胶乳微球与抗体蛋白相互作用机理的荧光光谱法分析

利用共价偶联的方法制备了胶乳-抗体蛋白复合物,并采用荧光光谱法对复合物的性质进行了研究,以揭示胶乳微球与抗体蛋白之间的相互作用机理。内源荧光光谱分析结果表明,共价偶联后,抗体蛋白的最大发射峰发生显著蓝移,最大发射峰强度显著降低,抗体蛋白的三级结构发生了一定的变化,胶乳微球与抗体蛋白之间的相互作用对抗体蛋白的内源荧光有显著的猝灭作用,猝灭效果随着偶联体系pH值以及胶乳浓度的增加而增强,猝灭机制为静态猝灭。外源荧光光谱分析结果表明,共价偶联后抗体蛋白的最大发射峰强度显著增强,且随着偶联体系pH值的升高,抗体蛋白的疏水性显著降低,随着胶乳浓度的增加,疏水性逐渐升高。     

咖啡酸与乳蛋白结合的光谱特性及结合物抗氧化活性变化

利用紫外光谱和荧光光谱技术评价了咖啡酸与乳蛋白(α-酪蛋白、β-酪蛋白、κ-酪蛋白、α-乳白蛋白、β-乳球蛋白)两者结合的结合常数、结合作用力、结合距离以及能量转移效率,通过二苯代苦味酰基(DPPH)自由基清除率和铁离子还原能力(FRAP)对两者结合导致的抗氧化活性变化进行了测定。结果表明咖啡酸会使乳蛋白发生内源性荧光猝灭。吉布斯自由能变ΔG<0,表明反应是自发进行的。其中咖啡酸与α-酪蛋白之间以静电引力结合(ΔH<0,ΔS>0),与β-酪蛋白、α-乳白蛋白的结合作用力为氢键(ΔH<0,ΔS<0),与κ-酪蛋白、β-乳球蛋白是以疏水作用力结合(ΔH>0,ΔS>0)。两者结合距离r0<7nm,符合非辐射能量转移条件,证明咖啡酸对乳蛋白的荧光猝灭是由于生成不发光的配合物而引起的静态猝灭。此外,两者结合导致咖啡酸的抗氧化能力受到不同程度的抑制。     

环丙沙星、氧氟沙星同时与牛血清白蛋白分子作用的荧光光谱

在pH=7.40的水溶液中,环丙沙星(CPFX)、氧氟沙星(OFLX)能够猝灭牛血清白蛋白(BSA)的荧光。当两种药物共存时BSA荧光被进一步猝灭。据此建立了利用荧光发光光谱法进行喹诺酮类药物CPFX与OFLX间相互作用的研究。结果表明:药物间存在相互作用,使药物与蛋白间的结合常数减小、结合稳定性下降,游离型药物含量增加,造成药效增强;药物对蛋白荧光的猝灭属于静态猝灭,药物与蛋白结合位点数约为1。根据Frster非辐射能量转移理论,确定了药物与蛋白之间的结合距离r7nm,属于非辐射能量转移。药物间的相互作用使r值增加,结合距离增大。同步荧光光谱研究表明药物间的相互作用对蛋白构象产生影响,使蛋白质分子伸展,疏水性降低。     

L-半胱氨酸修饰的金纳米粒子与牛血清白蛋白相互作用的荧光光谱研究

采用荧光猝灭光谱和同步荧光光谱研究了L-半胱氨酸修饰的金纳米粒子(Cys-GNPs)与牛血清白蛋白(BSA)间的相互作用。根据荧光猝灭相关方程计算了Cys-GNPs与BSA相互作用的结合常数和结合位点数,探讨了其荧光猝灭机制为静态猝灭,并且根据热力学参数确定了二者间的作用力类型,推断出Cys-GNPs和BSA间主要靠疏水作用力结合。同步荧光光谱表明,二者的相互作用没有导致牛血清白蛋白的构象及色氨酸残基的微环境发生明显变化。     

分子光谱法研究硫普罗宁修饰的CdTe量子点与血红蛋白相互作用

以N-(2-巯基丙酰基)-甘氨酸(硫普罗宁,TP)为稳定剂,采用水相法合成了荧光较好的水溶性CdTe量子点(TP-CdTe QDs)。本文通过共振瑞利散射光谱(RRS)、荧光光谱(FL)和紫外光谱(UV-Vis),探讨了TP-CdTe QDs与血红蛋白通过静电引力相互作用的机理.研究发现TP-CdTe QDs与血红蛋白通过静电引力相互作用以后,TP-CdTe QDs荧光猝灭发生猝灭同时荧光光谱发生蓝移,体系的共振瑞利散射光谱强度增大.血红蛋白通过静态猝灭,动态猝灭和光诱导电子转移的方式猝灭TP-CdTeQDs的荧光。同时对体系共振瑞利散射增强的原因进行了讨论。     

钙离子对酪蛋白胶束结构影响的光谱学研究

综合运用动态光散射光谱、荧光光谱和高效液相-紫外光谱法检测钙离子对酪蛋白胶束结构的影响。外源添加的钙离子的浓度从0增加至12 mmol·L-1的过程中,酪蛋白胶束的外源ANS荧光强度和浊度一直增大,但是其体积平均直径和胶束的多分散指数是一直下降。同时,当外源添加的钙螯合剂(柠檬酸根)离子的浓度从0 增加至12 mmol·L-1的过程中,酪蛋白胶束的外源ANS荧光强度和浊度一直减小,但是酪蛋白胶束的体积平均直径、胶束的多分散指数和胶束的稳定性是增大的。因此,在对酪蛋白胶束的结构影响方面,钙离子和柠檬酸根离起到了相反的作用。研究证实,外源钙离子可以有效地调节酪蛋白胶束的结构,进而改善其功能特性。     

硫酸头孢匹罗与牛血清白蛋白结合反应的发光机理

在人生理条件下,利用荧光猝灭法、同步荧光法及共振光散射法,分别研究了不同温度下硫酸头孢匹罗(CPS)与牛血清白蛋白(BSA)间的结合反应.结果表明:随着CPS浓度的增加,BSA的荧光、共振散射光依次降低,其荧光猝灭为静态猝灭过程并伴随非辐射能量转移作用.反应的结合常数为104数量级.结合位点数约为1;结合位点位于BSA...     

2,4-二硝基苯肼与牛血清白蛋白的相互作用

用荧光光谱研究了2,4-二硝基苯肼(DNPH)与牛血清白蛋白(BSA)的相互作用.实验结果表明,2,4-二硝基苯肼能导致BSA的内源荧光猝灭,猝灭机制为静态猝灭;根据热力学参数△H＜0、△S＜0,得出2,4-二硝基苯肼与BSA之间的主要作用力为氢键和范德华力;同步荧光的结果表明2,4-二硝基苯肼使BSA分子构象发生了改变,其分子内的色氨酸和酪氨酸残基疏水作用增强.     

叶酸与人血清白蛋白结合作用的光谱研究

在不同温度下的pH 7.4的Tris-HCl缓冲溶液体系中, 采用荧光光谱、紫外吸收光谱和同步荧光光谱研究了人血清蛋白与叶酸的相互作用。研究表明,这种相互作用使人血清白蛋白发生内源荧光猝灭,属于静态猝灭机制。通过计算得到人血清蛋白与叶酸在17和37 ℃下静态猝灭的猝灭速率常数分别为7.396 6×104和7.2652×104 L·mol-1、结合常数分别为7.50×104和1.98×105 L·mol-1、结合位点数均为1。根据Förster非辐射能量转移机理,求算出给体(HSA)与受体(叶酸)间的作用距离和能量转移效率分别为1.77和0.052 65 nm,并结合热力学参数说明了叶酸分子与人血清白蛋白的作用以疏水作用为主,同时也存在静电引力。利用同步荧光光谱研究了人血清蛋白与叶酸的相互作用中HSA的构象变化,发现色氨酸残基所处环境的疏水性降低,说明叶酸分子进入了人血清白蛋白的疏水腔中。     

荧光法研究木犀草素与人血清白蛋白的相互作用

用荧光光谱、同步荧光光谱和紫外吸收光谱方法,研究了木犀草素与人血清白蛋白（HSA）的相互作用。研究表明木犀草素对HSA有较强的荧光猝灭作用,根据不同温度下木犀草素对HSA的荧光猝灭作用,利用Stern-Volmer方程处理实验数据,表明木犀草素对HSA的荧光猝灭作用属于静态猝灭。根据Fōrster非辐射能量转移理论计算了木犀草素与HSA间的结合常数和结合位点数,求得了木犀草素与HSA间的结合距离r。热力学数据表明二者主要靠疏水作用力结合。同时用同步荧光光谱探讨了木犀草素对HSA构象的影响。     

Ultrasound assisted preparation of water in oil emulsions and their application in arsenic (V) removal from water in an emulsion liquid membrane process

Water in oil emulsions are prepared by using an ultra-sonication device and used in an emulsion liquid membrane process in order to recover arsenic (V) ions from an aqueous medium. The aim of this work is the investigation of the effect of emulsifier concentration and composition, and also sonication time on the emulsion droplet size and the extraction efficiency in order to obtain stable emulsions with small droplets that favor the extraction. Results show that ultrasonic waves reduce internal droplet size which enhances the extraction of arsenic. In addition, internal droplet size is decreased initially and then increased by increasing Span 80 concentration. On the other hand, by increasing Span 80 concentration, extraction amount is increased and then decreased. Furthermore, emulsifier blends provide more stability for the emulsion. Increasing concentration of Tween 20 as a hydrophilic emulsifier up to an optimum concentration decreases internal droplet size and increases extraction amount. By increasing sonication time up to 4 min, the internal droplet size is decreased and the extraction amount is increased. If sonication time is increased further, the internal droplet size is increased and the extraction amount is decreased.     

Comparison of oil-in-water emulsions prepared by ultrasound,high-pressure homogenization and high-speed homogenization

This study was designed to compare the properties of myofibrillar protein (MP) stabilized soybean oil-in-water emulsions fabricated by ultrasound-assisted emulsification (UAE), high-pressure homogenization (HPH) and high-speed homogenization (HSH). The emulsion properties, droplet characteristics, interfacial proteins, protein exposure extent, microrheological properties, multiple light scattering results, and 7 d storage stabilities of the three emulsions were specifically investigated. Our results indicate that UAE and HPH were better emulsification methods than HSH to obtain high-quality emulsions with higher emulsifying activity index (UAE 20.73 m²·g⁻¹, HPH 11.76 m²·g⁻¹ and HSH 6.80 m²·g⁻¹), whiteness (UAE 81.05, HPH 80.67 and HSH 74.09), viscosity coefficient (UAE 0.44 Pa·sⁿ, HPH 0.49 Pa·sⁿ and HSH 0.22 Pa·sⁿ), macroscopic viscosity index (UAE 2.31 nm⁻²·s, HPH 0.38 nm⁻²·s and HSH 0.34 nm⁻²·s), and storage stability, especially for the UAE. Furthermore, UAE was a more efficient emulsification method than HPH to prepare the fine MP-soybean oil emulsion. The protein-coated oil droplets were observed in the three emulsions. The emulsion droplet size of the UAE-fabricated emulsion was the lowest (0.15 μm) while the interfacial protein concentration (93.37%) and the protein exposure extent were the highest among the three emulsions. During the 7 d storage, no separation was observed for the UAE-fabricated emulsion, while the emulsions fabricated by HPH and HSH were separated after storage for 5 d and 2 h. Therefore, this work suggests that UAE could be a better method than HPH and HSH to fabricate MP-soybean oil emulsion.     

High-intensity ultrasound modified the functional properties of Neosalanx taihuensis myofibrillar protein and improved its emulsion stability

This study aimed to investigate the effects of high-intensity ultrasound treatment on the functional properties and emulsion stability of Neosalanx taihuensis myofibrillar protein (MP). The results showed that the carbonyl groups, emulsification properties, intrinsic fluorescence intensity, and surface hydrophobicity of the ultrasound treated MP solution were increased compared to the MP without ultrasound treatment. The results of secondary structure showed that the ultrasound treatment could cause a huge increase of β-sheet and a decline of α-helix of MP, indicating that ultrasound induced molecular unfolding and stretching. Moreover, ultrasound reduced the content of total sulfhydryl and led to a certain degree of MP cross-linking. The microscopic morphology of MP emulsion indicated that the emulsion droplet decreased with the increase of ultrasound power. In addition, ultrasound could also increase the storage modulus of the MP emulsion. The results for the lipid oxidation products indicated that ultrasound significantly improved the oxidative stability of N. taihuensis MP emulsions. This study offers an important reference theoretically for the ultrasound modification of aquatic proteins and the future development of N. taihuensis deep-processed products represented by surimi.     

Effects of high hydrostatic pressure on secondary structure and emulsifying behavior of sweet potato protein

In this study, secondary structures of sweet potato protein (SPP) after high hydrostatic pressure (HHP) treatment (200–600?MPa) were evaluated and emulsifying properties of emulsions with HHP-treated SPP solutions in different pH values (3, 6, and 9) were investigated. Circular dichroism analysis confirmed the modification of the SPP secondary structure. Surface hydrophobicity increased at pH 3 and decreased at 6 and 9. Emulsifying activity index at pH 6 increased with an increase in pressure, whereas emulsifying stability index increased at pH 6 and 9. Oil droplet sizes decreased, while volume frequency distribution of the smaller droplets increased at pH 3 and 6 with the HHP treatment. Emulsion viscosity increased at pH 6 and 9 and pseudo-plastic flow behaviors were not altered for all emulsions produced with HHP-treated SPP. These results suggested that HHP could modify the SPP structure for better emulsifying properties, which could increase the use of SPP emulsion in the food industry.     

Effect of polyphenolic structure and mass ratio on the emulsifying performance and stability of emulsions stabilized by polyphenol-corn amylose complexes

O/W emulsions stabilized by polyphenol/amylose (AM) complexes with several polyphenol/AM mass ratios and different polyphenols (gallic acid (GA), epigallocatechin gallate (EGCG) and tannic acid (TA)) were prepared by a high-intensity ultrasound emulsification technique. The effect of the pyrogallol group number of polyphenols and the mass ratio of polyphenols/AM on polyphenol/AM complexes and emulsions was studied. The soluble and/or insoluble complexes gradually formed upon adding polyphenols into the AM system. However, insoluble complexes were not formed in the GA/AM systems because GA has only one pyrogallol group. In addition, the hydrophobicity of AM could also be improved by forming polyphenol/AM complexes. The emulsion size decreased with increasing pyrogallol group number on the polyphenol molecules at a fixed ratio, and the size could also be controlled by the polyphenol/AM ratio. Moreover, all emulsions presented various degrees of creaming, which was restrained by decreasing emulsion size or the formation of a thick complex network. The complex network was enhanced by increasing the ratio or pyrogallol group number on the polyphenol molecules, which was because the increasing number of complexes was adsorbed onto the interface. Altogether, compared to GA/AM and EGCG/AM, the TA/AM complex emulsifier had the best hydrophobicity and emulsifying properties, and the TA/AM emulsion had the best emulsion stability.     

Laccase cross-linking of sonicated α-Lactalbumin improves physical and oxidative stability of CLA oil in water emulsion

α-lactalbumin was modified by ultrasound (US, 20 kHz, 43 ± 3.4 W/cm⁻²) pre-treatments (0, 15, 30 and 60 min) and laccase cross-linking of sonicated α-lactalbumin was used to evaluate the physical and oxidative stability of conjugated linoleic acid (CLA) emulsions. The emulsions prepared with laccase cross-linking US-α-lactalbumin (α-lactalbumin treated with US pre-treatment) and US-α-lactalbumin were scrutinized for oxidative and physical stability at room temperature for two weeks of storage. Laccase cross-linking US-α-lactalbumin (Lac-US-α-lactalbumin) revealed improved physical stability in comparison with US-α-lactalbumin, specified by droplet size, structural morphology, adsorbed protein, emulsifying properties and creaming index. SDS-PAGE analysis showed that there was formation of polymers in Lac-US-α-lactalbumin emulsion. Surface hydrophobicity of Lac-US-α-lactalbumin was higher than that of US-α-lactalbumin, and gradually enhanced with the increase of ultrasound time. More importantly, the measurements of peroxide values and conjugated dienes were used to study the oxidative stability of the CLA emulsions. The Lac-US-α-lactalbumin emulsion proved to be reducing the synthesis of fatty acid hydroperoxides and less conjugated dienes compared to the native and US-α-lactalbumin emulsions. This study revealed that the combination of US pre-treatment and laccase cross-linking might be an effective technique for the modification of CLA emulsions.     

Synergic effects of ultrasound and ionic liquids on fluconazole emulsion

The aim of this work was to evaluate the influence of US on the properties of the fluconazole emulsions prepared using imidazolium-based ILs ([C_n C₁im]Br). The effects of the preparation method (mechanical stirring or US), US amplitude, alkyl chain length (of [C₁₂C₁im]Br or [C₁₆C₁im]Br), and IL concentration on the physicochemical properties were evaluated. Properties such as droplet size, span index, morphology, viscosity encapsulation efficiency, and drug release profile were determined. The results showed that US-prepared emulsions had a smaller droplet size and smaller polydispersity (Span) than those prepared by mechanical stirring. Additionally, the results showed that emulsions prepared with [C₁₆C₁im]Br and US had spherical shapes and increased stability compared to emulsions prepared by MS, and also depended on the IL concentration. The emulsion prepared by US at 40% amplitude had increased encapsulation efficiency. US provided a decrease in the viscosity of emulsions containing [C₁₂C₁im]Br; however, in general, all emulsions had viscosity close to that of water. Emulsions containing [C₁₆C₁im]Br had the lowest viscosities of all the emulsions. The emulsions containing the IL [C₁₆C₁im]Br had more controlled release and a lower cumulative percentage of drug release. The IL concentration required to prepare these emulsions was lower than the amount of conventional surfactant required, which highlights the potential synergic effects of ILs and US in preparing emulsions of hydrophobic drugs.     

Influence of milk fat globule membrane and milk protein concentrate treated by ultrasound on the structural and emulsifying stability of mimicking human fat emulsions

The primary objective of the present study was to investigate the effectiveness of ultrasonic treatment time on the particle size, molecular weight, microstructure and solubility of milk fat globule membrane (rich in phospholipid, MPL) and milk protein concentrate (MPC). The mimicking human fat emulsions were prepared using modified proteins and compound vegetable oil and the structural, emulsifying properties and encapsulation efficiency of emulsions were evaluated. After ultrasonic treatment, the cavitation caused particle size decreased and structure change of both MPL and MPC, resulting in the enhancement of protein solubility. While, there was no significant change in molecular weight. Modified proteins by ultrasonic may cause a reduction in particle size and an improvement in emulsifying stability and encapsulation efficiency of emulsions. The optimal ultrasonic time to improve functional properties of MPL emulsion and MPC emulsion were 3 min and 6 min, respectively. The emulsifying stability of MPL emulsion was superior to MPC emulsion, which indicated that MPL is more suitable as membrane material to simulate human fat. Therefore, the obtained results can provide basis for quality control of infant formula.     

Study on the emulsification and oxidative stability of ovalbumin-pectin-pumpkin seed oil emulsions using ovalbumin solution prepared by ultrasound

Pumpkin seed oil (PSO), which is a valuable compound with high nutritional value used for the prevention of various chronic diseases, is prone to oxidation. In this work, small and uniform (su) ovalbumin (OVA) and pectin (PEC) were used to stabilize PSO in the form of an emulsion. The results showed that suOVA-PEC-PSO emulsion with a droplet size of 9.82 ± 0.05 μm was successfully self-assembled from PSO, PEC, and suOVA solution (with a droplet size of 230.13 ± 14.10 nm) treated with 300 W ultrasound, owing to the formation of a more stable interfacial film on the surface of droplets. The interfacial, rheological, emulsifying, and antioxidant properties of the suOVA-PES-PSO emulsions were excellent, owing to the synergistic effects between PEC and suOVA solution. Moreover, the physical stability of the suOVA-PEC-PSO emulsions to salt stress, a freeze-thaw cycle, and heat treatment was also increased and the oxidation of linolenic acid was notably delayed. These results have extended the food-related applications of OVA and PSO, and provide a promising foundation for further exploration of the self-assembly of composite emulsions by small and uniform proteins.     

High-intensity ultrasound improves the physical stability of myofibrillar protein emulsion at low ionic strength by destroying and suppressing myosin molecular assembly

The specific molecular behavior of myofibrillar proteins (MPs) in low-salt media limits the development of muscle protein-based emulsions. This study aimed to evaluate the potential of high-intensity ultrasound (HIU; 150, 300, 450, and 600 W) to improve the physical stability of MP emulsion at low ionic strength and decipher the underlying mechanism. According to the physical stability analysis, HIU pretreatment, especially at 450 W power, significantly improved the physical stability of MP emulsions, as evidenced by the reduced particle size, enhanced inter-droplet interactions, and increased uniformity of the droplet size distribution (p < 0.05). The results of interfacial protein composition, Fourier transform infrared spectroscopy analysis, and microscopic morphology observation of the aqueous MP suspension suggested that HIU induced the depolymerization of filamentous myosin polymers and inhibited the subsequent self-assembly behavior. These effects may facilitate protein adsorption and molecular rearrangement at the oil–water interface, forming a complete interfacial layer and, thus, droplet stabilization. Confocal laser scanning microscopy observations further confirmed these results. In conclusion, these findings provide direct evidence for the role of HIU in improving the physical stability of MP emulsions at low ionic strength.