Synthetic and biological studies on a cyclopolypeptide of plant origin     

Dahiya R  Kumar A 《Journal of Zhejiang University. Science. B》2008,9(5):391-400

Objective: A natural cyclic peptide previously isolated from Citrus medica was synthesized by coupling oftetrapep-tide units Boc-Leu-Pro-Trp-Leu-Ome and Boc-Ile-Ala-Ala-Gly-Ome after proper deprotection at carboxyl and amino terminals followed by cyclization of linear octapeptide segment.Methods: Solution phase technique was adopted for the synthesis of cyclooctapeptide--sarcodactylamide.Required tetrapeptide units were prepared by coupling of Boc-protected dipeptides viz.Boc-Leu-Pro-OH and Boc-Ile-Ala-OH with respective dipeptide methyl esters Trp-Leu-Ome and Ala-Gly-Ome.Cyclization of linear octapeptide unit was done by p-nitrophenyl ester method.The structure of synthesized cyclopolypeptide was elucidated by FTIR,1H NMR,13C NMR,FABMS spectral data and elemental analysis.The newly synthesized peptide was evaluated for dif-ferent pharmacological activities including antimicrobial,anthelmintic and cytotoxic activities.Results: Synthesis of sarcodac-tylamide was accomplished with >78% yield utilizing dicyclohexylcarbodiimide (DCC) as coupling agent.Newly synthesized peptide possessed potent cytotoxic activity against Dalton's lymphoma ascites (DLA) and Ehrlich's ascites carcinoma (EAC) cell lines,in addition to moderate anthelmintic activity against earthworms Megascoplex konkanensis,Pontoscotex corethruses and Eudrilus sp.Moreover,cyclopolypeptide displayed good antimicrobial activity against pathogenic fungi Candida albicans and Gram-negative bacteria Pseudomonas aeruginosa,in comparison to standard drugs griseofulvin and ciprofloxacin.Conclusion: Solution phase technique employing DCC and triethylamine (TEA) as base proved to be effective for the synthesis of natural cyclooctapeptide.N-methyl morpholine (NMM) was found to be a better base for the cyclization of linear octapeptide unit in comparison to TEA and pyridine.  相似文献   

职业教育基本问题访谈录(I) 职业教育是什么     

王明达  杨金土  刘来泉  余祖光  高奇  Josie Misko  Susan Dave  Jorn Saunder  钱景舫  Friedhelm Eicker  James R Stone 《中国职业技术教育》2006,(14)

全国教育科学“十五”规划国家一般课题《职业教育几个基本问题研究》(BJA010100)课题组就“职业教育的基本问题”对国内外职业教育界的专家、学者进行了访谈,使我们看到了对此问题的不同角度和层面的理解。这是一次思想的碰撞,有利于我们深化对职业教育基本问题的认识。本刊特将访谈记录分专题编辑处理,并从本期起连续刊发,本期论题为“职业教育是什么?”  相似文献   

Many ways of telling: expanding conceptualizations of child sexual abuse disclosure     

Alaggia R 《Child abuse & neglect》2004,28(11):1213-1227

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生物学教科书中的错误和概念不正确：细胞生理学     

Store.  R 朱善良 《生物学教学》1993,(4):4-7

本文是关于教科书中的错误和概念不正确以及过时提法的系列文章中的第五篇,供中学和大学普通生物学课程教师阅读。第一篇是关于光合作用的、第二篇关于细胞结构、第三篇关于细胞的新陈代谢、第四篇关于细胞能力学。写作这一系列文章的目的以前曾作过说明。本文讨论教科书中有关细胞功能方面常被误解、或被忽略的问题。  相似文献   

英国《化学习题精选》(一)     

J.R.L.Swain  J.S.Charke  张伟敏 《化学教学》1981,(4)

《化学习题精选》是英国中学化学教师为学生提供复习和提高作业质量而编的。它的特点有:1.围绕题目编成一系列短小的问题。这些问题系按照英国现用的教材结构编写的;由浅入深,由易到难,逐步引导学生的学习兴趣;可在课内外用作讨论或练习之用。2.作者将各小题划分为三种类型:(1)知识性(以K表示),理解性(以C表示)及综合性(以H表示)。每小题都注明评分标准,用以了解学生的知识水平和分析问题、解决问题的能力。本书共有一百题,我们根据我国中学化学教学大纲的内容选译部分习题,供教师们参考、选用。选译习题中也略有超我国教材水平的,可作因材施教之用。习题的后面,附有用数字回答问题的答案。  相似文献   

亨利福特社区大学协作性教学方法     

Bailey  R  刘湘生 《职教译丛》2000,(4):30-32

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How Improve Your Teaching     

Charlatte·R·Petres 《教学与管理》1991,(6)

The avenue by which we Learn are differentSome people Learn throngh, hearing others throughseeing, antd Some use a combination of the two.However for many that isn't enough. They mustuse these ways plus speaking and writing. studiesShow that the stmost effective method of learning isto practice what has bbeenaquired. An ameia the trend. has moved from lecture toclass participation. Stu -- dents earn letter gradeswhen they have the opportunity to ask questions, toform Small discussion groups, to role play, to ex-press ideas in writing and in Song, and even to en-gage in games that are related to the lesson.  相似文献   

Disaster in the making     

Nowak R 《New scientist (1971)》2001,169(2273):4-5

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The etiology of mathematical self-evaluation and mathematics achievement: understanding the relationship using a cross-lagged twin study from age 9 to 12     

Luo YL  Kovas Y  Haworth CM  Plomin R 《Learning and individual differences》2011,21(6):710-718

The genetic and environmental origins of individual differences in mathematical self-evaluation over time and its association with later mathematics achievement were investigated in a UK sample of 2138 twin pairs at ages 9 and 12. Self-evaluation indexed how good children think they are at mathematical activities and how much they like those activities. Mathematics achievement was assessed by teachers based on UK National Curriculum standards. At both ages self-evaluation was approximately 40% heritable, with the rest of the variance explained by non-shared environment. The results also suggested moderate reciprocal associations between self-evaluation and mathematics achievement across time, with earlier self-evaluation predicting later performance and earlier performance predicting later self-evaluation. These cross-lagged relationships were genetically rather than environmentally mediated.  相似文献   

The comprehension and production of Wh-questions in deaf and hard-of-hearing children     

Friedmann N  Szterman R 《Journal of deaf studies and deaf education》2011,16(2):212-235

Hearing loss during the critical period for language acquisition restricts spoken language input. This input limitation, in turn, may hamper syntactic development. This study examined the comprehension, production, and repetition of Wh-questions in deaf or hard-of-hearing (DHH) children. The participants were 11 orally trained Hebrew-speaking children aged 9.1-12.4 with moderate-to-profound hearing loss from birth, who consistently used hearing aids or cochlear implants and who had difficulties understanding relative clauses. Experiment 1 tested the comprehension of Wh-questions using a picture selection task, comparing subject with object questions and who- with which-questions; Experiment 2 tested the production of subject and object who-questions using an elicitation task; and Experiment 3 tested the repetition of Wh-questions and other structures derived by Wh-movement. All the DHH participants showed difficulty in the comprehension, production, and repetition of object questions, and their performance was significantly below that of hearing children. In contrast, they repeated embedded sentences without movement well, indicating that their deficit is in syntactic movement rather than embedding or the CP node in the syntactic tree. The results provide additional evidence that DHH children have difficulties with Wh-movement and emphasize that Wh-questions, which are crucial for communication, can be severely impaired in these children.  相似文献