inferred directly from the degree of difference between two language systems.10. Definition of Error analysis (EA)the study and analysis of the errors made by second and foreign language learners (Longman Dictionary of Applied Linguistics, p.96). It involves collecting samples of learner language, identifying the errors in these samples, describing these errors, classifying them according to their hypothesized causes, and evaluating theirs seriousness.11.Interlingual error: deviated forms resulting from the interference of one’s L1, or the negative transfer of one’s mother tongue.Intralingual error: ①deviated forms in learner language that reflect learners’ transitional competence and which are the results of such learning process as overgeneralization.②confusion of L2 rules12. Factors causing errors1. Language transfer2. Overgeneralization3. Learner differences3. Strategies in L2 learning5. Strategies of L2 communicatione.g. The two students changed eyes and eyebrows in class.13. Types of learner strategyLearning strategy, Production strategy 表达策略Communication strategy:Communication strategies are employed when learners are faced with the task of communicating meanings for which they lack the requisite linguistic knowledge. Typical communication strategies are paraphrase and mime.14. Classifications of learning strategy(Cohen 2006)(2) By function: Metacognitive; Cognitive; Socio-affective(3) By skill: listening, speaking, reading, writing, vocabulary, or translation strategies.15. Meta-cognitive strategiesMeta-cognitive strategy is the planning for learning, thinking about the learning process, monitoring of one’s production or comprehension, and evaluating learning after an activity iscompleted.16. Cognitive strategiesCognitive strategies refer to the steps or operations used in learningor problem-solving that require direct analysis, transformation, or synthesis of learning material.Repetition, Resourcing, Directed physical response, Translation, Grouping, Note-taking , Deduction Recombination, Imagery, Auditory representation, Key word, Contextualization, Elaboration, Transfer, Inferencing17. Individual learner variablesPersonal factors:group dynamics; attitudes to the teacher and course materials; learning techniquesGeneral factors:age; aptitude; cognitive style; motivation; personality18. MotivationIntegrative motivation 融合型动机is present in learners who identifywith the target culture, would like to resemble members of the target culture and who would like to participate in the target culture. Itis assumed to be based in the personality of the learner.Instrumental orientation工具型动机refers to those cases where the learners are interested in learning the language for the possiblebenefits, that is, the learner’s goal is functional.Resultative motivation:因果性动机 Learners’motivation is strongly affected by their achievement.Intrinsic motivation:内在兴趣动机Motivation as intrinsic interest. Motivation as a multi-componential construct:Motivation = effort + desire to achieve goal + attitudesTask motivation: the interest felt by the learner in performing different learning tasks.★19. Definition –interlanguageInterlanguage is the approximate language system that the learner constructs for use in communication through the target language. (Larry Selinker)It is independent of both the learner’s first language and the target language.It suggests that learners’ language is between L1 AND L2 and that it is a continuum along which all learners traverse.★20.Definition of fossilizationFossilization refers to the state in which the second language learners stop to learning when their internalized rule system contains rules different from the target language. That is to say, the interlanguage stops evolving towards the TL.21. Classification of fossilizationTemporary fossilization: the phenomenon is alterable under certain conditions.Permanent fossilizationThis means the learne r’s language stops evolving for ever. Because stable stage is not real fossilization, so there is no real permanent fossilization.22. Causes of fossilizationInternal: Motivation; Communicative needs; Acquisition deviceExternal: Communicative pressureLack of learning opportunitiesFeedback:positive cognitive feedbacks cause fossilization ;(e.g. “Oh,I see”)negative feedbacks help to prevent fossilization.(e.g. “I don’t understand you” )★23. Definition of UGCook(1985) summarizing the Chomskyan position, defines ‘universal grammar’ as ‘the properties inherent in the human mind’. Universal grammar consists of a set of general principles that apply to all language rather than a set of particular rules.24. MarkednessMarkedness refers to the idea that some linguistic structures are ‘special’ or ‘less natural’ or ‘less basic’ than others.Linguists working in the Chomskyan school suggest that linguistic rules can either be part of the core grammar (i.e. the universal rules) or be part of the periphery.Core rules are considered to be unmarked and therefore easily acquired.Periphery roles are considered to be and therefore different to learn.25.Krashen’s Monitor ModelKrashen’s monitor model mainly consists of the following five hypothses:(1) Acquisition-Learning Hypothesis:there are two kinds of ways of learning a second language ,i.e., acquisition and learning.(2) Natural Order Hypothesis:SLA follows a universal route that is not influenced by factors such as the learners’ first language, age, and the context (classroom or natural setting).Implications:Errors are developmental and are a natural byproduct of learning –tolerate them.Allow learners to make errors and do not correct them(3) The Input Hypothesis cIt laims a move along the developmental continuum by receiving comprehensible input.We acquire, only when we understand the structure that is “a little beyond” where we are nowComprehensible input is defined as L2 input just beyond the Learner’s current L2 competence, in terms of its syntactic complexity. If a learner’s current competence is i then comprehensible input is i+1. Input which is either too simple (i) or too complex (i+2/3/4…) will not be useful for acquisition.(4) The affective filter hypothesisSLA is affected by factors like Motivation, Self-confidence, Anxiety and so on.Learners who suffer from anxiety or lack of motivation or negative attitude somehow switch off their comprehension mechanisms and so even if they are provided comprehensible input, they will not be able to process the input. Therefore a low affective filter is important.(5) Monitor hypothesisBoth language learners and native speakers typically try to correct any errors in what they have just said. This is referred to as monitoring.Krashen uses the term Monitoring (with a big M) to refer to the way the learner used learnt knowledge to improve utterances producedby means of acquired knowledge.26. language transferLanguage transfer is the influence resulting from the similarities and differences between the target language and any other language that has been previously( and perhaps imperfectly ) acquired. ★27. LAD (language acquisition device)The LAD is a system of principles that children are born with that helps them learn language, and accounts for the order in which children learn structures, and the mistakes they make as they learn.★28. critical age period hypothesisIt claims that there a period when language acquisition can take place naturally and effortlessly, but after a certain age the brain is no longer able to process language input in this. Researchers differ over when the critical period comes to an end.★29. field independent vs. field independentLearners are different in the ways of receiving, conceptualizing, organizing, and recalling information.Field dependents operate holistically (i.e. they see the field as a whole),Whereas field independents operate analytically (i.e. they see the field in terms of its component parts).★30. input vs. intakeInput refers to the language learners are exposed to.It serves as the data which learners must use to determine the rules of the target language.However, not all available input is processed by the learner, either because some of it is not understood or because some of it is not attended to.That part of input that is processed, assimilated and fed into the interlanguage system is referred to as intake.★31.attitudes vs. aptitude vs. intelligenceAttitudes refer to the learner’s beliefs about factors such as the target language culture, their own culture, their teacher and the learning tasks they are given.Aptitude refers to the specific ability a learner has for learning a second language.Intelligence refers to the general ability to master academic skills.32. competence vs. performanceWhen learners acquire a L2, they internalize rules which are then organized into a system. This constitutes their competence.The actual use of this system to comprehend and produce utterances is referred to as performance.33. OvergeneralizationIt refers to the extension of some general rule to items not covered by this rule in the target language.34. foreigner talk vs. teacher talkWhen native speakers address learners, they make adjustments in both language form and language function to facilitate understanding. These adjustments are referred to as foreigner talk.When teachers address learners, they make adjustments in both language form and language function to facilitate understanding. These adjustments are referred to as foreigner talk.35. formulaic speech vs. patternsFormulaic speech consists of expressions which are learned as unanalysable wholes and employed in particular occasions.Patterns are one type of formulaic speech. They are unanalysable units which have one or more open slots, e.g. ‘Can I have a —’。
空间位阻效应英语
空间位阻效应英语The Steric Hindrance Effect in SpaceThe concept of steric hindrance, also known as steric inhibition or steric crowding, is a fundamental principle in organic chemistry and has significant implications in the field of space exploration. This phenomenon occurs when the spatial arrangement of atoms or molecules within a chemical structure impedes or restricts the desired reaction or interaction, often due to the bulkiness or size of the substituents involved.In the context of space exploration, the steric hindrance effect plays a crucial role in the design and development of various spacecraft components, materials, and systems. The unique challenges posed by the harsh environment of space, such as extreme temperatures, radiation, and the absence of gravity, require a deep understanding of how steric effects can influence the performance and stability of these systems.One of the primary areas where steric hindrance becomes a significant consideration is in the selection and engineering of spacecraft materials. The materials used in spacecraft constructionmust be able to withstand the rigors of launch, the vacuum of space, and the various stresses encountered during mission operations. The spatial arrangement of atoms and molecules within these materials can greatly impact their mechanical properties, thermal stability, and resistance to degradation.For instance, the choice of polymers used in spacecraft insulation or structural components must take into account the steric effects that can influence their thermal expansion, flexibility, and resistance to radiation damage. The selection of lubricants and sealants for moving parts, such as hinges or joints, must also consider the steric hindrance that could affect their performance and longevity in the space environment.Another crucial application of the steric hindrance effect in space exploration is the design of spacecraft propulsion systems. The efficient and reliable operation of rocket engines, ion thrusters, or other propulsion technologies often depends on the careful management of the spatial arrangement of reactants, catalysts, or propellants within the system. Steric effects can influence the kinetics of chemical reactions, the flow dynamics of propellants, and the overall efficiency of the propulsion system.Furthermore, the steric hindrance effect plays a significant role in the development of space-based sensors and instrumentation. Thedesign of optical systems, such as telescopes or spectrometers, must account for the spatial constraints imposed by the instrument's components, including lenses, mirrors, and detectors. The arrangement of these elements can impact the system's resolution, sensitivity, and overall performance.In the field of astrochemistry, the steric hindrance effect is also relevant in the study of complex organic molecules and their formation in the interstellar medium. The spatial arrangement of atoms within these molecules can influence their stability, reactivity, and the pathways by which they are synthesized in the harsh conditions of space.To address the challenges posed by steric hindrance in space exploration, researchers and engineers employ various strategies, such as molecular modelling, computational chemistry, and advanced materials science. These tools help them to predict, analyze, and mitigate the effects of steric crowding, enabling the development of more robust and efficient spacecraft systems.In conclusion, the steric hindrance effect is a critical consideration in the design and development of spacecraft, systems, and materials for space exploration. By understanding and leveraging this fundamental principle of organic chemistry, scientists and engineers can create innovative solutions that push the boundaries of what ispossible in the exploration and utilization of the final frontier – the vast expanse of space.。
Astructurefordeoxyribosenucleicacid
Complexity: The sequence of bases on one strand of DNA determines the sequence on the potential strand through the principle of completeness This means that the order of bases on one strand is complete to the order on the other strand, with A pairing with T and G pairing with C
Structural constraint elements
The structural constraint elements of DNA include the nucleotides, which are made up of a phase group, a deoxyribose sugar, and a nitrogen base (A, T, G, or C)
In addition to the nucleotides, DNA also contains epigenetic marks such as methylation and acetylation, which can affect gene expression without altering the DNA sequence itself
Characterisation-and-immunomodulating-activities-of-exo-polysaccharides-from-submerged-cultivation
Characterisation and immunomodulating activities of exo-polysaccharides from submerged cultivation of HypsizigusmarmoreusBing-Zhao Zhang a ,b ,e ,Kari T.Inngjerdingen b ,Yuan-Feng Zou b ,Frode Rise c ,Terje E.Michaelsen b ,d ,Pei-Sheng Yan a ,⇑,Berit S.Paulsen baSchool of Marine Science and Technology,Harbin Institute of Technology,Weihai Campus,264209Weihai,ChinabDepartment of Pharmaceutical Chemistry,School of Pharmacy,University of Oslo,P.O.Box 1068,Blindern,0316Oslo,Norway cDepartment of Chemistry,University of Oslo,P.O.Box 1033,Blindern,0315Oslo,Norway dDepartment of Bacteriology and Immunology,Norwegian Institute of Public Health,P.O.Box 4404,Nydalen,0403Oslo,Norway eGuangzhou Institute of Advanced Technology,Chinese Academy of Sciences,511458Nansha,Guangzhou,Chinaa r t i c l e i n f o Article history:Received 13January 2014Received in revised form 16March 2014Accepted 24April 2014Available online 4May 2014Keywords:Hypsizigus marmoreus PolysaccharidesComplement fixating Macrophage stimulating Molecular structuresa b s t r a c tExo-polysaccharides were purified and characterized from the fermentation broth of Hypsizigus marmoreus ,a popular edible mushroom consumed in Asia.Among them,B-I-I and B-II-I exhibited potent complement fixating activity,meanwhile,B-N-I,B-I-I,B-II-I and B-II-II exhibited significant macrophage stimulating activity.Molecular weights of the four exo-polysaccharides were determined to be 6.3,120,150and 11kDa respectively.Molecular characterisation showed that B-N-I is basically an a -1?4glu-can,with branches on C 6;B-I-I is a heavily branched a -mannan with 1?2linked main chain.B-II-I and B-II-II,have a backbone of rhamno-galacturonan with 1?2linked L -rhamnose interspersed with 1?4linked galacturonic acid.Structure–activity relationship analysis indicated that monosaccharide compositions,molecular weight,certain structural units (rhamno-galacturonan type I and arabinogalac-tan type II)are the principal factors responsible for potent complement fixating and macrophage-stimu-lating activities.Their immunomodulating activities may,at least partly,explain the health benefits of the mushroom.Ó2014Elsevier Ltd.All rights reserved.1.IntroductionMedicinal mushrooms (Basidiomycetes)have attracted more and more scientific attention in the past decades,due to their health promoting benefits and medical efficacy.They comprise a vast source of pharmaceutical products with potential antitumour and immunomodulating properties (Smith,Rowan,&Sullivan,2002).The complement system is an important part of the innate immune system and also interacts and coordinates adaptive immune responses.Activation of complement leads to proteolytic cascade reactions,terminating in opsonophagocytosis,or lysis,of pathogens as well as the generation of an inflammatory response through the production of potent proinflammatory chemokinesand cytokines (Dunkelberger &Song,2010).The interaction between the complement system and polysaccharides could be employed as an alternative therapeutic strategy to treat inflamma-tory diseases (Yamada &Kiyohara,1999).As an indicator for immune modulating effects,complement fixating activities of polysaccharides from several plants have been reported (Diallo,Paulsen,Lijeback,&Michaelsen,2003;Inngjerdingen,Coulibaly,Diallo,Michaelsen,&Paulsen,2006).Macrophages play important roles in both the innate and adaptive immune systems (Phillip,Christina,&Lesley,2005).A hallmark of macrophage activation is release of cytokines and nitric oxide (NO)(MacMicking,Xie,&Nathan,1997).Polysaccharides isolated from mushrooms have been reported to exert antitumour activities through activation of the immune response of the host organism.Acidic polysaccharides isolated from Phellinus linteus ,enhance the antitumour activity of perito-neal macrophages through the up-regulation of nitric oxide and tumour necrosis factor-a (Kim,Choi,Lee,&Park,2004).The neutral polysaccharide fractions isolated from Agaricus bisporus white/10.1016/j.foodchem.2014.04.0920308-8146/Ó2014Elsevier Ltd.All rights reserved.⇑Corresponding author.Address:School of Marine Science and Technology,Harbin Institute of Technology,West Culture Road 2,264209Weihai,China.Tel./fax:+866315687230.E-mail address:psyan6@ (P.-S.Yan).button mushroom,mainly consisting of mannose,glucose,fructose and xylose,exhibited antitumour activities through macrophage stimulation(Jeong,Koyyalamudi,Jeong,Song,&Pang,2012).Hypsizigus marmoreus is an edible mushroom successfully culti-vated and commercially available in Asia.The mushroom has become increasingly popular in China,South Korea and Japan due to its mildly sweet nuttyflavour and crunchy texture,and probably because of the existence of some medicinal beneficial components.HM23,a novel collagen-binding protein,isolated from the fruiting bodies of H.marmoreus,was reported to inhibit the Lewis lung carcinoma cell adhesion to type IV collagen (Tsuchida,Aoyagi,Odani,Mita,&Isemura,1995).A novel thermo-stable ribosome-inactivating protein with antifungal and antiproliferative activities,hypsin,was separated from the fruiting bodies of H.marmoreus by Lam and Ng(2001).Another ribosome inactivating protein showing antiproliferative activity,marmorin, was isolated from fresh fruiting bodies of H.marmoreus and veri-fied to possess HIV-1reverse transcriptase inhibitory activity (Wong,Wang,&Ng,2008).Hypsiziprenol A9,which is also isolated from methanol extract of H.marmoreus,was reported to inhibit the growth of HepG2cells by inducing G1phase cell cycle arrest due to the inhibition of expression of phosphorylated retinoblastoma pro-tein(ppRb),cyclin D1and cyclin E(Chang et al.,2004).Further-more,various extracts of H.marmoreus fruiting bodies have been investigated and reported to exhibit several other kinds of biolog-ical activities,such as antitubercular(Akihisa et al.,2005),and anti-allergic(Yoshino et al.,2008).Nevertheless,the exo-polysaccharides from cultivation broth of H.marmoreus have not been thoroughly investigated although sub-merged cultivation is widely used in the production of polysaccha-rides from medicinal mushrooms(Wang,Shi,Zhu,Yang,&Du, 2009).Our previous study has shown that the exo-polysaccharides from fermentation broth of H.marmoreus possess potent inhibitory activity against a human gastric cancer cell line(SGC-7901)in vitro (Zhang,Yan,Chen,&He,2012).The aim of the present study was to investigate the purification procedure,immunomodulating activi-ties,structural elucidation,and structure–activity relationships of the exo-polysaccharides obtained from H.marmoreus.2.Materials and methods2.1.Fungi strains and submerged cultivationThe fungus H.marmoreus JB06was screened and preserved in the Applied and Marine Microbiology Lab at Harbin Institute of Technology,Weihai campus,Weihai,China.It was cultivated according to our previous description(Zhang et al.,2012).The mushroom was initially cultivated on PDA medium(fresh potato 20%,glucose2%and agar1.5%)in a Petri dish at25°C for10days. Ten agar plugs,10mm in diameter with young mycelia were punched out by a puncher from the marginal culture and inoculated into250ml Erlenmeyerflasks containing100ml of seed culture medium including3.5%of glucose,11%of potato,1.75%of yeast extract,0.1%of K2HPO4and0.05%of MgSO4,and then culti-vated on a rotary shaker at150rpm,25°C for9days.The fermen-tation experiments were performed in500mlflasks containing 300ml of fermentation culture medium including soya peptone 2.5%,glucose2.346%,sweet potatoes powder1.0%,corn powder 0.688%,flour 1.0%,soy powder 1.0%,CaCO30.088%,K2HPO4 0.172%,pH7.0and was inoculated with15%(v/v)of the seed medium culture on above rotary shaker at25°C for8days.After cultivation the supernatant and mycelia in the fermentation broth were separated with centrifugation at4500rpm for20min at room temperature.Totally,1.36L of supernatant were collected and pooled from5batches of cultivation.The pigments and proteins in the supernatant were removed by macroporous resins (The Chemical Plant of Nan Kai University,Tianjin,China).Fourfold volumes of ethanol(95%)were added to the supernatant and the crude exo-polysaccharide was obtained after precipitation and lyophilization.2.2.Isolation and purification of the exo-polysaccharides2.2.1.Isolation of exo-polysaccharides by anion exchange chromatographyThe crude exo-polysaccharide was dissolved in distiled water;a water bath(100°C)was used for dissolution.The soluble part was filtered through a0.45l mfilter(Millipore,USA)and applied to an XK50anion exchange column(GE Healthcare,USA)packed with ANX Sepharose™4Fast Flow.The neutral fraction wasfirst eluted with distiled water,and then acidic fractions were obtained after elution of the column with a linear NaCl gradient(0–1.5M)in water.Fractions of10ml were collected with a Pharmacia LKB SuperFrac fraction collector.The carbohydrate content in the frac-tions was determined using the phenol–sulphuric acid method (Dubois,Gilles,Hamilton,Rebers,&Smith,1956).The related frac-tions were pooled,dialyzed against distiled water,and lyophilized for further purifications.2.2.2.Purification and molecular weight determination of exo-polysaccharides by gelfiltrationThe fractions obtained from anion exchange chromatography were dissolved in elution buffer,10mM NaCl,filtered through a Milliporefilter(0.45l m),and applied to a Hiload™26/60Super-dex™200prep grade column(GE Healthcare,USA)coupled to a fast protein liquid chromatography system(FPLC,Pharmacia ÄKTA,Amersham Pharmacia Biotech,USA).Fractions of6ml were collected with a Fraction Collector Frac-900(Amersham Pharmacia Biotech,USA).The carbohydrate content in the fractions was deter-mined with the phenol–sulphuric acid method,and the related fractions were pooled.After dialysis and freezing-drying,the resulting six exo-polysaccharides of B-N-I,B-I-I,B-I-II,B-I-III,B-II-I and B-II-II,were obtained and subjected to further analyses.The molecular weight of the six exo-polysaccharides were determined and evaluated by gelfiltration on a Hiload™16/60 Superdex™200prep grade column(GE Healthcare,USA)coupled to a fast protein liquid chromatography system(FPLC,Pharmacia ÄKTA,Amersham Pharmacia Biotech,USA).Four micrograms of the samples were dissolved in2.0ml of10mM NaCl buffer,filtered through a Milliporefilter(0.45l m)and applied to the column.The column was eluted with10mM NaCl buffer at aflow rate of0.5ml/ min.Fractions of2.0ml were collected with a Fraction Collector Frac-900(Amersham Pharmacia Biotech,USA)and the eluent was monitored with a Shimadzu RI detector.The phenol–sulphuric acid method was employed to determine the carbohydrate elution profiles of the polysaccharides fractions.The column calibration was performed by various standard dextrans,with molecular weights of5.6,19,233and475kDa,respectively.plementfixating activityThe complementfixation test is based on inhibition of haemol-ysis in antibody sensitised sheep red blood cells(SRBC),by comple-ment from human sera(Michaelsen,Gilje,Samuelsen,Hogasen,& Paulsen,2000).Briefly,washed SRBC were sensitised with rabbit anti-SRBC antibodies(Vironamboceptor9020,Ruschlikon,Switzer-land),washed,and a1.0%cell suspension in veronal buffer contain-ing2mg/ml bovine serum albumin(BSA)and0.02%sodium azide (VB/BSA),was prepared.The human serum was diluted with VB/ BSA to a concentration resulting in50%haemolysis of the sensi-tised SRBC suspension.Samples were dissolved and serially dilutedB.-Z.Zhang et al./Food Chemistry163(2014)120–128121with VB/BSA.In a round bottom96-well microtiter plate,50l l of the sample solutions and50l l of the serum dilutions were added in duplicates to wells,and incubated in a shaker as described above.Then the sensitised sheep erythrocytes(50l l)were added and the microtiter plate was incubated for another30min.After being centrifuged at1000rpm for5min,100l l of the supernatant were transferred to aflat bottom microtiter plate and absorbance was measured at405nm by a microtiter plate reader.100l l of distiled water were mixed with50l l of sensitised sheep erythro-cytes to get a value of100%haemolysis.The mixture of VB/BSA, diluted serum and sensitised sheep erythrocytes was used as the medium control.A pectic polysaccharide,BP-II(=BP100III),from Biophytum petersianum Klotzsch was used as a positive control (Grønhaug et al.,2011).Inhibition of haemolysis induced by the test sample was calculated by the formula:Inhibition rate¼½A controlÀA m =A controlÂ100%where A control is the absorbance of the medium control and,A sample is the absorbance of the sample.2.4.Measurement of nitric oxide productionThe capacity of the isolated polysaccharides to stimulate macro-phages and produce nitric oxide(NO)was investigated according to the method described by Inngjerdingen et al.(2012).The mouse macrophage cell line,Raw264.7,was used in the experiments.LPS (from Pseudomonas aeruginosa10,Sigma–Aldrich,USA),and the polysaccharide Oc50A1.I.A from Opilia celtidifolia were used as positive controls(Grønhaug et al.,2010).The results are expressed as the mean±SD.The difference between the control,medium alone,and the treatment in these experiments was tested for sta-tistical significance by Dunnett’s Multiple Comparison Test.A value of p<0.05was considered as statistical significant.2.5.Determination of the monosaccharide compositionsThe polysaccharide samples were weighed exactlyand subjected to methanolysis with3M hydrochloric acid in anhy-drous methanol for24h at80°C.Mannitol was used as an internal standard.After methanolysis,the neutral sugars,methylesters and lactones of the uronic acids were converted into trimethylsilylated (TMS)derivatives of the methyl-glycosides.The monosaccharide compositions were determined by capillary gas chromatography on a Focus GC(Thermo Scientific,Milan,Italy)(Barsett,Paulsen, &Habte,1992).2.6.Determination of the protein contentThe protein contents of the polysaccharide samples were deter-mined using the Bio-Rad Bradford protein assay(Bio-Rad).The polysaccharides were dissolved in distiled water at a concentration of2.0mg/ml.A standard curve was prepared based on Bovine Serum Albumin(BSA).The samples were mixed with diluted dye reagent,incubated at room temperature for5min and the absor-bance was measured at595nm using a microtiter plate reader.2.7.Determination of the linkages of the polysaccharidesThe linkages were determined by performing a complete meth-ylation of the polysaccharide fractions,where methyl iodide was used as the methylation agent.Before methylation the uronic acids present were reduced to their corresponding neutral sugar by sodium borodeuteride on the polymer level.The fully methylated polysaccharides were then hydrolysed using2.5M trifluoroacetic acid,or90%(v/v)formic acid followed by reduction using sodium borodeuteride andfinally acetylated with ethyl acetate to generate partly acetylated,and partly methylated alditols(Kim&Carpita, 1992).The derivatives were analysed by GC/MS using a GCMS-QP2010,(Shimadzu,Japan)attached to a Restek Rxi-5MS(30m;0.25mm ID;0.25l mfilm)column.The injector temperature was 280°C,the ion source temperature was200°C and the interface temperature was300°C.The column temperature was80°C when injected,then increased by10°C/min to140°C,followed by4°C/ min to210°C and then20°C/min to300°C.Helium was the carrier gas(pressure control:80kPa).The compound at each peak was characterized by an interpretation of the retention times,and the characteristic mass spectra.The estimation of the relative amounts of each linkage type was related to the total amount of each mono-saccharide type as determined by methanolysis and GC.2.8.NMR analysis of the polysaccharidesNMR experiments were performed at600.13MHz(1H)and 150.90MHz(13C)on a Bruker AV600and a Bruker AVII600NMR spectrometer,both equipped with TCI(1H,13C,15N)cryo probes, with cold1H and13C preamplifiers.10mg of the sample was dis-solved in D2O(99.9%)to a total volume of0.5ml in5mm OD NMR tubes.The experiments were performed at60°C.Tuning and matching were performed with ATMM and shimming was per-formed with the gradient shim program TOPSHIM with normal z,x and y shimming before and after the gradient shimming procedure. 1H experiments were performed with NOESY-presat water suppression setting O1at the water resonance.The following experiments were recorded:1H(p)number of scans(NS)32.13C(zgpg30)NS15k.13C APT(jmod)NS10k. 1H13C HSQC(hsqcedetgp)NS32,Time domain(TD)(F2)4k,TD (F1)1k.1H13C HMBC(hmbcgplpndqf)NS256,TD(F2)4k,TD(F1) 256.1H1H COSY(cosygpqf)NS16,TD(F2)2k,TD(F1)512.The soft-ware Topspin2.1patch level6was used for acquisition and pro-cessing on Dell and HP PCs running Windows XP operating systems.3.Results and discussionPolysaccharides isolated from aqueous extracts of H.marmoreus fruiting bodies have previously been reported to possess antitu-mour activity(Ikekawa et al.,1992).However,Bao,Choi,and You (2010)reported that polysaccharides derived from fruiting bodies of H.marmoreus have almost no inhibition activity in the growth of a human gastric carcinoma cell line AGS,whereas sulphated polysaccharides exhibited inhibitory activity to the cell line AGS and immunomodulating activity,by inducing NO and cytokine (IL-1b and TNF-a)release from macrophages.Our previous study has shown that the crude exo-polysaccharides from fermentation broth of H.marmoreus exhibit potent inhibitory activity a against human gastric cancer cell line SGC-7901in vitro(Zhang et al., 2012).Therefore,further investigation of the exo-polysaccharide from the same cultivation of this mushroom was greatly of interest.3.1.Purification and molecular weight determinationExo-polysaccharides were separated from submerged cultiva-tion broth of the edible mushroom H.marmoreus after the pig-ments and proteins in the broth were eliminated(Scheme1).As shown in the scheme,the crude exo-polysaccharide B was fraction-ated by anion exchange chromatography.After equilibrated with distiled water,the neutral fraction B-N was eluted.The acidic frac-tions B-I and B-II were obtained from gradient elution.These three fractions were further purified by gelfiltration according to their size.As a result,the neutral exo-polysaccharide B-N-I was purified122 B.-Z.Zhang et al./Food Chemistry163(2014)120–128from B-N.Three exo-polysaccharides,B-I-I,B-I-II and B-I-III,were obtained from the acidic fraction B-I,while two exo-polysaccha-rides,B-II-I and B-II-II,were separated from B-II.Gelfiltration on a Hiload™16/60Superdex™200prep grade column was employed to determine the average M w of the purified exo-polysaccharides.The column was calibrated with dextran standards and the linear calibration curve wasfitted by the equation:lg M w¼À0:034Xþ7:155ðR2¼0:999ÞWhere M w is the molecular weight of the polymers(Da),X is the retention volume(ml),and R2is thefitting coefficient,which indi-cates the significance of the equation.The average molecular weights of four exo-polysaccharides B-N-I,B-I-I,B-II-I and B-II-II were investigated in the same chromato-graphic conditions and determined,according to the equation,to be6.3,120,150and11kDa respectively.Among them,B-I-I and B-II-I were the highest molecular weight exo-polysaccharides iso-lated from the acidic fractions B-I and B-II respectively.The results of the protein assays indicated that protein contents of these exo-polysaccharides are all less than1.0%.plementfixating activityIn the complementfixating assay the crude exo-polysaccharide, obtained from fermentation broth of H.marmoreus,and some of its isolated fractions exhibited strong human complementfixating activities in vitro,as shown in Fig.1A.The samples are compared with the positive control BP-II,a pectic fraction isolated from B. petersianum(Inngjerdingen et al.,2006).BP-II has previously shown to be highly active in the complementfixation assay,and typically shows a50%inhibition of hemolysis at10–20l g/ml. The concentrations of the polysaccharide samples giving50%of haemolysis(ICH50)are shown in Fig.1B.The crude exo-polysaccharide,B,and its acidic fractions B-I and B-II were more active than the positive control BP-II on weight basis.The observed activities were dose-dependent and their ICH50values were lower than that of BP-II,as shown in Fig.1B. The high molecular weight exo-polysaccharides of B-I-I and B-II-I,obtained from gelfiltration of the acidic fractions,exhibited the strongest complementfixating activities with ICH50values of5.8 and3.2l g/ml respectively.3.3.Measurement of nitric oxide(NO)production from macrophagesIn order to investigate the macrophage stimulating activities of the exo-polysaccharides,six exo-polysaccharides of B-N-I,B-I-I,B-I-II,B-I-III,B-II-I and B-II-II fractions obtained from gelfiltration were further investigated for their capacities to induce the release of NO from mouse macrophages,by the quantification of its stable breakdown product nitrite.The tests were performed in triplicate and the results are presented as mean values(Fig.2).As shown in Fig.2,all the six exo-polysaccharides induced a dose-dependent release of NO from mouse macrophages.When compared to the medium,the neutral exo-polysaccharide of B-N-I,the three acidic exo-polysaccharides of B-I-I,B-II-I and B-II-II, showed statistically significant stimulating effects on NO release from macrophages,at a concentration of100l g/ml.The two acidic exo-polysaccharides of B-II-I and B-II-II induced the strongest release of NO,followed by the neutral exo-polysaccharide of B-N-I and the acidic exo-polysaccharide of B-I-I,based on the results of significant analysis.No statistical significant NO production was observed in macrophages cultured with B-I-II and B-I-III.LPS is used as a positive control in present research for NO production from macrophages,and could induced significant release of NO at 0.5ng/ml.As some of the tested exo-polysaccharides did not show any activity in the NO-test system,even at100l g/ml,it is reason-able to anticipate that the active exo-polysaccharides were not contaminated during purification process by LPS.3.4.Carbohydrate compositions of the polysaccharidesAfter methanolysis and derivatization,the monosaccharide compositions of the polysaccharide fractions were analysed by GC and the results are shown in Table1.The main component of the neutral fraction(B-N)is glucose(Glc).However mannose (Man)and galactose(Gal)and other minor amounts of pentoses, were also present.The acidic fractions B-I and B-II showed major differences in their monosaccharide compositions.B-I is mainly composed of Man(68.8mol%),Gal(12.8mol%)and Glc (12.1mol%),while B-II has a more complicated monosaccharide composition.The main monosaccharide in B-II is galacturonic acid (GalA)(36.2mol%)with smaller amounts of arabinose(Ara), rhamonose(Rha),xylose(Xyl),Man,Gal and Glc.As shown in Tab.1,only the neutral exo-polysaccaride B-N-I exhibited similar monosaccharide compositions with its parent fraction,B-N,where high High amounts of Glc(82.3mol%)and minor amounts of Man (7.1mol%)and Gal(7.8mol%)are presented.Among the exo-poly-saccarides obtained from B-I after gelfiltration,the exo-polysacca-ride B-I-I with the highest molecular weight is mainly composed of Man(93.2mol%),while the lower molecular weight exo-polysacca-ride B-I-II consists of Ara,Rha,Gal,glucuronic acid(Glc A)and Gal A,all typical constituents in pectic polysaccharides.The lowest molecular weight exo-polysaccaride,B-I-III,is mainly composed of Glc and Man.Both of the exo-polysaccarides,B-II-I and B-II-II, obtained after gelfiltration of B-II contain a mixture of different monosaccharides.The main differences in the compositions are that Ara,Gal and GalA are the dominating monosaccharides in B-II-I,while those dominating in B-II-II are Rha,Glc and GalA.In the biological assays,the exo-polysaccharide B and its sub-fractions B-I,and in particular B-II,exhibited strong complement fixating activities,while the B-N fraction had weak activity (Fig.1).In consideration of monosaccharide compositions of these three fractions,we can notice that the active fractions,B-I and B-II, contain much less glucose than B-N,which possesses less complementfixating activity.A similar pattern,but less pro-nounced,was observed on the exo-polysaccharides obtained from gelfiltration.The most active exo-polysaccharides,B-I-I and B-II-I, only contain0.7and3.0%of glucose when the exo-polysaccharides,B.-Z.Zhang et al./Food Chemistry163(2014)120–128123B-N-I,B-I-III,B-II-II,contain much higher amounts of glucose and possess much less complement fixating activities.In previous reports,the most acidic fraction containing a great amount of Gal A isolated from Malian medicinal plant Trichilia emetica ,exhibited the highest complement fixating activities compared with the other fractions (Diallo et al.,2003).Similarly,an acidic polysaccha-ride fraction HAM-3-IIb-II,isolated from stems of Avicennia marina was characterized since it exhibited higher complement fixating activities than the other fractions containing smaller amounts of uronic acid (Fang,Jiang,&Wang,2006).It indicated that comple-ment fixating activities of the polysaccharides depends on the amounts of monosaccharide they contain,especially the amounts of glucose and uronic acid.It has been reported that acidic polysaccharides with higher molecular weights are most active in the complement fixating assay (Grønhaug et al.,2010).Among the three exo-polysaccha-rides purified from the B-I fraction,by gel filtration,exo-polysac-charide B-I-I (with the highest molecular weight)exhibited the strongest complement fixating activity.Similarly,the highest molecular weight exo-polysaccharide,B-II-I,purified from B-II fraction exhibited a higher complement fixating activity than exo-polysaccharide B-II-II,with lower molecular weight.These results suggest that high molecular weight might favour the com-plement fixating activity.A similar pattern was also observed when the NO production by macrophages,in response to thesix124 B.-Z.Zhang et al./Food Chemistry 163(2014)120–128exo-polysaccharides was analysed.As inducers of NO release,B-II-I (with highest molecular weight)was the most potent exo-polysac-charides.Among the exo-polysaccharides purified from B-I,B-I-I with the highest molecular weight was shown to induce the release of NO,while its sister exo-polysaccharides B-I-II and B-I-III did not induce any significant release of NO from macrophages.On the other side,the exo-polysaccharides of B-N-I and B-II-II with totally different monosaccharide compositions possessed low molecular weights at6.3and11kDa respectively,but exhib-ited different biological activities in the two assays used.B-N-I had a higher complementfixating activity,but a lower capacity for inducing macrophages to release NO,compared to B-II-II.This indicated that the bioactivities of the polysaccharides should not only be affected by molecular weight,but also be affected by monosaccharide compositions and some other molecular characteristics.3.5.Linkage compositions of the exo-polysaccaridesBased on the activities observed in the biological assays,four exo-polysaccharides B-N-I,B-I-I,B-II-I and B-II-II were applied to linkage and NMR analysis.The ratios of the linkages were calculated based on the monosaccharide compositions data and the areas of the methylated products divided by the mass of the products.The results are shown in Table2.In the neutral exo-poly-saccaride B-N-I,which is mainly composed of glucose,the inter linkage is mostly1?4with branching points mainly at position 6.Small amounts of1?2linked Man,1?4linked and1?3,4 linked Gal are also presented in B-N-I.The exo-polysaccaride B-I-I is a mannan in which the mannose units present are found as terminal,1?2,1?3and1?2,6linked residues.The linkage analysis revealed the acidic exo-polysaccarides B-II-I and B-II-II to be of highly complex natures.These two exo-polysaccarides contain similar types of glycosidic linkages.Both of the polymers have a main galacturonan chain being1?4linked with branchingpoints mainly at position3.Rha is1?2,4linked in both polymers, while B-II-II also contained1?2linked units.Gal units are found as terminal,1?3,1?4,1?6,1?3,4and1?3,6linked resi-dues.Terminally linked Glc A,and terminally,1?2and1?3 linked Man was only found in B-II-I.Furthermore,terminally and 1?5linked Ara,and terminally and1?2linked Xyl are more abundant in B-II-I compared to B-II-II.In B-II-II,higher amounts of Glc are present as terminal,1?3,1?4,1?6,1?4,6and 1?3,6linked residues.3.6.NMR spectroscopyNMR spectroscopy was used for the characterisation of the polysaccharides,especially for the determination of the anomeric configuration.B-N-I,the neutral polysaccharide,showed the presence of three major anomeric proton signals at d5.36,5.33and4.98,which were assigned as the proton at C1for the followingstructures:a-D-Glc p-(1?),a-D-Glc p-(1?4)and a-D-Glc p-(1?4,6),respectively in the1H NMR spectra.This is in good agree-ment with what recently was reported for a polysaccharideisolated from the mycelium of Flammulina velutipes(Yin et al.,2010).The chemical shifts ranging from3.4to4.0were designatedas signals related to the protons present on C2–C6.The anomericconfiguration was also confirmed by the three anomeric peaks inthe13C NMR spectrum of B-N-I,located at d102.8,102.6and101.6ppm.They are designated to C1of a-D-Glc p-(1?4)and a-D-Glc p-(1?6),a-D-Glc p-(1?4,6),and a-D-Glc p-(1?3,6),respec-tively.C6,as unsubstituted,was shown by the presence of signalsat63.5ppm and substituted C6with a signal at70.0ppm.Theintense signal at63.5ppm indicates long stretches of C6,asTable1Monosaccharide compositions(mol%)of the exo-polysaccharides obtained from H.marmoreus.Monosaccharide composition aB-N B-N-I B-I B-I-I B-I-II B-I-III B-II B-II-I B-II-IIAra 2.4 1.5 4.0 2.925.1 1.910.615.4 4.3 Rha Traces n.d.Traces n.d.7.2Traces12.67.417.8 Xyl 2.0 1.30.9 1.0Traces0.6 5.99.5 2.0 Man15.87.168.893.20.422.4 6.28.3 3.6 Gal8.17.812.8 2.435.48.317.921.310.9 Glc71.382.312.10.77.565.810.1 3.020.9 GlcA n.d.n.d.Traces n.d.8.6Traces0.6 1.7 1.7 GalA Traces Traces 1.3Traces15.8 1.136.233.338.9n.d.,not detected.a mol%of total carbohydrate content.Table2The linkages(mol%)of the monosaccharide present in the exo-polysaccaridesdetermined by GC–MS after methylation procedure and their M w.Glycosyl residues DeducedlinkagesMol%of methylated productsB-N-I B-I-I B-II-I B-II-IIAra T 1.17.9 2.71?57.51?4 1.7Rha T 2.61?28.81?30.9 1.61?2,4 5.5 4.9Xyl T 3.91?20.6 5.6 1.01?3,40.60.9Man T27.2 4.01?27.124.0 1.91?311.4 2.41?2,630.6Glc T18.4 1.5 5.61?3 2.61?453.7 6.21?6 2.0 1.6 2.61?4,67.2 1.51?3,6 1.1 2.3GlcA T 1.7Gal T0.6 6.2 4.61?4 2.6 3.6 2.21?3 2.70.91?60.9 1.60.71?3,4 3.3 2.7 2.31?3,6 4.70.6GalA T 2.11?416.316.21?3,416.919.51?2,4 1.1M w 6.3kDa120kDa150kDa11kDa B.-Z.Zhang et al./Food Chemistry163(2014)120–128125。
科技英语试题及答案
科技英语试题及答案一、选择题（每题2分，共20分）1. The term "nanotechnology" refers to the manipulation of matter on an atomic, molecular, and supramolecular scale.A. TrueB. False2. Which of the following is NOT a characteristic of renewable energy sources?A. Infinite in supplyB. Environmentally friendlyC. Dependent on weather conditionsD. Non-renewable3. The process of converting solar energy into electrical energy is known as:A. SolarizationB. Photovoltaic effectC. Solar distillationD. Thermal radiation4. In the context of computer science, what does "AI" stand for?A. Artificial IntelligenceB. Advanced InterfaceC. Automated InputD. Application Interface5. The term "genome" is associated with:A. The complete set of genes in an organismB. The structure of a cellC. The study of geneticsD. The process of cell division6. What is the primary function of a transistor in an electronic circuit?A. To amplify signalsB. To store dataC. To convert light into electricityD. To filter signals7. The "Internet of Things" (IoT) refers to:A. A network of interconnected devicesB. The global network of computersC. A collection of internet protocolsD. The study of internet security8. Which of the following is a type of biotechnology?A. Genetic engineeringB. Quantum computingC. NanolithographyD. Nuclear fusion9. The "Greenhouse Effect" is related to:A. The warming of the Earth's surfaceB. The cooling of the Earth's surfaceC. The process of photosynthesisD. The formation of the ozone layer10. What does "CRISPR" stand for in the field of molecular biology?A. Clustered Regularly Interspaced Short Palindromic RepeatsB. Computer-Aided Research in Scientific ProjectsC. Comprehensive Research in Innovative ScienceD. Computational Research in Systematic Processes二、填空题（每题1分，共10分）1. The unit of electrical resistance is the ______.2. The process of converting sound waves into electrical signals is known as ______.3. In physics, the term "entropy" is used to describe the level of ______ in a system.4. The study of the chemical composition of planets is known as ______.5. The term "cybersecurity" refers to the protection of______ from cyber threats.6. The process of converting electrical energy into light is known as ______.7. The smallest unit of life that can replicate itself is called a ______.8. The process of creating new substances from existing ones is known as ______.9. The study of the structure and function of cells is known as ______.10. The process of converting light energy into chemical energy is known as ______.三、简答题（每题5分，共30分）1. Explain the concept of "machine learning" in artificialintelligence.2. Describe the role of a semiconductor in modern electronics.3. What is the significance of biodiversity in the context of environmental science?4. Discuss the potential impact of nanotechnology on medicine.四、论述题（共40分）1. Discuss the ethical considerations involved in the development and use of genetic engineering technologies. (20分)2. Analyze the potential benefits and challenges of implementing a global Internet of Things (IoT) network. (20分)答案：一、选择题1. A2. D3. B4. A5. A6. A7. A8. A9. A10. A二、填空题1. ohm2. transduction3. disorder4. cosmochemistry5. information systems6. electroluminescence7. cell8. synthesis9. cytology10. photosynthesis三、简答题1. Machine learning is a subset of artificial intelligence that enables computers to learn from and make decisions based on data, improving at tasks over time through experience without being explicitly programmed.2. Semiconductors are materials with electrical conductivity between that of a conductor and an insulator. They arecrucial in electronic devices like transistors and diodes, allowing for the control of electrical current and the amplification of signals.3. Biodiversity is significant in environmental science as it ensures the stability of ecosystems, supports ecological processes, and provides a variety of services and resources that are vital for human survival and well-being.4. Nanotechnology has the potential to。
大蒜多糖提取、结构测定、化学修饰及生物活性研究进展
代爽，李琳琳，尹卫，等. 大蒜多糖提取、结构测定、化学修饰及生物活性研究进展[J]. 食品工业科技，2024，45（1）：9−17. doi:10.13386/j.issn1002-0306.2023060161DAI Shuang, LI Linlin, YIN Wei, et al. Research Progress on Extraction, Structure Determination, Chemical Modification and Biological Activity of Garlic Polysaccharides[J]. Science and Technology of Food Industry, 2024, 45(1): 9−17. (in Chinese with English abstract). doi: 10.13386/j.issn1002-0306.2023060161· 特邀主编专栏—食品中天然产物提取分离、结构表征和生物活性（客座主编：杨栩、彭鑫） ·大蒜多糖提取、结构测定、化学修饰及生物活性研究进展代 爽1,2，李琳琳1,2，尹 卫1，王 乐1，王煜伟1, *，梁 健1,*（1.青海大学省部共建三江源生态与高原农牧业国家重点实验室，青海西宁 810016；2.青海大学农牧学院，青海西宁 810016）摘 要：作为大蒜的主要活性成分之一，大蒜多糖具有增强免疫力、抗菌、抗病毒、抗氧化、保肝、降血脂、降血糖等多种生物活性，应用前景广阔。
大蒜多糖的提取方法以热水法、酶法和超声辅助法最为常见，大蒜多糖是由果糖、葡萄糖、半乳糖、甘露糖、半乳糖醛酸等组成的杂多糖，乙酰化、硒化和磷酸化等化学修饰可以增加大蒜多糖抗氧化等生物活性。
本文从大蒜多糖的提取、结构测定、化学修饰及生物活性的角度出发，系统总结了大蒜多糖的研究现状，未来应关注多糖结构与生物活性的构效关系，深入探讨大蒜多糖的功效机理，以期为大蒜多糖作为功能性产品的开发利用提供理论参考。
配体取代基、金属离子和溶剂对配位聚合物结构的影响
厦门大学硕士学位论文配体取代基、金属离子和溶剂对配位聚合物结构的影响姓名：周东生申请学位级别：硕士专业：无机化学指导教师：杨士烑20090701 厦门大学理学硕上学位论文摘要本文采用锌、锰、铜、钻、镍离子和芳香羧酸配体在水热、溶剂热等合成条件下，合成了１８个配位聚合物，对其晶体结构和相关性质进行了分析测试，并根据反应条件与合成产物之间的关系，讨论了配体取代基、金属离子及溶剂对配位聚合物组装规律的影响。
本论文内容包括以下六个方面：１．以ｚｎ２＋为中心离子，在吡啶参与下，通过改变间苯二甲酸的５位取代基在水热条件下合成得到三个不同的配位聚合物。
结果表明，当羧酸苯环上的５位取代基从一Ｈ、一０Ｈ到一纪，．卜Ｂｕ，产物中锌离子的配位数逐渐减小，产物维数逐渐降低，配体非配位基团位阻增大导致了金属配位数和产物维数的不同。
２．以Ｃｕ２＋为中心离子，通过改变间苯二甲酸的５位取代基在溶剂热条件下合成得到四个不同的配位聚合物。
结果表明，当羧酸苯环上的５位取代基从一ＯＨ、一Ｈ、一Ｎ０２到一招力．Ｂｕ，反应产物结构分别从球状结构到２Ｄ平面结构，取代基亲水性减小、位阻增大引起了次级结构单元与配体在空间排列上不同，导致聚合物结构的不同。
３．采用５－叔丁基间苯二甲酸（Ｈ２ｔｂｉｐ）和４，４‟．联吡啶（４，４‟－ｂｐｙ）为配体，改变金属离子在水热反应条件下进行自组装、合成了两个不同的配位聚合物。
结果表明，Ｍｎ２＋采取六配位方式，而ｚｎ２＋采取四配位和六配位两种方式，反应产物结构分别为１Ｄ链和２Ｄ平面结构。
金属离子不同、金属离子半径不同，导致了配位数目不同，获得不同结构的配位聚合物。
４．采用４，４‟．联苯二甲酸为配体，通过改变金属离子在溶剂热反应条件下进行自组装，合成得到两个不同的配位聚合物。
由于Ｍｎ２＋与Ｃ０２＋金属离子半径不同、配位数目不同，分别得到了３Ｄ网络结构与２Ｄ平面结构。
５．以２．硝基对苯二甲酸和钴离子在不同溶剂（ＤＭＳＯ、Ｈ２０／ＤＭＡ、Ｈ２０）中合成了三个不同的配位聚合物。
新教材同步备课2024春高中生物第3章基因的本质3.3DNA的复制课件新人教版必修2
(2)注意碱基的单位是“对”还是“个”。 (3)切记在DNA复制过程中，无论复制了几次，含有亲代脱氧 核苷酸单链的DNA分子都只有两个。 (4)看清试题中问的是“DNA分子数”还是“链数”，“含” 还是“只含”等关键词，以免掉进陷阱。
二、DNA分子的复制
例1.某DNA分子中含有1 000个碱基对(被32P标记)，其中有胸腺 嘧啶400个。若将该DNA分子放在只含被31P标记的脱氧核苷酸的 培养液中让其复制两次，子代DNA分子相对分子质量平均比原来 减少 1 500 。
F2:
提出DNA离心
高密度带 低密度带 高密度带
低密度带 高密度带
一、DNA复制的推测—— 假说-演绎法
1.提出问题 2.提出假说
（1）演绎推理 ③分散复制
15N 15N
提出DNA离心
P:
3.验证假说
15N 14N
F1:
细胞分 裂一次
转移到含 14NH4Cl的培养 液中
提出DNA离心
细胞再 分裂一次
二、DNA分子的复制
例3.若亲代DNA分子经过诱变，某位点上一个正常碱基变成了5-溴 尿嘧啶（BU），诱变后的DNA分子连续进行2次复制，得到4个子 代DNA分子如图所示，则BU替换的碱基可能是（ C ）
A.腺嘌呤 C.胞嘧啶
B.胸腺嘧啶或腺嘌呤 D.鸟嘌呤或胞嘧啶
二、DNA分子的复制
例4. 5-BrU(5-溴尿嘧啶)既可以与A配对，又可以与C配对。将一 个正常的具有分裂能力的细胞，接种到含有A、G、C、T、5-BrU 五种核苷酸的适宜培养基上，至少需要经过几次复制后，才能实现 细胞中某DNA分子某位点上碱基对从T—A到G—C的替换（ B ）
结构形态与建筑造型关系研究——以桁架结构为例
筑造型与结构形态很难契合。
事实上，结构不仅承载着支撑荷载的作用，其本身也清晰地反映了静力的传递方式，因而其在建筑中展现了形与力的特质。
正如自然界中的结构，如表面张力巨大的水泡、肥皂泡和水滴，空中悬吊的蜘蛛网，植物上翻的叶片，被大雪压弯的树枝等，都以特定的结构形态反映了受力的特点。
正因结构对于建筑存在“力场”的呈现作用，因而在建筑设计中，结构形态的设计会给建筑造型带来至关重要的影响。
本文将提出“以结构为先导”的策略，结合桁架建筑案例，探讨结合结构进行建筑创作的可能性。
2从建筑师与工程师的分化看结构作用变迁12—13世纪战争时期，工程师这一名词是欧洲城塞建设者的称呼，法国的柯尔（Kohl）则最先将工程师（engineer）与建筑师（architect）区分开来。
17世纪时，工兵将校被称为工程师。
18世纪中叶，随着第一次工业革命的爆发，社会分工细化，传统建造师的职责被分为建筑师、土木工程师和建造工程师[1]。
在建筑和结构分化的不到200年的历史中，结构形态和建筑造型的研究历史更加短暂。
1824年波特兰水泥被发明，1853年钢筋混凝土第一次应用于结构工程。
材料的发展使得建筑师有了更多的创作余地。
20世纪初，P. L. 奈尔维（P. L. Nervi）凭借其敏锐的结构直觉和对材料的熟悉，在精密计算还没有成熟的时期，创作出优美的钢筋混凝土作品，他充分发挥了混凝土材料在大跨度结构中的潜力，同时也表达了建筑的美和建造方法的巧妙。
奈尔维在他的《建筑的艺术与技术》一书中探索技摘要 随着对结构设计的认识更加深入，结构因其力学性质所展现的丰富形态引起了建筑师的注意，结构也从传统的承重角色转变成建筑设计的重要因素。
在进行建筑造型的构思和设计时，也应对其结构设计进行更深入的研究。
本文以结构设计为先导的设计为起点，以运用桁架结构的建筑为例证，探讨结构形态与建筑造型的统一性。
关键词 结构形态；建筑造型；桁架中图分类号 TU-80 文献标识码 A基金项目 国家自然科学基金项目资助（5207081107）。
不对称自由基反应英文
不对称自由基反应英文Asymmetric Radical Reactions: An Insight into Their Mechanism and Applications.Introduction.Asymmetric radical reactions have emerged as a powerful tool in organic synthesis, enabling the synthesis of chiral compounds with high enantiomeric purity. These reactions differ significantly from their symmetric counterparts, as they involve the generation and utilization of chiral radicals. These chiral radicals can undergo a range of reactions, including substitution, addition, and cyclization, leading to the formation of enantiomerically enriched products.Mechanism of Asymmetric Radical Reactions.The mechanism of asymmetric radical reactions typically involves three key steps: radical generation, chiralitytransfer, and radical termination.Radical Generation.The first step involves the generation of a radical species. This can be achieved through various methods, such as photolysis, thermal decomposition, or redox reactions. The generated radical can be chiral or achiral, depending on the starting materials and the conditions used.Chirality Transfer.The second step involves the transfer of chirality from a chiral auxiliary or catalyst to the radical species. This chirality transfer can occur through covalent or non-covalent interactions between the catalyst/auxiliary and the radical. The nature of these interactions determines the stereoselectivity of the reaction.Radical Termination.The final step involves the termination of the radicalspecies, leading to the formation of the desired product. This termination can occur through various mechanisms, such as coupling with another radical species, hydrogen atom abstraction, or disproportionation.Applications of Asymmetric Radical Reactions.Asymmetric radical reactions have found widespread applications in various fields of organic synthesis, including the synthesis of natural products, pharmaceuticals, and functional materials.Synthesis of Natural Products.Natural products often possess complex chiral structures, making their synthesis challenging. Asymmetric radical reactions have proven to be effective tools for the synthesis of such chiral natural products. For example, the use of chiral radicals generated from appropriate precursors has enabled the enantioselective synthesis of alkaloids, terpenes, and amino acids.Pharmaceutical Applications.The enantiomers of chiral drugs often differ significantly in their biological activities, making it crucial to control their enantiomeric purity. Asymmetric radical reactions can be used to synthesize enantiomerically enriched chiral drugs with high selectivity. This approach has been successfully applied to the synthesis of various drugs, including anti-inflammatory agents, anticancer agents, and antiviral agents.Functional Materials.Chiral materials possess unique physical and chemical properties that make them useful in various applications, such as displays, sensors, and catalysts. Asymmetricradical reactions can be used to synthesize chiral building blocks for the preparation of such materials. For instance, chiral polymers can be synthesized by utilizing asymmetric radical polymerization reactions, leading to the formation of materials with controlled chirality and tailored properties.Conclusion.Asymmetric radical reactions have emerged as powerful tools for the synthesis of enantiomerically enriched chiral compounds. Their unique mechanism, involving chirality transfer from a chiral catalyst/auxiliary to the radical species, enables high selectivity and enantiopurity in the product. The widespread applications of asymmetric radical reactions in organic synthesis, particularly in the synthesis of natural products, pharmaceuticals, and functional materials, highlight their importance in modern chemistry.Future Perspectives.Despite the significant progress made in the field of asymmetric radical reactions, there are still numerous challenges and opportunities for further exploration.Improving Selectivity and Efficiency.One of the key challenges in asymmetric radical reactions is achieving high selectivity and efficiency. While significant progress has been made in this area, there is still room for improvement. Future research could focus on developing new chiral catalysts/auxiliaries that can promote asymmetric radical reactions with higher selectivity and efficiency.Expanding the Scope of Reactions.Currently, the scope of asymmetric radical reactions is limited by the availability of suitable precursors and the reactivity of the generated radicals. Future research could aim to expand the scope of these reactions by developing new methods for generating radicals with desired functionalities and reactivities.Applications in Sustainable Chemistry.In the context of sustainable chemistry, asymmetric radical reactions offer an attractive alternative to traditional synthetic methods. By utilizing renewableresources and mild reaction conditions, asymmetric radical reactions could contribute to the development of more sustainable synthetic routes for the preparation of chiral compounds.Integration with Other Techniques.The integration of asymmetric radical reactions with other techniques, such as photocatalysis, electrochemistry, and microfluidics, could lead to the development of new and innovative synthetic methods. By combining the advantages of these techniques, it may be possible to achieve even higher selectivity, efficiency, and scalability in asymmetric radical reactions.In conclusion, asymmetric radical reactions have emerged as powerful tools for the synthesis of enantiomerically enriched chiral compounds. While significant progress has been made in this area, there are still numerous opportunities for further exploration and development. Future research in this field could lead tothe discovery of new and innovative synthetic methods with improved selectivity, efficiency, and sustainability.。
华中科技大学二〇一五年招收硕士研究生入学考试试题
华中科技大学二〇一五年招收硕士研究生入学考试试题考试科目：338生物化学适用专业：生物学一、写出下列名词对应的中文并解释(40分，每题4分)1、configuration & conformation2、structural domain ＆super-secondary structure3、allosteric effect ＆hyperchromic effect4、liposome & ribosome5、molecular chaperone & molecular hybridization6、0RF & ARS7、transposition & semiconservative replication8、frameshift mutation & nonsense mutation9、intron & operon10、zinc finger & basic-leucine Zipper二、填空题(34分，每空1分)1、天然淀粉一般含有两种组分：_____和_____,前者易溶于水，形成稳定的胶体；后者仅少量溶于热水。
2、由于细胞壁的化学组成和结构不同将细菌分成两大类：能保留革兰氏染色的称_____,不能保留的称______。
3、胞壁肽是一个含有四肽侧链的二糖单位，二糖单位由β-1,4连接的______和_________组成，四肽侧链的N端通过酰胺键与_____残基的乳糖基相连。
4、糖胺聚糖中结构最简单与其他糖胺聚糖有很大不同的是_____。
5、18:2△9c,12c指_:18:3△9c,12c,15c指_。
6、油脂的不饱和程度通常用_______来表示；在催化剂如Ni的存在下油脂中的双键与氢发生加成称______。
7、____为类固醇类化合物的核心结构；___为鞘糖脂的核心化合物。
8、脂蛋白依密度增加为序可分为_、_____、_____、_____和_____。
First-principles study of the structural, vibrational, phonon and thermodynamic
1. Introduction Ultra-high temperature ceramics (UHTCs) with melting temperatures in excess of 3000 K are usually composed by the refractory borides, carbides and nitrides of early transition metals [1–7]. Among the UHTCs, transition metal carbides (TMC) such as TiC, ZrC and HfC are metallic compounds with unique physical and chemical properties including an extremely high melting point and hardness, chemical stability, corrosion resistance combined with metallic electrical and thermal conductivities [5–10]. These features give transition metal carbides the capability to withstand high temperatures in oxidizing environments, making them candidates for applications in the atmosphere of extreme thermal and chemical environments [6,7]. The structural, vibrational, phonon and thermodynamic properties of IVb group transition metal carbides have been investigated experimentally [10–17] and theoretically [13,18–28] in the earlier reports. In the 1970s, the phonon dispersion relations of TiC, ZrC and HfC were measured using inelastic neutron scattering by Pintschovius et al. [10] and Smith et al. [15–17]. Lattice dynamics calculation and the phonon dispersion relations of transition metal carbides such as ZrC and HfC were reported using a phenomenological ‘‘double-shell’’ model theory [18] where long-range interatomic interactions were taken into account in order to get a
极固宁舒适达联合使用治疗中老年患者牙本质过敏症的临床疗效观察
247表 两组患者治疗情况比较（x -±s）组别例数术中出血量（ml）手术时间（min）住院费用（万元）脊柱JOA 评分（分）Cobb 角（°）观察组56187.5±12.651.8±4.9 1.0±0.282.6±3.17.1±1.2对照组50439.8±27.579.5±5.8 1.9±0.286.5±3.07.1±1.3t -- 4.1628.021 6.32716.58412.145P--＜0.05＜0.05＜0.05＞0.05＞0.053 讨论胸腰椎段骨折在临床上具有较高的发病率，可将其按照损伤严重程度分为压缩性骨折、分离损伤、旋转或多方向不稳定损伤三种。
临床上治疗是首选手术方式，但是因为手术方式较多，具体采用哪种手术方式存在较大的异议[2]。
本次对我院收治的106例胸腰椎B 型骨折患者进行手术治疗，结果显示，两组患者在脊柱J O A 评分和Cobb 角方面比较无差异性（P ＞0.05），无统计学意义；但观察组患者的术中出血量、手术时间以及住院费用均显著低于对照组，存在较大差异性（P ＜0.05），有统计学意义，说明经伤椎单节段和跨伤椎短节段治疗胸腰椎B 型骨折患者的临床效果差异性不明显，但是经伤椎单节段在手术时间、住院费用以及术中出血量上占有一定的优势，容易被患者所接受。
这是因为经伤椎固定术避免了术后应力的相对集中，避免了上下椎体前缘之间距离的缩短，同时避免了固定后侧向不稳定以及抗旋转性较差的情况[3]。
综上所述，胸腰椎B 型骨折经伤椎单节段与跨伤椎短节段固定的临床疗效相当，而经伤椎单节段固定术具有微创、医疗费用低等优点，目前在临床上广泛使用。
【参考文献】[1]崔尚斌，魏富鑫，刘少喻，等.胸腰椎B 型骨折经伤椎单节段与跨伤椎短节段固定的对比研究[J].中国组织工程研究，2014，10(17):2709-2715.[2]李清华.经伤椎单节段与跨伤椎短节段固定胸腰椎B 型骨折的临床疗效分析[J].中外女性健康研究，2015，8(11):169，167.[3]罗乐.胸腰椎B 型骨折实施不同固定治疗(经伤椎单节段、跨伤椎短节段)效果对比[J].饮食保健，2017，4(18):25-26.牙本质过敏症是在口腔科门诊中常见的一种症状，是牙体硬组织非龋性疾病。
向心结构和离心结构举例说明英语
向心结构和离心结构举例说明英语向心结构（Centripetal Structure）是指文章结构向着核心逐渐聚拢的结构，即文章开头通常是广泛而泛泛地叙述，而后缓缓进入重点，最后一步步逼近主题。
下面给出一篇使用向心结构的文章例子：Title：The Importance of a Good Night's Sleep。
Introduction：Sleep is essential to our health and well-being. In fact, it is just as important as a healthy diet and regular exercise. Yet, many of us overlook the importance of a good night's sleep.Body Paragraph1：Firstly, lack of sleep can have serious consequences on our physical health. People who do not get enough sleep are at a higher risk of developing heart disease, high blood pressure, and diabetes.Body Paragraph2：Secondly, poor sleep also affects our mental health. Lack of sleep can lead to anxiety, depression, and other mental health problems.Body Paragraph3：Finally, getting enough sleep is crucial for our daily functioning. It helps us feel alert, focused, and productive throughout the day.Conclusion：In conclusion, getting a good night's sleep is essential for our physical and mental health, as well as our daily functioning. We should prioritize getting enough sleep just as we prioritize a healthy diet and regular exercise.离心结构（Centrifugal Structure）是指文章结构由核心向外逐渐展开，即文章开头先阐述一个主题，然后通过举例、解释等手段逐渐拓展出更多细节。