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关键词： cytochrome P450   cytochrome b(5)   P450 reductase   conformational dynamics  

摘要： Dissociation constants K-d for cytochrome P450 reductase (reductase) and cytochrome P450 2134 are measured in the presence of various substrates. Aminopyrine increases the dissociation constant for binding of the two proteins. Furthermore, cytochrome b(5) (b(5)) stimulates metabolism of this substrate and dramatically decreases the substrate-related K, values. Experiments are performed to test if the b(5)-mediated stimulation is effected through a conformational change of P450. The effects of a redox-inactive analogue of b(5) (Mn b(5)) on product formation and reaction stoichiometry are determined. Variations in the concentration of Mn b5 stock solution that have been shown to effect the aggregation state of the protein alter the rate of P450-mediated NADPH oxidation but have no effect on the rate of product formation. Thus, the electron transfer capability of b(5) is necessary for stimulation of metabolism. Furthermore, stopped flow spectrometry measurements of the rate of first electron reduction of the P450 by reductase indicate that the coupling of P450 2B4-mediated metabolism improves, in the presence of Mn b(5), with slower delivery of the first electron of the catalytic cycle by the reductase. These results are consistent with a model involving the regulation of the P450 catalytic cycle by conformational changes of the P450 enzyme. We propose that the conformational change(s) necessary for progression of the catalytic cycle is inhibited when reduced, but not oxidized, reductase is bound to the P450. (C) 2003 Elsevier Inc. All rights reserved.

关键词： nicotinic acetylcholine receptor (nAChR)   acetylcholinesterase inhibitor (AChE-I)   allosterically potentiating ligand (APL)   galanthamine   tritium  

摘要： A new promising galanthamine derivative, 10-[H-3]methylgalanthamine iodide, was synthesized for binding studies to nicotinic acetylcholine receptors expressed in Torpedo electric ray electroplaques. Galanthamine was reacted with [H-3]methyl iodide to yield 10-[H-3]methylgalanthamine iodide with a radiochemical yield of > 70% and a specific activity of 32 Ci/mmol after purification via solid phase extraction. To test the ligand properties of the radioligand, calcium imaging and electrophysiology of the non-radioactive analogue were performed to obtain an EC50 of 270 nM, a Hill coefficient of 1.9 nd the induced cell current. Copyright (C) 2003 John Wiley Sons, Ltd.

关键词： 文件检验   文字书写压痕   复写纸   形成时间  

摘要： 文字书写压痕亦称抑压文字或压痕字迹,是指书写活动过程中,由于书写运动力的作用,在承受客体下面衬垫的纸张上遗留的无色凹陷字迹、笔画痕迹.

关键词： 形式   功能   登记   证据效力  

摘要： 合同对于形式的要求在当代已渐趋衰微 ,但是形式本身存在的功能又使得立法者不能对其完全抛弃。合同形式在当代社会仍具有独特的功能、价值、种类和效力。

关键词： 供电企业   供用电秩序   违约   侵权   转供电纠纷性质   法律   债权  

摘要： 近日,安徽省某供电局将一起纠纷上报省电力公司,并咨询处理的方式和手段。其基本案情如下:某工厂地处远郊,供电部门难以把其纳入供电区域,当时只好由该厂代为转供。现由于经济的快速发展,城市的进一步扩张,该地区的用电量猛增,已大大超过了该厂的供电能力。

关键词： 巴拉萨—萨缪尔森效应   误差修正模型   第三产业工资水平   实际汇率决定  

摘要： 　对实际汇率的实证前期研究一直集中在贸易部门,本研究开始将实证的领域拓展到非贸易部门(即使用非贸易部门工资作为比较变量)。运用了误差修正模型来验证第三产业的工资变化与实际汇率之间存在着协整关系。这种协整关系在人民币、日元的检验上得到了支持。随着第三产业占各国GDP的比重越来越大(发达国家在68%～84%之间),该部门对实际汇率的影响举足轻重。实证结果表明,中国的实际汇率的平稳与中国的第三产业工资变化起伏较小相关。日元实际汇率上浮与日本的第三产业的工资提高成正比。从而验证了巴拉萨—萨缪尔森效应在中日实际汇率决定中是存在的。但是否在其他亚洲国家实际汇率决定中也同样存在则需要进一步证明。

关键词： 检疫   毒理检验   食品添加剂   化妆品   安全性检验  

摘要： 毒理检验对保证食物、化妆品和化学产品安全具有重要作用。从在检验检疫中开展毒理检验的主要法规依据、检验检疫系统毒理检验现状和检验检疫需要开展毒理试验工作三个方面探讨了毒理学在检验检疫工作中的地位、作用和意义。介绍了检验检疫系统目前的毒理检测能力、主要工作对象和工作量。提出了检验检疫开展毒理试验的工作重点是在研究、认识和发现食品添加剂和新型食品原料成分的安全性 ,食品生产加工中产生的危害物的毒性。同时 ,在化妆品和其他化工产品的安全性检验中也能发挥重要作用。

关键词： 中国   劳动力市场   劳动生产率   人力资本理论   筛选理   教育收益率   受教育程度  

摘要： 在中国特定的文化以及制度环境中,教育的个人收益率所反映的教育与收入的关系究竟来自社会对教育的信号作用的认同,还是代表了教育确实对提高劳动生产率产生的贡献?教育的生产性功能和筛选功能究竟是在多大程度上发挥作用的?随着市场经济的不断完善,教育的生产性功能与信息性功能是否会有变化?变化的趋势又如何?本文通过将中国劳动力市场中不同部门、不同地域的教育收益率进行对比,评估中国劳动力市场中教育的生产促进和筛选作用。同时通过对比不同时点进入劳动力市场的劳动者的教育收益率,验证教育的信息性功能与生产性功能变化的趋势,并从侧面检验中国劳动力市场的市场化进程。

关键词： yaws   Pacific Islands   palaeopathology   limb deformity  

摘要： Clinical reports from tropical countries show that the tertiary lesions of yaws (Treponema pertenue) can cause gross deformities of cutaneous and osseous tissues representing a functional cost to the individual and the community. The palaeopathological literature rarely considers the cost of bone lesions to the individual in terms of limitations in limb function. This paper presents 14 cases with joint and bone lesions in a skeletal sample from prehistoric Taumako Island, southeast Solomon Islands, Southwest Pacific Islands. Clinical reports describing these types of lesions are reviewed in an attempt to assess the functional consequences of joint pathology. A differential diagnosis includes tuberculosis, leprosy and rheumatoid arthritis;however all those affected had co-existent lesions indicative of treponematosis which favours a diagnosis of yaws. The possibility of a concurrent condition contributing to the development of these lesions is not ruled out. The possible pathogenesis of the lesions and related disability is also addressed. (C) 2003 Elsevier Ltd. All rights reserved.

关键词： multicategory classification   on-line learning algorithm   pattern recognition   structural risk minimization   stochastic gradient descent learning  

摘要： Consider the pattern recognition problem of learning multicategory classification from a labeled sample, for instance, the problem of learning character recognition where a category corresponds to an alphanumeric letter. The classical theory of pattern recognition assumes labeled examples appear according to the unknown underlying pattern-class conditional probability distributions where the pattern classes are picked randomly according to their a priori probabilities. In this paper we pose the following question: Can the learning accuracy be improved if labeled examples are independently randomly drawn according to the underlying class conditional probability distributions but the pattern classes are chosen not necessarily according to their a priori probabilities? We answer this in the affirmative by showing that there exists a tuning of the sub-sample proportions which minimizes a loss criterion. The tuning is relative to the intrinsic complexity of the Bayes-classifier. As this complexity depends on the underlying probability distributions which are assumed to be unknown, we provide an algorithm which learns the proportions in an on-line manner utilizing sample querying which asymptotically minimizes the criterion. In practice, this algorithm may be used to boost the performance of existing learning classification algorithms by apportioning better sub-sample proportions. (C) 2003 Elsevier Science (USA). All rights reserved.