The denaturational behaviour of bovine β-lactoglobulin B has been studied in solutions containing guanidine hydrochloride by differential scanning calorimetry. The experiments have shown that complete peaks of cold d...The denaturational behaviour of bovine β-lactoglobulin B has been studied in solutions containing guanidine hydrochloride by differential scanning calorimetry. The experiments have shown that complete peaks of cold denaturation can be recorded also in high concentration of protein solutions. The cold denaturation and the renaturation of the protein are reproducible, but the thermal denaturation is irreversible. The activation energy of thermal denaturation calculated is about 285 kJ/mol.展开更多
The thermal denaturation of superoxide dismutase (SOD) from bovine erythrocytes was studied at various pH values of different buffers and at various concentrations of solutions of two neutral salts by differential sca...The thermal denaturation of superoxide dismutase (SOD) from bovine erythrocytes was studied at various pH values of different buffers and at various concentrations of solutions of two neutral salts by differential scanning calorimetry. The experiments performed indicate that the PIPES is a buffer non-coordinating with the SOD, and that the binding of the anions studied influences more or less the thermal denaturation of SOD, but the effect on the oxidation form of SOD is more apparent. A new conformer of SOD with lower thermostability was discovered by the experiments performed in different buffers at certain pH values higher than the isoelectric point of SOD, or at higher concentrations of neutral salt solutions. The new conformer may be converted irreversibly into the usual conformer with high thermostability during heating. Based on the thermodynamic parameters obtained in distilled water and by thermodynamic analysis using the Ooi's model, it is revealed that the large enthalpy △Hdc contributed by the conformational transition itself is a factor for SOD to possess very high thermostability.展开更多
Many researchers have compared inactivation with conformational changes of a number of enzymes during denaturation by guanidine hydrochloride and urea. The results obtained show that inactivation occurs before noticea...Many researchers have compared inactivation with conformational changes of a number of enzymes during denaturation by guanidine hydrochloride and urea. The results obtained show that inactivation occurs before noticeable conformational change of the enzyme molecule as a whole can be detected. The inactivation rate constants展开更多
Aggregation-induced thermally activated delayed fluorescence(TADF)phenomena have attracted extensive attention recently.In this paper,several theoretical models including monomer,dimer,and complex are used for the exp...Aggregation-induced thermally activated delayed fluorescence(TADF)phenomena have attracted extensive attention recently.In this paper,several theoretical models including monomer,dimer,and complex are used for the explanation of the luminescent properties of(R)-5-(9H-carbazol-9-yl)-2-(1,2,3,4-tetrahydronaphthalen-1-yl)isoindoline-1,3-dione((R)-ImNCz),which was recently reported[Chemical Engineering Journal 418129167(2021)].The polarizable continuum model(PCM)and the combined quantum mechanics and molecular mechanics(QM/MM)method are adopted in simulation of the property of the molecule in the gas phase,solvated in acetonitrile and in aggregation states.It is found that large spin–orbit coupling(SOC)constants and a smaller energy gap between the first singlet excited state and the first triplet excited state(△E_(st))in prism-like single crystals(SC_(p)-form)are responsible for the TADF of(R)-lmNCz,while no TADF is found in block-like single crystals(SC_(b)-form)with a larger △E_(st).The multiple ultralong phosphorescence(UOP)peaks in the spectrum are of complex origins,and they are related not only to ImNCz but also to a minor amount of impurities(ImNBd)in the crystal prepared in the laboratory.The dimer has similar phosphorescence emission wavelengths to the(R)-lmNCz-SC_(p) monomers.The complex composed of(R)-lmNCz and(R)-lmNBd contributes to the phosphorescent emission peak at about 600 nm,and the phosphorescent emission peak at about 650 nm is generated by(R)-lmNBd.This indicates that the impurity could also contribute to emission in molecular crystals.The present calculations clarify the relationship between the molecular aggregation and the light-emitting properties of the TADF emitters and will therefore be helpful for the design of potentially more useful TADF emitters.展开更多
The effect of nanoparticle aggregation on the thermal conductivity of nanocomposites or nanofluids is typically nonnegligible. A universal model（Maxwell model） including nanoparticle aggregation is modified in order...The effect of nanoparticle aggregation on the thermal conductivity of nanocomposites or nanofluids is typically nonnegligible. A universal model（Maxwell model） including nanoparticle aggregation is modified in order to predict the thermal conductivity of nanocomposites more accurately. The predicted thermal conductivities of silica and titania nanoparticle powders are compared first with that measured by a hot-wire method and then with those in previous experimental works.The results show that there is good agreement between our model and experiments, and that nanoparticle aggregation in a nanocomposite enhances the thermal conductivity greatly and should not be ignored. Because it considers the effect of aggregation, our model is expected to yield precise predictions of the thermal conductivity of composites.展开更多
The thermal behaviors of oxygen-related complexes in boron doped Czochralski Silicon (Cz-Si) wafers at 450°C and 800°C were investigated using Fourier transform infrared spectroscopy (FTIR) and Hall mobility...The thermal behaviors of oxygen-related complexes in boron doped Czochralski Silicon (Cz-Si) wafers at 450°C and 800°C were investigated using Fourier transform infrared spectroscopy (FTIR) and Hall mobility measurements. Activation of thermal donors (TDs) at 450°C leads to a decrease of both mobility and majority carrier concentration using the four point probes configuration of Van Der Pauw. It was found that annealing at 450°C would possibly affect the electronic properties of the Si wafers via the formation of interstitial dioxygen defects (IO2i), which exhibit an IR absorption band positioned at 545 cm–1. A strengthening of the IR bands peaking at around 1595 cm–1, 1667 cm–1, 1720 cm–1 and 1765 cm–1 occurs at 450°C, while they disappear at 800°C. At high temperatures, the precipitation of interstitial oxygen becomes predominant over all other oxygen-related reactions. The dynamic of oxygen-thermal donor generation-annihilation in Cz-Si involving the formation of small oxygen clusters is discussed.展开更多
Refractory materials are subjected to mechanical and chemical loads during application,which respectively lead to fracture and corrosion. The understanding of the mechanical fracture and the microstructural modificati...Refractory materials are subjected to mechanical and chemical loads during application,which respectively lead to fracture and corrosion. The understanding of the mechanical fracture and the microstructural modification after progressive thermal shocks is necessary for the suitable design of high performance refractory materials.The fracture process zone can be divided into two areas,where different toughening mechanisms are likely to take place： the crack tip and the following process region called wake region. In this study,the emphasis is laid on the microstructural mechanisms occurring in the wake region of the crack and the crack tip. Therefore,functional aggregates,namely fused eutectic aggregates of Al2O3- ZrO 2- SiO 2and Al2O3- ZrO 2,and andalusite,are added to a model high alumina castable formulation based on tabular alumina. The discrepancy in thermal behavior between aggregates and matrix as well as phase transformation such as mullite formation favor further the nucleation of microcracks that reduce the stress field at the level of the crack tip. Two different grain fractions of tabular alumina（ 0. 2- 0. 6 mm or2. 24- 3. 00 mm） are substituted by these functional aggregates. After sintering at 1 500 ℃ for 6 h,the samplesare quenched up to 10 times in air without pressure from950 ℃ to room temperature. The resulting elastic properties are examined after each thermal shock cycle,as well as the residual bending strength after 0,1,3,5,7and 10 thermal shocks. These results are correlated with Scanning Electron Microscopy analyses after the different thermal shock cycles.展开更多
Influence of intramolecular π-π interaction on the luminescent properties of thermally activated delayed fluorescence（TADF） molecule（3, 5-bis（3,6-di-tert-butyl-9 H-carbazol-9-yl）-phenyl）（pyridin-4-yl） methan...Influence of intramolecular π-π interaction on the luminescent properties of thermally activated delayed fluorescence（TADF） molecule（3, 5-bis（3,6-di-tert-butyl-9 H-carbazol-9-yl）-phenyl）（pyridin-4-yl） methanone（DTCBPY） is theoretically studied by using the density functional theory（DFT） and time-dependent density functional theory（TD-DFT）.Four conformations（named as A, B, C, and D） of the DTCBPY can be found by relax scanning, and the configuration C corresponds to the luminescent molecule detected experimentally. Besides, we calculate the proportion of each conformation by Boltzmann distribution, high configuration ratios（44% and 52%） can be found for C and D. Moreover, C and D are found to exist with an intramolecular π-π interaction between one donor and the acceptor; the intramolecular interaction brings a smaller Huang-Rhys factor and reduced reorganization energy. Our work presents a rational explanation for the experimental results and demonstrates the importance of the intramolecular π-π interaction to the photophysical properties of TADF molecules.展开更多
There are several mechanical models to describe the DNA phenomenology. In this work the DNA denaturation is studied under thermodynamical and dynamical point of view using the well known Peyrard-Bishop model. The ther...There are several mechanical models to describe the DNA phenomenology. In this work the DNA denaturation is studied under thermodynamical and dynamical point of view using the well known Peyrard-Bishop model. The thermodynamics analysis using the transfer integral operator method is briefly reviewed. In particular, the lattice size is discussed and a conjecture about the minimum energy to denaturation is proposed. In terms of the dynamical aspects of the model, the equations of motion for the system are integrated and the results determine the energy density where the denatura- tion occurs. The behavior of the lattice near the phase transition is analyzed. The relation between the thermodynamical and dynamical results is discussed.展开更多
Protein denaturation is under intensive research, since it leads to neurological disorders of severe consequences. Avoiding denaturation and stabilizing the proteins in their native state is of great importance,especi...Protein denaturation is under intensive research, since it leads to neurological disorders of severe consequences. Avoiding denaturation and stabilizing the proteins in their native state is of great importance,especially when proteins are used as drug molecules or vaccines. It is preferred to add pharmaceutical excipients in protein formulations to avoid denaturation and thereby stabilize them. The present study aimed at using bile salts(BSs), a group of well-known drug delivery systems, for stabilization of proteins.Bovine serum albumin(BSA) was taken as the model protein, whose association with two BSs, namely sodium cholate(Na C) and sodium deoxycholate(Na DC), was studied. Denaturation studies on the preformed BSA-BS systems were carried out under chemical and physical denaturation conditions. Urea was used as the chemical denaturant and BSA-BS systems were subjected to various temperature conditions to understand the thermal(physical) denaturation. With the denaturation conditions prescribed here,the data obtained is informative on the association of BSA-BS systems to be hydrophobic and this effect of hydrophobicity plays an important role in stabilizing the serum albumin in its native state under both chemical and thermal denaturation.展开更多
Enzyme activity is strongly dependent on its conformational integrity. The present paper compares the inactivation and unfolding of green crab (Scylla serrata) alkaline phosphate during thermal denaturation. The resul...Enzyme activity is strongly dependent on its conformational integrity. The present paper compares the inactivation and unfolding of green crab (Scylla serrata) alkaline phosphate during thermal denaturation. The results show that inactivation takes place before noticeable conformational changes. This is in general accord with the suggestion previously made by Tsou, indicating that the active site of multi metal enzymes is situated in a region more flexible than the molecules as a whole.展开更多
基金This project was supported by the National Natural Science Foundation of China
文摘The denaturational behaviour of bovine β-lactoglobulin B has been studied in solutions containing guanidine hydrochloride by differential scanning calorimetry. The experiments have shown that complete peaks of cold denaturation can be recorded also in high concentration of protein solutions. The cold denaturation and the renaturation of the protein are reproducible, but the thermal denaturation is irreversible. The activation energy of thermal denaturation calculated is about 285 kJ/mol.
基金Project supported by the National Natural Science Foundation of China.
文摘The thermal denaturation of superoxide dismutase (SOD) from bovine erythrocytes was studied at various pH values of different buffers and at various concentrations of solutions of two neutral salts by differential scanning calorimetry. The experiments performed indicate that the PIPES is a buffer non-coordinating with the SOD, and that the binding of the anions studied influences more or less the thermal denaturation of SOD, but the effect on the oxidation form of SOD is more apparent. A new conformer of SOD with lower thermostability was discovered by the experiments performed in different buffers at certain pH values higher than the isoelectric point of SOD, or at higher concentrations of neutral salt solutions. The new conformer may be converted irreversibly into the usual conformer with high thermostability during heating. Based on the thermodynamic parameters obtained in distilled water and by thermodynamic analysis using the Ooi's model, it is revealed that the large enthalpy △Hdc contributed by the conformational transition itself is a factor for SOD to possess very high thermostability.
文摘Many researchers have compared inactivation with conformational changes of a number of enzymes during denaturation by guanidine hydrochloride and urea. The results obtained show that inactivation occurs before noticeable conformational change of the enzyme molecule as a whole can be detected. The inactivation rate constants
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11974216,11874242,21933002 and 11904210)Shandong Provincial Natural Science Foundation,China(Grant No.ZR2019MA056)+1 种基金the support of the Taishan Scholar Project of Shandong Provincethe project funded by China Postdoctoral Science Foundation(Grant No.2018M642689)。
文摘Aggregation-induced thermally activated delayed fluorescence(TADF)phenomena have attracted extensive attention recently.In this paper,several theoretical models including monomer,dimer,and complex are used for the explanation of the luminescent properties of(R)-5-(9H-carbazol-9-yl)-2-(1,2,3,4-tetrahydronaphthalen-1-yl)isoindoline-1,3-dione((R)-ImNCz),which was recently reported[Chemical Engineering Journal 418129167(2021)].The polarizable continuum model(PCM)and the combined quantum mechanics and molecular mechanics(QM/MM)method are adopted in simulation of the property of the molecule in the gas phase,solvated in acetonitrile and in aggregation states.It is found that large spin–orbit coupling(SOC)constants and a smaller energy gap between the first singlet excited state and the first triplet excited state(△E_(st))in prism-like single crystals(SC_(p)-form)are responsible for the TADF of(R)-lmNCz,while no TADF is found in block-like single crystals(SC_(b)-form)with a larger △E_(st).The multiple ultralong phosphorescence(UOP)peaks in the spectrum are of complex origins,and they are related not only to ImNCz but also to a minor amount of impurities(ImNBd)in the crystal prepared in the laboratory.The dimer has similar phosphorescence emission wavelengths to the(R)-lmNCz-SC_(p) monomers.The complex composed of(R)-lmNCz and(R)-lmNBd contributes to the phosphorescent emission peak at about 600 nm,and the phosphorescent emission peak at about 650 nm is generated by(R)-lmNBd.This indicates that the impurity could also contribute to emission in molecular crystals.The present calculations clarify the relationship between the molecular aggregation and the light-emitting properties of the TADF emitters and will therefore be helpful for the design of potentially more useful TADF emitters.
基金Project supported by the Fundamental Research Funds for the Central Universities of China(Grant No.2015XKMS062)
文摘The effect of nanoparticle aggregation on the thermal conductivity of nanocomposites or nanofluids is typically nonnegligible. A universal model（Maxwell model） including nanoparticle aggregation is modified in order to predict the thermal conductivity of nanocomposites more accurately. The predicted thermal conductivities of silica and titania nanoparticle powders are compared first with that measured by a hot-wire method and then with those in previous experimental works.The results show that there is good agreement between our model and experiments, and that nanoparticle aggregation in a nanocomposite enhances the thermal conductivity greatly and should not be ignored. Because it considers the effect of aggregation, our model is expected to yield precise predictions of the thermal conductivity of composites.
基金gratefully thank the Tunisian Ministry of Higher Education and Scientific Research for the financial support.
文摘The thermal behaviors of oxygen-related complexes in boron doped Czochralski Silicon (Cz-Si) wafers at 450°C and 800°C were investigated using Fourier transform infrared spectroscopy (FTIR) and Hall mobility measurements. Activation of thermal donors (TDs) at 450°C leads to a decrease of both mobility and majority carrier concentration using the four point probes configuration of Van Der Pauw. It was found that annealing at 450°C would possibly affect the electronic properties of the Si wafers via the formation of interstitial dioxygen defects (IO2i), which exhibit an IR absorption band positioned at 545 cm–1. A strengthening of the IR bands peaking at around 1595 cm–1, 1667 cm–1, 1720 cm–1 and 1765 cm–1 occurs at 450°C, while they disappear at 800°C. At high temperatures, the precipitation of interstitial oxygen becomes predominant over all other oxygen-related reactions. The dynamic of oxygen-thermal donor generation-annihilation in Cz-Si involving the formation of small oxygen clusters is discussed.
基金the Federation for International Refractory Research and Education ( FIRE) for having supported this academic research study and for having promoted these student exchangesthe German Research Foundation (DFG) +1 种基金supported in the framework of the priority program 1418 "Refractory - Initiative to Reduce Emissions"ALTEO,KERl NEOS,DAMREC,REFEL and BASF for supporting this work with raw materials
文摘Refractory materials are subjected to mechanical and chemical loads during application,which respectively lead to fracture and corrosion. The understanding of the mechanical fracture and the microstructural modification after progressive thermal shocks is necessary for the suitable design of high performance refractory materials.The fracture process zone can be divided into two areas,where different toughening mechanisms are likely to take place： the crack tip and the following process region called wake region. In this study,the emphasis is laid on the microstructural mechanisms occurring in the wake region of the crack and the crack tip. Therefore,functional aggregates,namely fused eutectic aggregates of Al2O3- ZrO 2- SiO 2and Al2O3- ZrO 2,and andalusite,are added to a model high alumina castable formulation based on tabular alumina. The discrepancy in thermal behavior between aggregates and matrix as well as phase transformation such as mullite formation favor further the nucleation of microcracks that reduce the stress field at the level of the crack tip. Two different grain fractions of tabular alumina（ 0. 2- 0. 6 mm or2. 24- 3. 00 mm） are substituted by these functional aggregates. After sintering at 1 500 ℃ for 6 h,the samplesare quenched up to 10 times in air without pressure from950 ℃ to room temperature. The resulting elastic properties are examined after each thermal shock cycle,as well as the residual bending strength after 0,1,3,5,7and 10 thermal shocks. These results are correlated with Scanning Electron Microscopy analyses after the different thermal shock cycles.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11374195 and 21403133)Taishan Scholar Project of Shandong Normal University,China+1 种基金the Promotive Research Fund for Excellent Young and Middle-aged Scientists of Shandong Province,China(Grant No.BS2014cl001)the China Postdoctoral Science Foundation(Grant No.2014M560571)
文摘Influence of intramolecular π-π interaction on the luminescent properties of thermally activated delayed fluorescence（TADF） molecule（3, 5-bis（3,6-di-tert-butyl-9 H-carbazol-9-yl）-phenyl）（pyridin-4-yl） methanone（DTCBPY） is theoretically studied by using the density functional theory（DFT） and time-dependent density functional theory（TD-DFT）.Four conformations（named as A, B, C, and D） of the DTCBPY can be found by relax scanning, and the configuration C corresponds to the luminescent molecule detected experimentally. Besides, we calculate the proportion of each conformation by Boltzmann distribution, high configuration ratios（44% and 52%） can be found for C and D. Moreover, C and D are found to exist with an intramolecular π-π interaction between one donor and the acceptor; the intramolecular interaction brings a smaller Huang-Rhys factor and reduced reorganization energy. Our work presents a rational explanation for the experimental results and demonstrates the importance of the intramolecular π-π interaction to the photophysical properties of TADF molecules.
基金grateful to Capes and CNPq for the financial support.
文摘There are several mechanical models to describe the DNA phenomenology. In this work the DNA denaturation is studied under thermodynamical and dynamical point of view using the well known Peyrard-Bishop model. The thermodynamics analysis using the transfer integral operator method is briefly reviewed. In particular, the lattice size is discussed and a conjecture about the minimum energy to denaturation is proposed. In terms of the dynamical aspects of the model, the equations of motion for the system are integrated and the results determine the energy density where the denatura- tion occurs. The behavior of the lattice near the phase transition is analyzed. The relation between the thermodynamical and dynamical results is discussed.
基金DSTSERB,India(SB/FT/CS-032/2012),for the financial support
文摘Protein denaturation is under intensive research, since it leads to neurological disorders of severe consequences. Avoiding denaturation and stabilizing the proteins in their native state is of great importance,especially when proteins are used as drug molecules or vaccines. It is preferred to add pharmaceutical excipients in protein formulations to avoid denaturation and thereby stabilize them. The present study aimed at using bile salts(BSs), a group of well-known drug delivery systems, for stabilization of proteins.Bovine serum albumin(BSA) was taken as the model protein, whose association with two BSs, namely sodium cholate(Na C) and sodium deoxycholate(Na DC), was studied. Denaturation studies on the preformed BSA-BS systems were carried out under chemical and physical denaturation conditions. Urea was used as the chemical denaturant and BSA-BS systems were subjected to various temperature conditions to understand the thermal(physical) denaturation. With the denaturation conditions prescribed here,the data obtained is informative on the association of BSA-BS systems to be hydrophobic and this effect of hydrophobicity plays an important role in stabilizing the serum albumin in its native state under both chemical and thermal denaturation.
文摘Enzyme activity is strongly dependent on its conformational integrity. The present paper compares the inactivation and unfolding of green crab (Scylla serrata) alkaline phosphate during thermal denaturation. The results show that inactivation takes place before noticeable conformational changes. This is in general accord with the suggestion previously made by Tsou, indicating that the active site of multi metal enzymes is situated in a region more flexible than the molecules as a whole.
