A novel algesic peptide derived from skin secretions of the frog Amolops loloensis

Several algesic agents including bradykinin and tachykinin have been identified from skin secretions of amphibians. They may act in defensive roles against aggressors. In this study, a novel peptide named Amolos with an amino acid sequence of FLPIVGAKL an

Calcium-permeable acid-sensing ion channel is a molecular target of the neurotoxic metal ion lead

Acid-sensing ion channels (ASICs) are emerging as fundamental players in the regulation of neural plasticity and in pathological conditions. Here we showed that lead (Pb2+), a well known neurotoxic metal ion, reversibly and concentration-dependently inhib

Cage culture of sea bass in Malaysia

The article discusses the cage culture practice of sea bass (Lates calcarifer) in Malaysia. Problems on feed and seed supply and overcrowding are also discussed. Despite these problems, seabass cage culture still continuously booms.

尖吻蝮蛇凝血酶进入国家一类新药临床实验阶段

由中国科学院昆明动物研究所肖昌华研究员主持的“注射用尖吻蝮蛇凝血酶”研究项目, 经国家药品监督管理局审查, 符合国家一类新药审批的有关条件, 批准于2003年4月进入Ⅰ期临床实验 (批件号: 2003L01430). 尖吻蝮蛇凝血酶为我国特产的尖吻蝮(Agkistrodon acutus) 蛇毒中分离纯化的蛇毒凝血酶(Hemocoagulase, 止血酵素), 其生理作用与从矛头蝮 (Bothrope jararoca)蛇毒中得到的蛇毒凝血酶 (Hemocoagnalse, Reptilase. Batroxobin)相似, 但化学结构则完全不同, 是一种新型结构的蛇毒止血酶, 属一类生化药品制剂。

Hybrid deterministic-statistical modelling of built-up structures

When used correctly, Statistical Energy Analysis (SEA) can provide good predictions of high frequency vibration levels in built-up structures. Unfortunately, the assumptions that underlie SEA break down as the frequency of excitation is reduced, and the method does not yield accurate predictions at "medium" frequencies (and neither does the Finite Element Method, which is limited to low frequencies). A basic problem is that parts of the system have a short wavelength of deformation and meet the requirements of SEA, while other parts of the system do not - this is often referred to as the "mid-frequency" problem, and there is a broad class of mid-frequency vibration problems that are of great concern to industry. In this paper, a coupled deterministic-statistical approach referred to as the Hybrid Method (Shorter & Langley, 2004) is briefly described, and some results that demonstrate how the method overcomes the aforementioned difficulties are presented.

New type of multimode-interference-type thermo-optic variable optical attenuator

A thermo-optic variable optical attenuator (VOA) based on a Mach-Zehnder interferometer and multimode-interference coupler is fabricated. Not a single-mode but a multimode waveguide is used as the input and output structures of the optical field, which greatly reduces the coupling loss of the VOA with a normal single-mode fiber. The insertion loss of the fabricated VOA is 2.52 to 2.82 dB at the wavelength of 1520 to 1570 nm. The polarization dependent loss is 0.28 to 0.45 dB at the same wavelength range. Its maximum attenuation range is up to 26.3 dB when its power consumption is 369 mW. The response frequency of the fabricated VOA is about 10 kHz. (C) 2004 Society of Photo-Optical Instrumentation Engineers.

科尔沁沙地东南部固沙林土壤磷素研究

土壤养分的持续供应是生态系统可持续性发展的基础，尤其在土壤贫瘠地区。土壤磷素被认为是干旱区生态系统的潜在限制性养分因子，但目前半干旱区土壤磷素的深入研究很少。针对半干旱区生态系统恢复方式、人工防护林可持续性经营等关键问题，本论文旨在弄清处于半干旱区的科尔沁沙地东南部沙地人工林土壤磷素转化的主导过程及影响因素，并从土壤磷素可持续供应的角度来评价研究区生态系统的可持续发展。 以处于无人为干扰下、立地条件基本一致的科尔沁沙地东南部的有代表性的生态系统为研究对象，包括原生植被榆树（Ulmus macrocarpa）疏林草地，退化草地，油松（Pinus tubulaeformis Carr.）人工林、樟子松（Pinus svlvestris var. mongolica）人工林和小叶杨（Populus simonii）人工林。系统全面的研究了土壤磷素状况及其季节变化，并深入探讨了樟子松人工林土壤磷素转化及其影响因素（林龄、密度、土壤冻融）。主要结论如下： （1）研究区风沙土表层0~20 cm全磷（<0.2 g kg-1）和活性无机磷含量（<3 mg kg-1）都极低，有机磷占全磷的50%以上，是土壤磷的主要组分。凋落物分解、有机磷矿化和微生物周转是有效磷的主要来源，与这些过程有关的土壤的生物过程控制着土壤磷素转化。Ca-P（钙结合的磷酸盐）的溶解也是速效磷的次要来源，而Al-P（铝结合的磷酸盐）和Fe-P（铁结合的磷酸盐）是活性无机磷库。凋落物分解对有效磷供应起首要作用（尤其在人工林中），凋落物分解的年磷归还量是10 cm层矿质土壤有效磷供应量的1.7~3.4倍。 （2）土壤含水量是影响土壤磷素供应的关键环境因子，而冻融作用对土壤微生物磷和活性无机磷含量无显著影响。 （3）与各人工林相比，榆树疏林草地具有高效的养分循环和较强的土壤磷素保持能力，其退化大幅度降低了土壤持水能力和肥力。而在退化草地上营造以针叶树种为主的人工纯林及针阔混交林进一步降低了土壤全磷含量。从土壤磷素可持续供应的角度来看，在干旱贫瘠地区不宜营造高密度的人工林。研究区的植被恢复，应该选取磷素利用效率高，而养分周转较快的植被类型。这样，不需要集中的人为管理，就能使生态系统达到一种自我维持的良性循环状态。 （4）樟子松的生长受到土壤磷素供应的限制，当年生叶片无机磷浓度比全磷浓度能更准确、直接地反映土壤供磷水平的变化。为满足林分的需求，樟子松的根系活动能够增强根际微生物和磷酸酶活性以促进有机磷的矿化，同时能降低根际土壤pH值以促进Ca-P的溶解。随着林分的发展，活性无机磷含量无显著变化，但土壤磷库（主要是总有机磷）逐渐耗竭，有机磷的矿化潜力也逐渐降低。这表明，随着林分发展，磷素对樟子松人工林的限制性逐渐增强。 （5）为保证已有人工林的可持续发展，必须通过间伐、保护地被物、施肥来调节养分需求与归还之间的平衡，维持地力，保证土壤养分的持续供应。其中保护林下凋落物尤为重要。为防止地力衰退，该地区樟子松林的最大密度（以每公顷胸高断面积为密度指标）应保持在24.1~26.6 m2 ha-1。

固定化红酵母细胞合成L-苯丙氨酸研究

In this paper, bioconversion of trans-cinnamic acid(t-Ca)to L-phenylalanine (L-phe) has been investigated by using immobilized yeast cells with induced L-phe Ammonia-lyase(PAL, EC.4.3.1.5) as biocatalysts. The contents are the following. (1) Thirty strains of yeasts, including two genera (Rhodotorula, Sporobolomyces), six species (R. glutinis R. minuta,R.rubra,R.sineses,R.roseus and S.salmonicolor)were screened for their ability to converse the substrates, t-Ca and ammonia, to the product, L-phe, by using yeast cells as biocatalyst, and primary evaluation for PAL activity of the selected strains was investigated. From the results of the screening experiments, it was found that 22 strains were able to produce L-phe from t-Ca with the range of conversion yield from 2% to 67%. Studies on PAL formation time course during cultivation show that the maximum PAL activity of several different strains ranges from 2.3 to 14.4×10-3U/mg cell dry weight. The biomass of tested strains at their maximum enzyme activity is also greatly varied. (2)One of the selected strains, R. rubra as 2.166, was used for immobilized cells as biocatalysts to produce L-phe. The optimum conversion conditions and effective stablization agents were investigated. The results shown that polyacrylamide gel was chosen as a suitable matrix for immobilization of the yeast cells, and it can retain 88% of the PAL activity in the reverse direction at the following reactive conditions: [t-Ca]: 34mM. [NH4OH]: 6.OM.PH10.00, temperature: 30℃. (3) The effects of various kinds of effectors on the production of L-phe were also examined. Membrane permeabilizing agents can stimulate L-phe synthesis, but make the stability of PAL decline greatly. Polyalchoholic agents and glutamic acid were very effective for the stabilization of PAL. At the presence of glutamic acid (5%), the half life of L-phe productivity with the immobilized cells was extended to 192 hours, which was much higher than most of that having been reproted, while the half life of resting cells was only about 15 hours. (4) Use of initial velocity studies on the kinetics of enzyme-catalized reaction indicated that the apparent Km value was 13.0mM for the immobilized cells, and 4.8mM for the resting cells. Thermostability of the immobilized cells was better than the resting cells. Fluid bed bioreactor is more effective than batch bioreator in prolonging the thermostability of the biocatalysts. (5) CGA- 688 resin column chromatographic procedure was employed in the isolation and purification of L-phe, t-Ca and other substances from the reactire mixture. (6) Preparative-scale production of L-phe on a level of gram amount by immobilized cells from the culture broth of R. rubra AS2.166 allowed for the conversion yield with 30%. The characteristic physico-chemical criteria (including melting point, optical activity, elements analysis, IR, NMR) are the same with the standard L-phe. 本文报告了利用诱导的苯丙氨酸解氨酶 (PAL.EC.4.3.1.5)催化反式肉桂酸(t-Ca)氨加 成制备L-苯丙氨酸(L-phe)的研究，主要内容为：(1) 我们搜集了三十株酵母菌株，利用全细胞转化t-Ca生成L-phe的能力进行了直 接筛选，并对其PAL活性水平进行了初步评估研究。研究结果表明，其中22株酵母具有转化t-Ca生产L-phe的能力，它们包括 Rhodotorula glutinis,R.rubra, R.sineses 和Sporobolomyces roseus 的菌株，转化率在2-67%。细胞生长和PAL形成过程的研究 表明，不同菌株PAL最大活力在2.3-14.4×10-3U/mg 细胞干重，达到最大PAL活性时各株酵母的生长情况也极不一致。(2) 利用筛 选出的一株深红酵母R.rubra AS2.166 作为供试菌株，研究了细胞固定化条件下生物转化的最适条件及PAL在固定化条件下的稳定 性。结果表明以聚丙烯酰胺凝胶包埋法较为理想，能使细胞合成L-phe活力保持88%，最适t-Ca浓度为34mM，最适NH4OH浓度为6M,最 适PH10.0，最适温度45℃。(3) 多种效应物对L-phe 合成的影响研究表明：表面活性剂能刺激L-phe的合成，但使PAL稳定性下降。 多羟基化合物及Glu对PAL的稳定十分有效在有Glu存在下，能使固定化细胞合成L-phe的半寿期达192小时左右，高于大部分现已报 导的固定化结果。(4) 用初速度法研究了深红酵母AS2.166中PAL的酶促反应特征，测得固定化细胞对t-Ca的表观米氏常数Km为 13.0mM，全细胞为4.8mM，细胞固定后热稳定性提高。(5) 建立了适合低浓度分离纯化产物与底物的聚苯乙烯大孔树脂柱层析技术 ，能使L-phe与t-Ca及产物混合物中其它成分有效分开。(6) 利用固定化的R.rubra AS2.166细胞所做的制备实验能够使L-phe的产 率达到30%左右，其主要的理化指标(包括熔点、比旋光度、元素分析、IR、NMR等)与标准L-phe一致。

用中子晕弹核探寻同位旋非对称核物质状态方程

总结和评述了用中子晕弹核探寻同位旋非对称核物质状态方程。在具有同位旋和动量依赖的同位旋相关量子分子动力学框架内,采用对比中子晕弹核和相等质量稳定弹核在完全相同入射道条件下物理观测量的差别,来突出中子晕核明显的同位旋效应和加强物理观测量对于同位旋的灵敏性,从而提取核物质状态方程。例如,与稳定弹核碰撞系统相比,中子晕弹核明显提高了发射核子的中子-质子比和增加了它对于对称势的灵敏性,这两点特征非常有利于提取对称势。同样,由于中子晕弹核碰撞系统在低能区(E<60MeV)由于内部松散结构减弱了核子碰撞力度和动量耗散,与稳定核碰撞系统相比,明显提高了原子核阻止;而在高能区由于两体碰撞同位旋效应的增加,从而明显提高了原子核阻止。利用这些特征可以提取核子-核子碰撞截面的介质效应和同位旋依赖性。

中国2kaBP前后的气候及其影响

根据近20年来由历史文献、冰心、孢粉、湖泊沉积等多种代用资料恢复的历史时期气候变化状况,对中国2kaBP前后的气候变化及其可能影响以及驱动机制进行了综合推断,结果表明:2kaBP前后,中国的气候发生了明显的变化,在温度变化方面,新疆地区由寒冷转为温暖,其余地区由温暖转为寒冷;在降水变化上,北方大部分地区降水量下降,干旱化趋势明显,南方地区降水量变化不大,仍然比较丰富。此期,自然灾害增多,农业生产范围缩小,人口数量减少,政局不稳定,甚至出现政权更迭等社会不稳定事件。太阳活动、大气环流和火山活动可能是引起此次

Ring-Opening/Recyclization Reactions of (Dimethylamino)propenoyl-Substituted Cyclopropanes: Facile Synthesis of Halogenated Pyridin-2(1H)-ones

A facile and efficient synthesis Of Substituted pyridin-2(1H)-ones has been developed by the reaction of readily available 1-carbamoyl-]-[3-(dimethylamino)propenoyl]cyclopropanes with phosphoryl chloride or phosphorus tribromide in dichloromethane at room temperature.

富含a-亚麻酸的多烯磷脂酰胆碱及其生产方法

一种富含ａ－亚麻酸的多烯磷脂酰胆碱的脂肪酸组成中含２０－４０ｗｔ％ａ－亚麻酸，其酸值５－４０ｍｇＫＯＨ／ｇ，碘值８０－１３０ｇＩ↓［２］／１００ｇ，磷含量２．７－３．８％。其生产方法是以高纯度蛋黄卵磷脂为原料，与富含ａ－亚麻酸油脂混合，通过生物酶催化酯交换，生成富含ａ－亚麻酸的多烯磷脂酰胆碱，本发明具有多烯脂肪酸为ａ－亚麻酸、酯交换反应容易、发挥多不饱和脂肪酸和磷脂的双重作用、反应体系无溶剂、磷脂型ａ－亚麻酸更稳定、通过超临界萃取分离反应产物解决了分离难题等优点。