Synthetic and biological studies on a cyclopolypeptide of plant origin

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.     

"熵"的科学定义

“熵”是热学中一个极其重要的基本概念，追溯它的起源，从物理定义的“完备性”要求，对“熵”从宏观到微观，从“定性”到“定量”分别进行了定义。     

数学起源对新课标下数学教学的启发

借数学思想萌芽阶段——常量数学起源的探索,为中学数学教师们在新课程标准下的教学带来一点借鉴和参考.     

劳动分工与企业起源

企业是以内部具有分工协作关系的团队生产为基础、为交换而生产的经济组织,分析企业的性质必须包括技术关系和经济关系两方面的内容。社会分工体系的发达,劳动组织内对工序和操作的细分以及基于操作专业化的各工序与操作的劳动协作,是企业产生的决定因素。所谓企业起源问题,从历史上说也就是资本主义手工工场和工厂的产生过程。     

恒星的一生

恒星是由星际漫物质在万有引力作用下集聚形成的，由氢氦元素的聚变反应热维持其生命过程，在历经主序星，红巨星和白矮星或中子星后演化为致密星体而结束一生。这种演化过程对应着它在赫罗图上位置的规律性变动。     

探析近代专利制度起源于英国的原因

世界上第一部专利法是威尼斯共和国的专利法,但是近代专利制度却不是起源于此,而是以英国1624年的专利法规作为近代专利制度起源的标志,本文试图分析其中的原因.     

对乡村旅游起源及概念的探讨

近年来乡村旅游的发展非常迅猛,为城市居民提供了新的旅游休闲地域与空间,也为农民致富和农村发展开辟了新的途径.本文探讨了乡村旅游的起源,并在比较众多学者给出的乡村旅游概念基础上,尝试性地界定乡村旅游概念.     

我国远程教育的起源、现状和发展趋势

我国的远程教育从函授教育、广播电视教育,发展到今天的以计算机网络为主的双向交互电子通讯教育,成为我国实施"科教兴国"战略,面向21世纪发展高等教育事业,构建学习型社会的一项重要的基础性系统建设。它必将通过构建新型的人才培养模式对我国综合国力和国际竞争力的提高,以及全面实现小康社会产生重要的影响。     

生物多样性保护与人类的关系

介绍了生物多样性的三个层次,即生态系统多样性、物种多样性和遗传多样性,及其主要含义、主要研究内容.并简要讨论了生物多样性保护研究的重要性,以引起人们对日益恶化的环境给予重视,共同保护我们的生存环境,保护生物多样性.