Natural products chemistry in the marine environment

Significant differences and numerous similarities exist in the biosynthetic activities of marine and terrestrial plants and animals. While the more primitive marine biota are recognized to possess the common biosynthetic pathways to produce terpenes, acetogenins, aromatic compounds, and alkaloids, in many cases these pathways have been modified in unusual ways. The halogens in sebwater, for example, appear to be fundamentally involved in terpene biosynthesis and in the production of bromine-containinq acetogenins and phenolic compoupds. Marine metabolites have high physiological activities, and these molecules are conceived to function, in part at least, as defensive adaptations In the marine environment.     

自然资源与自然环境

本文从理论上探讨自然资源与自然环境的基本概念、基本特性及它们之间的区别和联系,进而指出树立资源开发与环境保护新观念的必要性。     

Natural language processing

Natural language processing (NLP) is the study of mathematical and computational modeling of various aspects of language and the development of a wide range of systems. These include spoken language systems that integrate speech and natural language; cooperative interfaces to databases and knowledge bases that model aspects of human-human interaction; multilingual interfaces; machine translation; and message-understanding systems, among others. Research in NLP is highly interdisciplinary, involving concepts in computer science, linguistics, logic, and psychology. NLP has a special role in computer science because many aspects of the field deal with linguistic features of computation and NLP seeks to model language computationally.     

创新产品与技术

技术创新一直是推动行业发展的源动力，为使国内温室公司相关技术人员与研究部门的专家学者及时了解与掌握国际温室创新产品与技术的最近进展，本刊与美国著名园艺杂志Greenhouse Grower合作，从本期开始开设“创新产品与技术”专栏，陆续将该刊所刊载的相关创新产品与技术信息传递给国内广大读者。[编者按]     

Biosynthesis of natural products

The experimental verification of a proposed biosynthetic pathway for a given natural product is often difficult to obtain with the use of the whole organism (permeability factors) or, in the case of higher plants, a cell-free system. Until the purified enzyme for each step of biosynthesis is available, biosynthetic studies can, however, be carried out, albeit with modest incorporation values, by means of either hydroponic or injection methodology. Where viable seed sources are available it is suggested that improvements of several orders of magnitude in incorporation can be achieved by a short-term incubation (small pool size of precursors; trapping of reactive intermediates) or a long-term feeding (equilibration of precursor with the compartmentalized or induced synthetases). In bacterial, fungal, mammalian, and plant systems, where incorporation efficiencies provide the opportunity to study (13)C enrichment (at least equal to natural abundance of the isotope), we can expect a rapid expansion since the method removes the tedium of carbon-by-carbon degradation. For the next few years, however, the prognosis would seem to favor parallel studies of (13)C and (2)H, and of (14)C/(3)H ratio techniques since the last-mentioned method provides more information concerning the stereoselectivity of labeling processes on the microgram scale.     

天然番茄红素的稳定性研究

为有效开发番茄工素，研究了不同条件下天然番茄红素的稳定性。结果表明：Fe^3 和Cu^2 对番茄红素的稳定性影响较大，NaOH对番茄红素的稳定性有较大的破坏作用，在酸性条件下比较稳定；氧化剂、还原剂和防腐剂对番茄红素的稳定性影响非常小，抗氧化剂能延缓番茄红素的损失；番茄红不比对光十分敏感，尤其是日光下直射1d即可完全损失，对紫外光和白炽灯光也较敏感；低于6.0kGy的辐射剂量对番茄红素影响不大。