羟基自由基氧化对乌贼蛋白分子间作用力及结构的影响

为研究贮藏过程中蛋白质氧化对蛋白质分子间作用力的影响机理,通过建立羟基自由基(·OH)氧化体系体外模拟乌贼肉在冻藏过程中蛋白质氧化的过程,从而探究蛋白质分子间作用力与结构的变化情况。结果表明,随着·OH氧化体系中H₂O₂浓度的增加,乌贼肌原纤维蛋白分子间作用力平衡被打破,离子键和氢键含量逐渐降低,疏水作用力逐渐增强,二硫键和非二硫共价键含量逐渐增加;肌原纤维蛋白表面疏水性逐渐增加;巯基与活性巯基含量逐渐降低。应用红外光谱(FTIR)分析氧化过程中蛋白质二级结构的变化规律,结果表明,自由基对氨基酸侧链和蛋白肽链进行了攻击,随着H₂O₂浓度的增加,光谱带向不同波数方向有规律地移动,蛋白质二级结构发生变化,α-螺旋和β-折叠含量降低,β-转角和无规则卷曲含量增加。石蜡切片显示,随着H₂O₂浓度的增加,肌纤维蛋白结构趋于疏松、间隙持续增大、肌丝变细且断裂卷曲量增多。本研究为探究乌贼肉蛋白质氧化的机理提供了理论依据,为延长乌贼贮藏期、提高经济效益与食用品质等相关研究奠定了理论基础。

Effect of Hydroxyl Radical Oxidation on Myofibrillar Protein Intermolecular Force and Structural of Sepia esculenta

In order to explore the influence mechanism of protein oxidation on the intermolecular interaction between proteins during storage, the hydroxyl free radical oxidation system was established to simulate the protein oxidation process of sepia esculenta in vitro during freezing storage, the changes of intermolecular forces and protein structures were investigated. The results showed that the balance of intermolecular force between the myofibrillar protein was broken with the increase of H₂O₂ concentration in the hydroxyl radical oxidation system, the content of ionic bond and hydrogen bond significantly reduced (P<0.05), while the hydrophobic interaction force, disulfide bond and non-disulfide covalent bond increased (P<0.05). As well as the surface hydrophobicity of myofibrillar protein (P<0.05). Both sulfhydryl and reactive thiol content decreased significantly (P<0.05). The changes of the secondary structures of myofibrillar protein were analyzed by Infrared spectroscopy (FTIR), which indicated that the amino acid side chain and the peptide chain were attacked by hydroxyl radicals. The spectral band shifted to different wavelength regularly along with the increase of H₂O₂ concentration, the content of α-helix and β-sheet decreased, while the β-turn and random curl content tended to increase. Paraffin section showed that the higher of oxidation degree, the structure of myofibrils protein tended to be loose, the gap increased continually, and the muscle filament became thinner and tended to fracture and curl seriously. This study provided theoretical evidence for exploring the mechanism of protein oxidation in sepia esculenta, and built the foundation for prolonging the shelf life, improving economic efficiency and eating quality.