天然和热变性乳铁蛋白与α-乳白蛋白聚集体的超分子结构表征

本文在pH6.5磷酸盐缓冲溶液中研究了热变性前后牛乳铁蛋白(bovine lactoferrin,LF)和α-乳白蛋白(α-lactalbumin,ALA)之间的自组装行为。采用ζ-电位、浊度法、动态光散射、光学显微镜、荧光光谱和红外色谱等方法进行表征。结果表明,与天然LF和ALA自组装复合物相比,热变性LF和ALA自组装复合物的ζ-电位较低。天然LF与ALA可以自组装可形成纳米颗粒,粒径最大为(35.24±0.82) nm;经过热变性的LF与ALA自组装形成超分子结构,通过调整ALA浓度,可以得到亚微米和微米颗粒,颗粒粒径最大为(4.11±0.14) μm。天然LF与ALA的复合物均为球状聚集体,分布均一;而热变性LF与ALA的复合物则为网状聚集体,分布不均一。ALA的添加增强了LF中色氨酸残基的疏水性。LF中的C=O和C-N基团均参与了与ALA_{25 ℃}的相互作用。本研究为构建新型双蛋白自组装体及理解双蛋白组装机制提供了理论依据。

Supramolecular Structure Characteristics of Natural and Thermal Modification Lactoferrin-α-Lactalbumin Aggregates

The interaction between natural and thermally modified bovine lactoferrin (LF) and α-lactalbumin (ALA) was investigated at pH6.5 in phosphate buffer. ζ-potential, turbidimetric method, dynamic light scattering, optical microscopy, fluorescence spectrum and infrared chromatography were used for characterization. The results showed that the ζ-potential values of thermally modified LF-ALA complexes were lower than that of natural LF-ALA complexes. Natural LF and ALA could self assemble to form nanoparticles with a maximum size of (35.24±0.82) nm. The thermally modified LF and ALA could self assemble to form supramolecular structure. By adjusting the concentration of ALA, submicrometer and micrometer particles could be obtained. The maximum particle size was (4.11±0.14) μm. The complexes of natural LF and ALA were spherical aggregates with uniform distribution, while the complexes of the thermally modified LF and ALA were large aggregates with uneven distribution. ALA enhanced the hydrophobicity of tryptophan residues in LF. ALA_25℃interacted with the C=O and C-N groups in the LF structural subunits. This study provides a theoretical basis for the construction of novel double protein self-assembly and understanding of the mechanism of double protein assembly.