蛋白质溶液可逆热变性及其与肽链构象关系的研究

用微量扫描量热技术及远紫外圆二色谱研究了蛋白质水溶液的浓度和ｐＨ对蛋白质热变性可逆性的影响及其与在热变性时肽链构象的关系。结果表明,当蛋白质溶液的浓度为０．０４％、ｐＨ为３时可实现完全可逆的热变性,然而蛋白质溶液宏观上的热变性并不意味着微观上蛋白质分子肽链的完全伸展。     

抗疟药物氯奎、阿的平、四氢-9-氨基(口了)啶与双链小牛胸腺DNA的结合

本文用体相微量量热计所得数据,估算了两种抗疟药物(antimalarial)分子和两种结构上相似的分子与DNA结合时的标准结合热焓。根据在不同离子强度下测定的表观结合常数获得了热力学结合常数。根据这些数据以及标准结合热焓计算出标准结合自由能、标准结合熵。结果发现凡与DNA结合的分子,具有线性芳环结构的,结合时主要取决于热焓的大小。具有脂肪链或脂肪环结构的,结合时主要取决于熵变。     

微量热泳动技术的生物医学研究进展

微量热泳动技术基于荧光标记分子在温度梯度内的定向移动,能够在溶液中快速、灵敏地测量生物相关分子间的相互作用。它不需要表面固定和大量样品,对相对分子质量也没有限制。热泳动对分子的大小、电荷和水化层的微小变化都十分敏感,适合于蛋白质、核酸、小分子和离子等多种物质的相互作用研究。微量热泳动技术由于其独特的优势,目前已经在生物医学领域中有了初步应用。本文介绍了微量热泳动技术的背景和其在生物医学领域中不同生物相关分子间相互作用分析的研究进展。     

不同灌溉方式下3种土壤微生物活性测定方法比较

探究不同灌溉方式下土壤微生物活性,对维持土壤稳定和提高水资源利用效率具有重要意义。以沈阳农业大学长期定位灌溉试验基地为平台,采用土壤酶活性、土壤呼吸和微量热法,研究节水灌溉组覆膜滴灌、渗灌及对照组沟灌下的土壤微生物活性并比较3种微生物活性测定方法。结果表明:不同灌溉方式下土壤脲酶、转化酶、脱氢酶活性无显著差异,土壤呼吸在3个主要生长季也没有明显变化规律;而微量热法得到的热功率时间曲线呈现了典型的微生物生长特征趋势,覆膜滴灌的生长速率较大,且与沟灌的总热量、最大热功率相差不大。因此,从可持续农业观点出发,覆膜滴灌是保证土壤微生物活性较高的一种节水灌溉方式;微量热法也为传统方法下不易检测的微生物活性提供了新思路。     

光谱和微量热法分析柑橘苷与BSA分子间作用及构建其理论模型

光谱和微量热法分析柑橘苷(naringin,NAR)与牛血清白蛋白（bovine serum albumin, BSA）分子间作用,构建NAR与BSA分子间作用的理论模型。采用紫外-荧光光谱法解析Fōrster方程求得NAR与BSA分子间作用及分子间作用的临界距离r,等温滴定微量热技术测定NAR与BSA分子间作用的积分量热曲线,获得Δ H并通过Gibbs-Helmholtz方程获取Δ S和Δ G。基于光谱和微量热辅助分析,构建NAR与BSA分子间作用的理论模型。结果表明,光谱法测出NAR与BSA发生分子间作用,NAR与BSA分子间作用的临界距离为2.06 nm,表明NAR与BSA分子间作用为短程分子间作用。微量热法成功测定出NAR与BSA分子间的热力学参数Δ H<0,Δ S>0,Δ G<0,说明NAR与BSA分子间作用是自发进行的放热相互作用。依据Ross理论分析NAR与BSA分子间作用力主要是疏水作用力和静电作用力。模型构建结果说明,NAR与BSA分子间作用主要发生在BSA的domain IIA区域,NAR与BSA分子间作用力主要是静电作用力,兼有范德华作用力和氢键。实验与理论模型构建结果基本一致。本研究工作可为深入了解蛋白质与大分子化合物间的作用以及研究微观药理学机制提供有益的参考。     

限制性条件下药物对细菌抑制作用微量量热法研究

用微量量热计测定了福氏志贺氏菌(Shipella flexneri)中7株菌(6、2b、3b、sb、la、x、y)在合成药物抑制作用下生长的热谱图,按限制性条件下微生物生长的模型进行了数学处理,得出了比生长速率(μ),由此确定了各细菌比生长速率(μ)与药物浓度?之间的定量关系,求出了比生长速率(μ)为零时的用药浓度,并对该合成药对各细菌的抑菌效果进行了分析．     

微量热法研究磁性生物材料与大肠杆菌的相互作用

目的:考察利用微量热法研究磁性生物材料与大肠杆菌相互作用的优势.方法:将大肠杆菌与磁性生物材料共同培养,利用微量热仪记录大肠杆菌的生长放热曲线,分析拟合获得大肠杆菌生长过程的热动力学参数.然后观察大肠杆菌的显微形态,并分析其形态变化.同时利用光电比浊法测定大肠杆菌的密度.结果:磁性生物材料导致大肠杆菌的生长速率常数降低,茵液最大放热功率下降,生长代谢受到抑制.而电镜观察发现,与磁性生物材料共同培养的大肠杆菌菌体萎缩变形,细胞壁出现褶皱和破损.与光电比浊法的研究结果相比,微量热法的研究结果能更符合电镜观察结果.结论:磁性生物材料破坏了大肠杆菌的细胞壁,导致大肠杆菌生长代谢受到抑制.此外,微量热法有助于研究磁性生物材料与细菌的相互作用.     

绿量的城市热环境效应研究现状与展望

绿量对城市热环境的调控功能已成为目前研究热点。本文从绿量的概念与发展、绿量与城市热环境的调查方法、绿量与城市热环境的关联性以及其在城市规划方面的启示4方面进行论述,总结国内外研究进展,提出了未来该领域的4个发展方向,包括三维绿量调查方法的改善、城市热环境的监测与预测、城市绿量三维空间格局指标体系的构建以及关联绿量与城市热环境研究的三维空间格局分析方法的创建。本文为研究绿量调控城市热环境提供了一种三维空间分析的视角,以期更深入地探索城市绿量的三维空间格局、平衡城市热环境的适宜性和多方面生态效益,为城市绿色空间规划与设计提供科学依据,也为人类适应气候变化并科学调控城市热环境提供理论支持。     

应用引物延伸预扩增提高微量DNA拷贝数

采用引物延伸预扩增方法 ,可普遍提高微量模板DNA的拷贝数 ,便于进行基因分析时克服标本量少、来源困难的制约。采用常规扩增、检测 2 4 8bp的DYZ1片段体系为观察对象 ,其最小模板量需 1.5ng/2 0 μl体系。以 15个碱基随机寡核苷酸为引物 ,对最小模板量进行预扩增 ,再以其产物 1/10为模板 ,特异扩增DYZ1片段。进行相对定量分析 ,判断原模板DNA拷贝数增加的程度。结果 1.5ng男性DNA经随机扩增后 ,此DYZ1片段拷贝数增加了 10倍以上 ,大大地提高了特异DNA片段扩增的模板量。表明经随机引物延伸预扩增后 ,微量标本DNA片段拷贝数获得普遍提高 ,增加了微量DNA扩增的敏感度     

应用微量热法构建限制性条件下微生物生长模型

用微量热计测定了金黄色和白色葡萄球菌在给定条件下生长的热谱图,按限制性条件下微生物生长的模型进行了数学处理,得出了比生长速率．还测定了在不同温度和不同酸度下的热谱曲线,确定了最适生长温度和酸度。     

口蹄疫病毒感染BHK—21细胞的代谢热谱研究

本文应用高灵敏度的LKB2277生物活性检测仪测定FMDV感染BHK-21细胞的代谢热谱,并与传统方法测定的一步生长曲线进行比较,二者具有显著的相似性。结果表明,微量热法通过对细胞及其受病毒感染的细胞体系代谢热的测定,能有效地监测病毒在宿主细胞内增殖的过程。该方法还提供了一种动态连续分析病毒感染增殖的新手段。     

Comparison of an iterative microcalorimetric method and dialysis equilibrium for calculating thermodynamic parameters of a binding protein which presents a weak affinity for its substrate

An original iterative microcalorimetric method is used to study the interaction of 5-fluorouracil, a cancer chemotherapeutic agent, with human serum albumin. Two equivalent binding sites are demonstrated with an association constant and an enthalpy variation equal to 370 ± 30 m^?1 and ?10 ± 0,5 kcal/mol, respectively. By means of a competitive microcalorimetric method, the partially competitive binding of dipotassium chlorazepate and 5-fluorouracil is shown. This iterative microcalorimetric method can be applied to all techniques involving the measurement of a phenomenon which is proportional to the concentration of the complex.     

Analysis of microcalorimetric curves for bacterial identification

A numeric method is suggested for the treatment of microcalorimetric curves of bacterial growth to provide a new tool for their automatic identification. In this method the microcalorimetric curves are searched against certain reference profiles (stored in a library) by means of a cross-correlation analysis and a parametric comparison. The matching between the new curve and each reference profile is evaluated by means of a specific identification coefficient which provides an objective criterion for the identification of each species. The reliability of the method is discussed.     

Flow Microcalorimetric Studies of Yeast Growth: Fundamental Aspects

The importance of factors such as cultural conditions e.g. organism background, inoculum density and glucose concentration are explored and their effects on the experimental recording discussed. The relevance of these findings to microbial microcalorimetry in general and to microcalorimetric identification of organisms in particular is described. The conclusions drawn are (i) that microbial identification by microcalorimetry is not possible and (ii) that great caution must be exercised in interpreting metabolic data derived from microcalorimetric studies.     

Microcalorimetry is a sensitive method for studying the effect of nucleotide mutation on promoter activity

Microcalorimetric method was successfully used to study the effect of nucleotide mutations on promoter activity and identify the important nucleotide necessary for the promoter function in Escherichia coli. The thermokinetic parameters, such as k, I and IC(50), were calculated from the metabolic power-time curves obtained by microcalorimetric measurement using the TAM air Isothermal Microcalorimeter (manufactured by Thermometric AB company of Sweden). Analysis of these data revealed that different nucleotide mutations in -10 box sequence of RM07 fragment had different effect on the promoter activity. Our research also suggest that the microcalorimetric method is a very sensitive and easily performed method for investigation of promoter mutation.     

Interaction of calcium ions with α-elastin: An equilibrium dialysis,circular dichroism,and microcalorimetric study

The interaction of calcium ions with α-elastin has been investigated by equilibrium dialysis, CD, and microcalorimetric techniques. Consistent with literature data, it was found that the interaction in water is very poor. In trifluoroethanol (TFE), equilibrium dialysis experiments showed that calcium ions bind to ～-elastin with an association constant of ～250 L × mol^?1. Such a figure is not consistent with highly specific, highly selective binding. It was also found that the CD response is not directly proportional to the amount of bound calcium but depends on the protein concentration. From microcalorimetric experiments it was found that the heat effect relative to the binding process is of the order of 1.9 kcal/g ion. From this figure and from the binding constant, a positive ΔS value of about 17 e.u. was evaluated, leading to the conclusion that the binding process is entropy driven. From microcalorimetric measurements a ΔH of 1.5 kcal/residue was found for the calcium-induced conformational transition of the protein.     

Microcalorimetric evaluation of the efficacy of the alkaline treatment on the fermentation of straw

Summary A microcalorimetric study is proposed to follow the degradation of straw by a mixed bacterial culture. The effect of an alkali pretreatment of straw is described.     

Discriminant analysis of microcalorimetric data of bacterial growth

In this work a bacterial classification method based on the discriminant analysis of the microcalorimetric data provided by the growth power-time (p-t) curves is developed. This method is applied to classify several species of Enterobacteria of different origins, and the results are compared with those obtained by conventional techniques. The proposed analysis allows us to classify bacteria into species and discriminate among strains of the same species. The classification is carried out using one run of each isolate after standardization of inocula and growth conditions. The discrimination power of available microcalorimetric data is also discussed, and the most discriminant set of data is proposed as the input variables of the analysis. Finally, the advantages of microcalorimetry as a taxonomical technique are discussed.     

A microcalorimetric vessel for monitoring cytotoxic reactions in the micro-submicrowatt region

A microcalorimetric vessel for monitoring the initial phases of cytotoxic reactions in the micro-submicrowatt region has been designed and tested. The vessel is intended to be used with a multichannel microcalorimetric system from Thermometric, J?rf?lla, Sweden and can be built up stepwise in a modular way. The different functions of perfusion, stirring and addition of small amounts of soluble immune reactants can be used separately but also in combination. This is accomplished by the use of a vertical stirring mechanism and a reaction vessel of low volume, 200 microliters. The simplicity of the vessel permits an identical vessel to be used on the reference side, handled in parallel with the measuring vessel. No gas phase is present.     

Microcalorimetric characterization of seasonal metabolic trends in marine microcosms

A microcalorimetric and oximetric circulation system has been used to describe the emergence of seasonal adaptative changes occurring in marine microcosms at the water-sediment interface. The microcosms were prepared from three stations: one estuarine and two lagoonal. They were submitted to the same acute eutrophication, using peptone, and the evolutions shown by power-time and oxygen-time curves were compared over a 2-yr period. The metabolic heat productions and their oxidative counterparts are well correlated with seasonal trends. In summer, the microcalorimetric curves are typically unimodal, with very low dispersion, and a low thermodynamic steady state is attained in a few hours (40–50 μW), indicating an efficient, integrated regulatory mechanism; oxygen conditions evolute towards anoxia within 6 to 8 h. In winter, the power-time curves are typically sigmoid, with low dispersion; the thermodynamic steady state attained indicates a high maintenance energy requirement (140–150 μW), probably due to microbial populations less adapted to eutrophication stress. In winter, oxygen depletion is only partial and a plateau is attained within limits of 80 to 40% of initial saturation, and lasts 1 wk at least. Spring and autumn responses are very heterogeneous, varying from summer to winter types and displaying evolutive bimodal patterns. The sea-water-sediment interfaces from different estuarine and lagoonal habitats with distinct physical and chemical characteristics, but subjected to similar environmental and seasonal perturbations, show similar energetic patterns according to the seasons. It is proposed, as a working hypothesis, that the seasonal variations of the microcalorimetric response to experimental eutrophication are the expression of a global homeostatic adaptative memory, determined by natural environmental perturbations. Spring and autumn can be considered as intermediate periods within which a seasonal “adaptative memory” is replaced gradually by another one. The heterogeneity of the microcalorimetric response in spring and autumn microcosms could be related to an asynchronous maturation for the different components of the benthic ecosystem.