大豆硒蛋白构象的光谱法研究

Study on the Conformation of Soybean Selenoprotein Solution with Spectroscopy Methods

采用荧光光谱、紫外光谱并结合红外光谱对比研究了大豆硒蛋白和大豆蛋白的结构区别，并用荧光相图法分析了脲诱导下两种蛋白的去折叠过程。考察了温度、pH 值对大豆硒蛋白质构象的影响，同时对其乳化稳定性能进行了测定。结果表明，与大豆分离蛋白相比，大豆硒蛋白分子中的共价二硫键受到破坏，分子内氢键作用减弱，疏水相互作用增强，蛋白质分子发生伸展。大豆硒蛋白在溶液中只呈现“折叠”和“松散”两种状态，与大豆蛋白相比更容易被水解变性。升高温度，大豆硒蛋白溶液存在明显荧光热猝灭效应，疏水性逐渐增强，蛋白质分子趋于折叠。在 pH 值2.8-8.0的范围内，大豆硒蛋白的 Trp 残基主要分布于其分子外部的极性环境中，并随pH 值变化在等电点两侧呈现不同的构象变化。在酸性环境中大豆硒蛋白较易发生从松散到折叠的构象转变，碱性条件则较有利于大豆硒蛋白以松散的结构存在。此外，基于紫外光谱数据分析了大豆硒蛋白乳化特性，结果表明降低温度有利于增强大豆硒蛋白的乳化性能，但使其稳定性能下降。

The structure characteristic of soybean selenoprotein and soy protein isolate （SPI）were investigated with fluores-cence,ultraviolet and Fourier transform infrared （FTIR）spectrum.The unfolding process of two proteins was analyzed with fluorescence phase diagram method.The stability of emulsion properties and the influence of concentration,temperature and pH on the conformation of soy selenoproteins were also determined.The results indicated that the covalent disulfide bond of soybean selenoprotein molecules was damaged;the hydrogen bonding become weak;the hydrophobic interactions were enhanced and the protein chain molecules were extended.Soybean selenoprotein displayed only“folding”and“loose”state in solution,which illus-trated soybean selenoprotein more tend to hydrolysis when compared with soybean protein.With temperature increasing,the flu-orescence quenching effect occurred and the hydrophobicity of soy selenoproteins was also gradually increased,which reflected the protein molecules tends to be folded.In the range of pH 2.8-8.0,the Trp residue of soybean selenoprotein was mainly dis-tributed in the polarity of the external environment and presented different conformational change on both sides of the isoelectric point under different pH value.In acidic environment,the soybean selenoprotein was easy to appear conformational transition from loose to fold.But it was conducive for soybean selenoprotein to existence in loose structure in alkaline conditions.In addi-tion,the emulsifying properties of soybean selenoprotein were analyzed based on UV spectral data.Results showed that lower temperature helps to enhancement the emulsification but unfavorable the stability of the soybean selenoprotein.