大豆分离蛋白(soybean protein isolate,SPI)基乳液凝胶在食品工业中应用广泛。在商品化SPI生产过程中,不可避免会发生一定程度的热变性和聚集,对谷氨酰胺转氨酶(transglutaminase,TGase)交联蛋白产生影响。为探究不同热变性程度的SPI对...大豆分离蛋白(soybean protein isolate,SPI)基乳液凝胶在食品工业中应用广泛。在商品化SPI生产过程中,不可避免会发生一定程度的热变性和聚集,对谷氨酰胺转氨酶(transglutaminase,TGase)交联蛋白产生影响。为探究不同热变性程度的SPI对TGase诱导SPI乳液凝胶的影响,制备了不同热处理温度的SPI,研究其乳化性、凝胶强度、持水/油性、凝胶形态,以及SPI浓度、油浓度对SPI乳液凝胶性质的影响。结果表明:随着热处理温度的增加,SPI稳定乳液的乳化活性和乳化稳定性呈显著增加趋势。95℃热处理显著增强了乳液凝胶的凝胶性能,其凝胶硬度是天然蛋白乳液凝胶的2.2倍。对于95℃热处理的SPI乳液凝胶,随着蛋白浓度或油浓度的增大,凝胶强度显著增加,气孔逐渐增大;所有样品均具有优异的持水性和持油性。SPI在经过热变性(95℃)处理后有利于经TGase诱导形成SPI乳液凝胶。展开更多
The cold and heat denaturations of bovine β-lactoglobuhn A (β-lg A) has been studied in solutions of guanidine hydrochloride (GuHCl) by differential scanning calorimelry (DSC) The experimental results are presented ...The cold and heat denaturations of bovine β-lactoglobuhn A (β-lg A) has been studied in solutions of guanidine hydrochloride (GuHCl) by differential scanning calorimelry (DSC) The experimental results are presented and discussed.It is shown that the number of protons bound by the monomeric molecules of β-lg A was unchanged before and after its heat denaturation below pH 3,and that the activation energy of the heat denaturation was depressed owing to the presence of GuHCl.In the solutions with 2.50 and 3.06 mol/L of GuHCl,both the cold and heat denat-urations of β-lg A were observed.In comparison with the heat denaturation,the activation energy of cold denaturation was far lower and the number of GuHCl molecules bound by the unfolded polypeptide chains after cold denaturation increased a lot.The absolute value of the enthalpy of cold denaturation was larger than that of heat denaturation It was found by the analysis that the contribution to the total denaturational enthalpy of conformational change itself of the monomeric molecules of β-lg A was the lowest among the globulins,according to the average of the number of heavyatoms.展开更多
IN the field of thermodynamics of protein solutions, there are two kinds of denaturation induced by temperature changes. One of them is the commonest heat denaturation induced by temperature increasing and accompanied...IN the field of thermodynamics of protein solutions, there are two kinds of denaturation induced by temperature changes. One of them is the commonest heat denaturation induced by temperature increasing and accompanied by a heat absorption and an increase of enthalpy and entropy. The other is cold denaturation, predicted by Brandts over thirty years ago: the compact ordered structure of protein molecules in the native state is induced into a展开更多
Heat denaturation is an important technique in the study of the structure and function of photosynthetic proteins. Heat denaturation of photosystem II (PSII) membrane was studied using circular dichroism (CD) spect...Heat denaturation is an important technique in the study of the structure and function of photosynthetic proteins. Heat denaturation of photosystem II (PSII) membrane was studied using circular dichroism (CD) spectroscopy, differential scanning calorimetry (DSC) and oxygen electrode. Complete loss of oxygen evolving activity of the PSII membrane was observed at temperatures below 45℃ . The decrease of excitonic interaction between chlorophyll molecules occurred more rapidly than the change of the protein secondary structure of the PSII membrane at temperatures above 45℃ . The results indicate that the protein secondary structure of the membrane proteins in PSII membranes is more stable than the excitonic interaction between chlorophyll molecules during heat denaturation. 展开更多
The heat denaturation of the rice mitochondrial DNA in two different media has been studied by using ultraviolet absorption spectrometry over the temperature range 25-85 ℃ The heat denaturation curve of the rice mito...The heat denaturation of the rice mitochondrial DNA in two different media has been studied by using ultraviolet absorption spectrometry over the temperature range 25-85 ℃ The heat denaturation curve of the rice mitochondrial DNA in 0.15 mol.L-1 NaCl solution has been obtained and the thermodyndric functions of the rice mitochondrial DNA in the heat denaturation process have been calculated. Furthermore,the relationship between these thermodyndric functions and the structure of the rice mitochondrial DNA has been discussed preliminarily.展开更多
文摘大豆分离蛋白(soybean protein isolate,SPI)基乳液凝胶在食品工业中应用广泛。在商品化SPI生产过程中,不可避免会发生一定程度的热变性和聚集,对谷氨酰胺转氨酶(transglutaminase,TGase)交联蛋白产生影响。为探究不同热变性程度的SPI对TGase诱导SPI乳液凝胶的影响,制备了不同热处理温度的SPI,研究其乳化性、凝胶强度、持水/油性、凝胶形态,以及SPI浓度、油浓度对SPI乳液凝胶性质的影响。结果表明:随着热处理温度的增加,SPI稳定乳液的乳化活性和乳化稳定性呈显著增加趋势。95℃热处理显著增强了乳液凝胶的凝胶性能,其凝胶硬度是天然蛋白乳液凝胶的2.2倍。对于95℃热处理的SPI乳液凝胶,随着蛋白浓度或油浓度的增大,凝胶强度显著增加,气孔逐渐增大;所有样品均具有优异的持水性和持油性。SPI在经过热变性(95℃)处理后有利于经TGase诱导形成SPI乳液凝胶。
基金Project supported by the National Natural Science Foundation of Chinaby the fund for excellent items under Director of the Institute of Chemistry
文摘The cold and heat denaturations of bovine β-lactoglobuhn A (β-lg A) has been studied in solutions of guanidine hydrochloride (GuHCl) by differential scanning calorimelry (DSC) The experimental results are presented and discussed.It is shown that the number of protons bound by the monomeric molecules of β-lg A was unchanged before and after its heat denaturation below pH 3,and that the activation energy of the heat denaturation was depressed owing to the presence of GuHCl.In the solutions with 2.50 and 3.06 mol/L of GuHCl,both the cold and heat denat-urations of β-lg A were observed.In comparison with the heat denaturation,the activation energy of cold denaturation was far lower and the number of GuHCl molecules bound by the unfolded polypeptide chains after cold denaturation increased a lot.The absolute value of the enthalpy of cold denaturation was larger than that of heat denaturation It was found by the analysis that the contribution to the total denaturational enthalpy of conformational change itself of the monomeric molecules of β-lg A was the lowest among the globulins,according to the average of the number of heavyatoms.
文摘IN the field of thermodynamics of protein solutions, there are two kinds of denaturation induced by temperature changes. One of them is the commonest heat denaturation induced by temperature increasing and accompanied by a heat absorption and an increase of enthalpy and entropy. The other is cold denaturation, predicted by Brandts over thirty years ago: the compact ordered structure of protein molecules in the native state is induced into a
基金Supported by the State Key Basic Research and Development Plan (No.G19980 10 10 0 ) the National Natural Science Foundation of China(No.3 9890 3 90 )
文摘Heat denaturation is an important technique in the study of the structure and function of photosynthetic proteins. Heat denaturation of photosystem II (PSII) membrane was studied using circular dichroism (CD) spectroscopy, differential scanning calorimetry (DSC) and oxygen electrode. Complete loss of oxygen evolving activity of the PSII membrane was observed at temperatures below 45℃ . The decrease of excitonic interaction between chlorophyll molecules occurred more rapidly than the change of the protein secondary structure of the PSII membrane at temperatures above 45℃ . The results indicate that the protein secondary structure of the membrane proteins in PSII membranes is more stable than the excitonic interaction between chlorophyll molecules during heat denaturation.
文摘The heat denaturation of the rice mitochondrial DNA in two different media has been studied by using ultraviolet absorption spectrometry over the temperature range 25-85 ℃ The heat denaturation curve of the rice mitochondrial DNA in 0.15 mol.L-1 NaCl solution has been obtained and the thermodyndric functions of the rice mitochondrial DNA in the heat denaturation process have been calculated. Furthermore,the relationship between these thermodyndric functions and the structure of the rice mitochondrial DNA has been discussed preliminarily.
