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121.
The effect of hydration andpH on the thermal stability of proteinase K was studied in the temperature range 310–450 K by differential scanning calorimetry. The dependences of the denaturation temperatureT
d, the specific enthalpy of denaturation H
d and the maximum of excess apparent specific heat capacityC
ex
max
upon the degree of hydrationh and thepH of the buffers used are presented. The relation betweenT
d andh is of the Flory-Garrett's type. By means of Ooi's model, the two components of the denaturation enthalpy arising from hydration and conformational change, respectively, were estimated. The fact that the specific denaturation enthalpy of proteinase K is very low may be attributed to its very low enthalpy of conformational change per heavy atom.Dedicated to Prof. Menachem Steinberg on the occasion of his 65th birthdayThis major project was supported by the National Natural Science Foundation of China. 相似文献
122.
G. Baert S. Hoste G. De Schutter N. De Belie 《Journal of Thermal Analysis and Calorimetry》2008,94(2):485-492
Four paste mixtures with varying replacement level of the cement content by fly ash have been studied. Due to fly ash, the
acceleration period decreased and a third hydration peak was noticed with isothermal calorimetry. The total heat after 7 days
increased with increasing fly ash content. From 1 to 7 days, thermogravimetry showed a higher chemically bound water and Ca(OH)2-content for the pastes with fly ash. Between 7 and 14 days the calcium hydroxide started to be depleted due to the pozzolanic
reaction. A unique relation was found between calcium hydroxide and total heat development. 相似文献
123.
B. Pacewska G. Blonkowski I. Wilińska 《Journal of Thermal Analysis and Calorimetry》2008,94(2):469-476
In this work, the pozzolanic and hydraulic properties of ashes originating from various sources were studied in model systems
such as ash and ash-lime pastes. The sources of studied ashes were: fluidized combustion of brown coal, pulverized combustion
of brown coal and pulverized combustion of hard coal. This article is a continuation of our previously published studies on
cement pastes with mentioned ashes.
The following experimental techniques were applied: calorimetry, thermal analysis (TG, DTG) and infrared absorption (IR).
Previously drawn conclusions relating to the reactivity of ashes in an environment containing Ca2+ ions were confirmed. According to these conclusions, an ash originating from fluidized combustion of coal exhibited higher
reactivity compared to other ashes from pulverized combustion. Pozzolanic and hydraulic properties of this ash were also confirmed.
Differences in the behaviour of ashes originating from pulverized combustion of various types of coal in the presence of water
and Ca2+ rich environment were demonstrated. 相似文献
124.
125.
在298.15 K下利用等温环境溶解反应热量计测定了离子液体C3MIBF4(四氟硼酸1-甲基-3-丙基咪唑)和C5MIBF4(四氟硼酸1-甲基-3-戊基咪唑)不同浓度水溶液的摩尔溶解焓(ΔsHm). 借助Pitzer电解质溶液理论, 得到了它们的标准摩尔溶解焓 和Pitzer焓参数: 和 , 并计算了表观相对摩尔焓. 根据Glasser理论计算了离子液体晶格能, 进而估算了离子液体C5MIBF4和C3MIBF4中正离子的水化焓分别为-171 kJ•mol-1 (C5MI+)和-207 kJ•mol-1 (C3MI+). 相似文献
126.
127.
Hao Yi Xian Zhang Yunliang Zhao Lingyun Liu Shaoxian Song 《Surface and interface analysis : SIA》2016,48(9):976-980
Molecular dynamics simulations (MDS) of montmorillonite (001)/water interface system were used for studying the hydration shell on the montmorillonite surface in this work. The study was performed on the simulation of concentration profile and self‐diffusion coefficients. The results have shown that there was a hydration shell on the surface with the thickness of approximately 1.74 nm, which was composed of six ordered water molecule layers, including ordered layers and transition layers. The water molecules in the shell were closely and orderly arranged than those in bulk water, leading to a higher concentration of water molecules. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
128.
We develop a new method for calculating the hydration free energy (HFE) of a protein with any net charge. The polar part of the energetic component in the HFE is expressed as a linear combination of four geometric measures (GMs) of the protein structure and the generalized Born (GB) energy plus a constant. The other constituents in the HFE are expressed as linear combinations of the four GMs. The coefficients (including the constant) in the linear combinations are determined using the three‐dimensional reference interaction site model (3D‐RISM) theory applied to sufficiently many protein structures. Once the coefficients are determined, the HFE and its constituents of any other protein structure are obtained simply by calculating the four GMs and GB energy. Our method and the 3D‐RISM theory give perfectly correlated results. Nevertheless, the computation time required in our method is over four orders of magnitude shorter. 相似文献
129.
Rapid approximate calculation of water binding free energies in the whole hydration domain of (bio)macromolecules 下载免费PDF全文
The evaluation of water binding free energies around solute molecules is important for the thermodynamic characterization of hydration or association processes. Here, a rapid approximate method to estimate water binding free energies around (bio)macromolecules from a single molecular dynamics simulation is presented. The basic idea is that endpoint free‐energy calculation methods are applied and the endpoint quantities are monitored on a three‐dimensional grid around the solute. Thus, a gridded map of water binding free energies around the solute is obtained, that is, from a single short simulation, a map of favorable and unfavorable water binding sites can be constructed. Among the employed free‐energy calculation methods, approaches involving endpoint information pertaining to actual thermodynamic integration calculations or endpoint information as exploited in the linear interaction energy method were examined. The accuracy of the approximate approaches was evaluated on the hydration of a cage‐like molecule representing either a nonpolar, polar, or charged water binding site and on α‐ and β‐cyclodextrin molecules. Among the tested approaches, the linear interaction energy method is considered the most viable approach. Applying the linear interaction energy method on the grid around the solute, a semi‐quantitative thermodynamic characterization of hydration around the whole solute is obtained. Disadvantages are the approximate nature of the method and a limited flexibility of the solute. © 2016 Wiley Periodicals, Inc. 相似文献
130.
Antonilêni F. D. Medeiros Ana Flávia O. Santos F. S. de Souza J. V. V. Procópio Márcia Ferraz Pinto R. O. Macêdo 《Journal of Thermal Analysis and Calorimetry》2007,87(2):377-382
Organobentonites were synthesized by treating Na-bentonites (Wyomingand Re?adiye) with cetylpyridinium chloride (CPC) using ion exchangemethod. The difference in the basal spacing by 0.65 Å and a higher massloss by 13.32% of organobentonite (Wyoming) in the temperature range 200–550°Ccomparing with that of organobentonite (Re?adiye) were in conformitywith the CEC values of organobentonites. The HOH stretching and bending peaksof bentonites became sharper following the treatment with the organo-cation.The intensity decrease of the Al–OH band for organobentonite (Re?adiye)and in particular, the significantly higher amount of m-cresolretained by the organobentonite of lower CEC than that by the organobentonite(Wyoming) indicate the influence of the CP cation on the adsorption process. 相似文献