上海地区胃癌病人运铁蛋白(Tf)、组特异性成分(Gc)、α_1-抗胰蛋白酶(α_1-AT)亚型分布的研究

用薄层聚丙烯酰胺凝胶等电聚焦电泳分析了上海地区202例汉族胃癌病人及202例正常对照组的运铁聋白(Tf)和α_1-抗胰蛋白酶(α_1-AT)亚型的分布,发现胃癌组Tfc_1c_1纯合子频率(0.3713)和Tfc_1基因频率(0.5718)显著低于对照组(分别为0.5149和0.6782),均为p<0.01,胃癌组Tfc_2c_2纯合子频率(0.2228)和Tfc_2基因频率(0.4019)显著高于对照组(分别为0.1436,p<0.05和0.2970,p<0.01),胃癌组和对照组的α_1-抗胰蛋白酶亚型分布无显著差异。用薄层聚丙烯酰胺等电聚焦结合免疫固定分析了上海地区200例汉族胃癌病人和200例正常对照组的组特异性成分(Gc)亚型分布,发现胃癌组Go1F表型频率(0.22)和Gc1F基因频率(0.4375)均显著高于正常对照组(分别为0.14和0.3600,均为p<0.05)。     

Detection of covalent enzyme-substrate complexes of nitrilase by ion-spray mass spectroscopy

Nitrilase from Rhodococcus ATCC 39484 was found to consist of two species of Mr 40,258 +/- 2 and 40,388 +/- 2 Da. When the enzyme was incubated with nitrile substrates and the reaction quenched with acid, higher Mr species were observed. The mass differences were consistent with addition of a substrate molecule to each species. These results represent the first reported demonstration that this, or any other nitrilase forms a covalent intermediate with its substrates. The observation that the intermediate, suggested to be either a thioimidate or an acylenzyme, can be trapped by acidification indicates that the rate of breakdown of the intermediate is rate-limiting.     

Vibrational fluctuations of hydrogen bonds in a DNA double helix with nonuniform base pairs.

The Green's function technique is applied to a study of breathing modes in a DNA double helix which contains a region of different base pairs from the rest of the double helix. The calculation is performed on a G-C helix in the B conformation with four consecutive base pairs replaced by A-T. The average stretch in hydrogen bonds is found amplified around the A-T base pair region compared with that of poly(dG)-poly(dC). This is likely related to the A-T regions lower stability against hydrogen bond melting. The A-T region may be considered to be the initiation site for melting in such a helix.     

A method for separating bound versus unbound label during radioiodination

An inexpensive, highly effective, and safe method for the removal of bound versus unbound label during radiolabeling of proteins is described. The technique employs the use of membrane ultrafiltration technology and returns in one step a highly reproducible product of quality superior to that attained by gel chromatography. Advantages of this technique are a reduction in the quantity of liquid and solid radioactive waste and a significant limitation of potentially harmful manipulation and exposure times.     

Pyrophosphate contamination in crystalline phosphocreatine: a source of error in kinetic studies using coupled enzymes.

Commercial crystalline phosphocreatine generally contains a contaminant, probably pyrophosphate, that can inhibit nucleoside triphosphatases and may therefore cause errors in steady-state kinetic studies of creatine kinase-coupled r reactions. Ion-exchange chromatography reveals the presence of pyrophosphate in some batches of phosphocreatine sufficient to account for the observed inhibition. Chromatographically purified phosphocreatine shows no inhibitory effect.     

Sound localization behavior of the green treefrog (Hyla cinerea) and the barking treefrog (H. gratiosa)

Summary Female treefrogs (Hyla cinerea andH. gratiosa) can accurately localize a sound source (playback of male mating calls) if both ears are intact. When the sensitivity of one eardrum is attenuated, by coating it with a thin layer of silicone grease, females no longer can locate the sound source. This study demonstrates that female anurans rely on interaural cues for localization of a calling male. The neural basis for an anuran's sound localization ability presumably involves binaural convergence on single cells in the central auditory nervous system.This work was supported by research grants from the National Science Foundation and the U.S. Public Health Service. The assistance of Anne J.M. Moffat in measuring the directional characteristics of the loudspeaker is gratefully appreciated.     

用EDTA法研究镰刀菌胞内、胞外Pb2+的分布特征

【目的】建立一种方便、快捷、相对准确、能够定量地测定镰刀菌细胞内、外Pb2+分布的技术手段。【方法】用EDTA溶液浸泡镰刀菌细胞,使其胞外(表面)Pb2+被螯合、洗脱并测定,之后将被浸泡、清洗过的细胞消解、测铅。【结果】EDTA可以将镰刀菌表面的Pb2+螯合,且在99 min内不损伤镰刀菌细胞;以EDTA为反应介质和滴定剂,XO为指示剂,测定镰刀菌胞内、胞外Pb2+分布是可行的。依据此实验方法,测定了镰刀菌在Pb2+浓度为500 mg/L的培养基中的生长曲线、培养基中Pb2+浓度和细胞内、外Pb2+的含量。【结论】镰刀菌固定Pb2+的过程是先将Pb2+吸附在菌体胞外,之后转运至细胞内部,菌体胞外Pb2+的容纳量是有限的,每克菌体胞外Pb2+饱和吸附量约1.37 mg,通过计算可得,每克菌体用于吸附Pb2+的胞外活性位点约3.97×1018个。     

基于Agent模型的生态公平指数构建与模拟

伴随着社会经济的发展,社会公平逐渐成为热点话题。社会公平问题不但体现在社会现象上,还对生态系统起着重要的影响。通过构建资本交换自主体模型,模拟社会财富分配动态过程,可观测资本交换熵指数变化情况,从而解释熵增原理。除此以外,不同系统的最终状态能达到的最大熵指数不同,用熵增原理与本文构建的最大熵指数模型可以对系统的生态公平进行纵向或横向评价。构建的资本交换熵模型也可以证明最大熵原理,同时,财富集中的现象将会使生态环境的选择权完全交予富人群体,影响可持续发展。     

不同坡向高寒草甸土壤理化特性和微生物数量特征

阐明不同坡向草地土壤性质的空间分异格局,为退化草地的精准修复和科学管理提供参考。研究了青藏高原东缘高寒草甸退化草地不同坡向(北坡N、西北坡NW、西坡W、东坡E、东北坡NE、西南坡SW和南坡S)土壤理化性质和微生物数量特征。结果发现:从N→S坡向上,土壤有机质、碳氮比和全氮含量均呈下降趋势,土壤全磷含量和pH值在不同坡向间均无显著差异(P0.05),E坡向全磷含量最高((2.83±0.95)g/kg),NW坡向含量最低((2.07±0.12)g/kg);土壤细菌、真菌和放线菌数量变化呈波动现象,NW坡向的细菌((13.0×10~5±1.0×10~5)个/g)、真菌((14.0×10~3±0.0)个/g)和放线菌((24.0×10~4±1.0×10~4)个/g)数量最低,E坡向的细菌数量最高((85.5×10~5±2.5×10~5)个/g),S坡向的真菌((24.0×10~3±0.0)个/g)和放线菌((209.5×10~4±4.5×10~4)个/g)数量最高;回归分析表明,在E→S坡向上,随土壤含水量、有机质、碳氮比和全氮含量的增加,土壤细菌和放线菌数量均显著降低(P0.05),而土壤真菌数量随含水量、pH值、土壤养分含量的增加略有降低(P0.05)。可见,不同坡向高寒草甸土壤理化特征差异明显,也导致了土壤微生物数量分配格局的不同。