食用色素苋菜红与牛血清白蛋白的相互作用研究

在模拟动物体生理条件和不同温度下,采用荧光、紫外光谱法来研究苋菜红(AMR)与牛血清白蛋白(BSA)结合反应。用Stern-Volmer和Lineweaver-Burk方程分别处理试验数据,发现BSA与AMR发生反应,生成新的复合物,属于静态荧光猝灭。实验求出反应时复合物的形成常数KLB、热力学参数与结合位点数,证明苋菜红与牛血清白蛋白的结合主要为静电作用力。位点竞争实验结果显示AMR与BSA的作用位置主要在BSA的Site I(sub-domain IIA)位。通过同步荧光光谱和三维荧光光谱法,探讨AMR对BSA构象的影响,实验结果表明,AMR使BSA酪氨酸残基和色氨酸残基所处微环境的极性减弱,疏水性增强。本文为探讨AMR的染色机理、毒理效应和生物学效应提供了重要信息。     

Investigation of bovine serum albumin denaturation using ultrasonic spectroscopy

The ability of ultrasound spectroscopy to characterise protein denaturation at relatively high concentrations and under conditions found in foods, is examined. Measurement of longitudinal sound velocity against concentration and frequency (20–160 MHz) for the bovine serum albumin monomer at pH 7.0 gave a frequency independent value for molecular compressibility of κ′ = 2.05 × 10⁻¹⁰ Pa⁻¹ at 25 °C, corresponding to a sound velocity for the BSA molecule of 1920 m s⁻¹. At 160 MHz, the longitudinal sound attenuation in BSA molecules is ∼5200 Np m⁻¹, a factor of 10 higher than in water. The excess attenuation of the solution over water was nearly 90 Np m⁻¹ at the highest measured volume fraction of 0.03 (or 3% v/v). Concentration-dependent ultrasound velocity (20–160 MHz) and attenuation (2–120 MHz) spectra were obtained over time for heated bovine serum albumin (BSA) solutions up to 40 mg/mL at neutral pH and at 25 °C. An acoustic scattering model was used which considered the solute molecules as scatterers of ultrasound, to determine the molecules’ sound velocity, compressibility, and attenuation properties. Mild heat treatment caused the molecule to organise into dimers and trimers, without change in sound velocity; implying that there is little or no change in secondary structure. Changes in attenuation spectra correlated with estimated molecular weight as determined through DLS and SEC measurements. During oligomerisation, the BSA molecules continue to behave acoustically as monomers.     

Effect of gamma-irradiation on the molecular properties of bovine serum albumin

To investigate the effect of oxygen radicals on the molecular properties of bovine serum albumin (BSA), the secondary and tertiary structures, molecular weight and optical anisotropy of BSA were examined after the irradiation of the protein at various doses. gamma-Irradiation of the protein solution caused the disruption of the ordered structure of protein molecules as well as degradation, cross-linking and aggregation of polypeptide chains. Fluorescence spectroscopy indicated that irradiation quenched the emission intensity excited at 280 nm. Fourier transform infrared spectroscopy (FTIR) indicated that irradiation caused transformation from beta-turns into beta-sheets. A light scattering study showed that increasing the radiation dose decreased the molecular weight of the protein. Optical anisotropy data showed that radiation changed the ordered structure of the protein. Ultraviolet absorption spectroscopy indicated that fragmentation and aggregation might occur in response to radiation exposure.     

青霉素与牛血清白蛋白结合作用机理的光谱法研究

模拟牛乳的生理环境pH6.6、37℃水浴的条件下,运用荧光光谱、同步荧光光谱和圆二色光谱法研究了青霉素与牛血清白蛋白(Bovine Serum Albumin,BSA)的相互作用。青霉素对BSA的猝灭机制属于静态猝灭,并发生分子间非辐射能量转移。热力学数据显示,二者之间的作用力主要为氢键作用;同步荧光光谱表明,青霉素与蛋白质中接近色氨酸残基的区域发生了相互作用;圆二色光谱法研究蛋白二级结构结果显示,青霉素与蛋白质结合会改变蛋白质的构象,进一步说明了青霉素在牛乳会与蛋白质作用形成稳定复合物。     

山梨酸钾与牛血清白蛋白相互作用的研究

在模拟动物体生理条件下,用荧光光谱、三维荧光光谱、同步荧光光谱、紫外-可见吸收光谱法等研究了在不同温度下,山梨酸钾(PSS)与牛血清白蛋白(BSA)结合反应的光谱行为。试验发现,PSS对BSA有较强的荧光猝灭作用。用Stern-Volmer和Lineweaver-Burk方程及热力学方程分别处理试验数据,发现BSA与PSS发生反应生成了新的复合物,属于静态荧光猝灭,得到了它们相互作用的生成常数KLB(8.421×103L.mol-1)、热力学参数(ΔHθ=-3.595kJ.mol-1,ΔSθ=63.26 J.K-1,ΔGθ=-22.73kJ.mol-1)和结合位点数(0.970)等。位点竞争实验结果显示PSS与BSA的作用位置主要在BSA的SiteI(sub-dom ain IIA)位。证明二者主要靠静电作用力结合,同时用三维荧光光谱及同步荧光光谱法探讨了PSS对BSA构象的影响,为研究PSS的毒性和生物学效应提供了重要信息。     

牛血清蛋白的超滤提取工艺研究

采用超滤技术提取牛血中的血清蛋白,主要研究了超滤液温度、超滤压力、超滤液pH和超滤时间对牛血清蛋白提取时膜通量、提取率和得率的影响。实验结果表明,超滤技术可应用于牛血清蛋白的提取,其最佳提取工艺参数为超滤液温度30℃,超滤压力0.1MPa,超滤液pH6.5,超滤时间20min,在此提取工艺参数条件下提取牛血清蛋白时,膜通量达54.58L/m2.h,牛血清蛋白提取率达98.13%,得率达24.09g/L。     

Specific release of Albutensins from bovine and human serum albumin

Bovine Albutensin (BA) and human Albutensin (HA) represent f(208–216) of bovine serum albumin (BSA) and f(210–218) of human serum albumin (HSA), respectively. The release of BA and HA was studied during tryptic digestion of serum albumins in solutions at different pH values. Specific release of either BA or HA was achieved by tryptic hydrolysis of serum albumins in 0.1 m NaH₂PO₄ solution adjusted to pH 3.5. Under these conditions, about 29–50% of the theoretical maximum of BA and 18–23% of the theoretical maximum of HA were released at high purity after 18 h digestion. Heat treatment of BSA (90 °C for 1–60 min) prior to tryptic hydrolysis (pH 3.5) did not improve the release of Albutensins. Under the same heating conditions, Albutensin from either BSA or HSA proved to be stable. Tryptic hydrolysates at pH 3.5 of serum albumins were submitted to simulated gastro-intestinal digestion. BA and HA were stable under peptic hydrolysis whilst they were almost completely hydrolysed by Corolase PP™.     

Isolation of bovine serum albumin from whey using affinity chromatography

The adsorption of bovine serum albumin (BSA) to a chromatography resin with immobilised llama antibody fragments as affinity ligands was investigated. The maximum adsorption capacity of the affinity resin was 21.6 mg mL⁻¹ with a Langmuir equilibrium constant of 20.4 mg mg⁻¹. Using packed bed chromatography, BSA was adsorbed from pure BSA solutions. Recovery was achieved by desorption at pH 3. In experiments with initial BSA concentrations of 1 mg mL⁻¹ and 0.1 mg mL⁻¹, BSA could be concentrated to 6.9 and 7.7 mg mL⁻¹, respectively. BSA was also isolated from filtered bovine cheese whey containing less than 0.1 mg mL⁻¹ BSA. The purified BSA was in this case concentrated to 7.4 mg mL⁻¹ BSA. The presence of other components in the feedstock did not alter the adsorption capacity of the affinity resin. The results show that high recovery combined with high purity can be obtained using affinity chromatography.     

三种多酚与牛血清蛋白相互作用的初步研究

采用紫外光谱法、荧光光谱法、圆二色谱法、同步荧光光谱法等方法分析异荭草素、鞣花酸和安石榴苷与牛血清蛋白(bovine serum albumin,BSA)的相互作用。结果表明,三种多酚类化合物对BSA的荧光猝灭机制主要为静态猝灭;与3种多酚结合后,BSA的构象发生变化,异荭草素与BSA的结合位点比例约为2∶1,安石榴苷、鞣花酸与BSA的结合位点比例约为1∶1;异荭草素、安石榴苷、鞣花酸与BSA相互作用的主要作用力初步确定为疏水作用力,并且此3种多酚与BSA之间的结合主要是吸热和熵驱动的反应。3种多酚均与牛血清蛋白产生不同程度的结合,为蛋白质与多酚复合物的研究提供了理论支撑。     

Catalysis of the sorbic acid–thiol reaction by bovine serum albumin

The effect of bovine serum albumin (BSA, 0–4%, w/v) in increasing the rate of reaction of sorbic acid with mercaptoethanol, mercaptoacetic acid, cysteine and glutathione (pH 5.0, 40°C) is comparable to that of the nonionic surfactant, Tween 80. For cysteine and glutathione, BSA has a similar effect to that of the cationic surfactant dodecyltrimethylammonium bromide, but is less effective for mercaptoethanol and mercaptoacetic acid. These preliminary observations are interpreted in terms of interactions between the reactants and nonionic environments on the BSA molecule.     

氯化血红素与牛血清白蛋白作用的光谱性质研究

在模拟动物生理条件下,结合荧光光谱和吸收光谱研究了氯化血红素（hemin,Hmn）与牛血清白蛋白（BSA）间的结合作用。分析了反应的结合常数（K=2.48×107L/mol）和结合位点（n=1.25）,确定了氯化血红素对牛血清白蛋白的荧光猝灭过程的猝灭类型。根据Fdrster的偶极-偶极非辐射能量转移理论,计算出结合位置距离212位色氨酸残基0.99nm。同时用三维荧光光谱及同步荧光光谱法探讨了Hmn对BSA构象的影响。      

Iron complexation to carboxyl groups in a bovine serum albumin digest

Protein is known to aid iron absorption from foods. The possible complexation occurring between iron and an in-vitro protein digest was studied by pH titration and by measuring the concentration of sulphydryl, amino and carboxyl groups in the presence and absence of ferrous and ferric iron. Complexation of iron was shown to occur with the protein digestion products and the carboxyl groups were identified as a site of complexation.     

牛血清蛋白对纤维素酶水解小麦秸秆的影响

在以分别被稀硫酸和氢氧化钠处理的小麦秸秆为底物进行纤维素酶解时添加牛血清蛋白（BSA）来评估BSA对酶解的影响,当接入纤维素酶40Ug秸秆,添加牛血清蛋白0.04g时,反应48h,还原糖得率分别提高30%和22%,添加牛血清蛋白后酸处理的秸秆水解速率更快,酶解液中酶失活趋势减小,以滤纸为底物测定纤维素酶活力时添加牛血清蛋白能将酶活提高1倍以上,从而推断牛血清蛋白可以提高纤维素酶的稳定性并减少酶因吸附木质素而失活,提高酶的水解效率。     

Effect of succinylation on the functional and physicochemical properties of bovine serum albumin

Bovine serum albumin was modijed with succinic anhydride so that 50 or 82% of lysine residues were acylated. The structural alterations caused by modification were examined by pH titration, electrophoretic patterns, circular dichroism, amino acid analysis, and the measurement of amino, sulphydryl and hydrophobic groups. Changes in these physicochemical properties were related to inferior whipping, emulsification and gelling properties of succinylated bovine serum albumin compared with the native protein.     

Interference of lipid with determination of bovine serum albumin by electroimmunodiffusion

Electroimmunodiffusion of ultra-high-temperature processed milk demonstrated an apparent increase in bovine serum albumin at some processing temperatures. The cause of the phenomenon was traced to the lipid component of the milk. Caproic acid was used in model studies to evaluate lipid effects in unheated and heated systems. Addition of caproic acid to bovine serum albumin without heat treatment reduced the apparent concentration of bovine serum albumin. Heating at 78 degrees C resulted in an initial increase in the apparent bovine serum albumin concentration, followed by a decrease with further heating. These results indicate that the reaction of specific antibody with bovine serum albumin in milk is inhibited by lipid and that this inhibition is reversed by heat treatments below that causing marked conformational changes in the protein.     

Impact of sorbitol on the thermostability and heat-induced gelation of bovine serum albumin

The influence of sorbitol (0–40 wt.%) on the thermal denaturation and gelation of bovine serum albumin (BSA, pH 7.0) in aqueous solution has been studied. The effect of sorbitol on heat denaturation of 0.5 wt.% BSA solutions was measured using ultrasensitive differential scanning calorimetry. The unfolding process was irreversible and was characterized by the thermal denaturation temperature (T_m). As the sorbitol concentration increased from 0 to 40 wt.%, T_m increased from 73.0 to 80.9 °C. The rise in T_m was attributed to the increased thermal stability of the globular state of BSA relative to its native state. The dynamic shear rheology of 4 wt.% BSA solutions containing 200 mM NaCl was monitored as they were heated from 30 to 90 °C at 1.5 °C min⁻¹, held at 90 °C for 120 min, and then cooled back to 30 °C at −1.5 °C min⁻¹. Sorbitol increased the protein gelation temperature (ΔT_gel +10 °C for 40 wt.% sorbitol), decreased the isothermal gelation rate at 90 °C, but increased the final shear modulus of the gels cooled to 30 °C. The impact of sorbitol on gel characteristics was attributed to its ability to increase protein thermal stability, increase the attractive force between proteins and decrease the protein–protein collision frequency.     

Effect of thiolation on the physicochemical and functional properties of bovine serum albumin

The effects of the attachment of homocysteine residues, to either 16 or 21 amino groups of bovine serum albumin (BSA), on the physicochemical and functional properties were studied. Both thiolated protein derivatives had a lower isoelectric point, hydrophobicity and α-helix conformation compared with the native protein. Polyacrylamide gel electrophoresis indicated that modification of the proteins resulted in a mixture of products. Thiolation impaired the whipping and gelling properties of bovine serum albumin but there was little change in the emulsification properties. It was concluded that increasing the available sulphydryl groups did not promote disulphide/ sulphydryl interchange reactions leading to enhanced functional properties: on the contrary, the blocking of amino groups was instrumental in impairing the whipping and gelling properties.     

苏丹Ⅰ与牛血清白蛋白的相互作用研究

用荧光光谱法和紫外-可见吸收光谱法研究了苏丹与牛血清白蛋白(BSA)结合反应的光谱行为,发现苏丹对BSA有较强的荧光猝灭作用,且苏丹的紫外吸收光谱和BSA的荧光发射光谱有一定程度的重叠,据此得出了其结合反应的结合常数、结合位点数和基本热力学参数等,并研究了二者的相互作用机理。     

怀山药多糖及怀牛膝皂甙与蛋白质作用研究

利用紫外可见分光光度法对怀牛膝皂甙和怀山药多糖与牛血清白蛋白（BSA）的相互作用进行研究.结果表明,牛血清白蛋白的吸光强度随怀牛膝皂甙和怀山药多糖加入量的增大而增大,并且最大吸收峰位置发生红移.