鸡蛋卵转铁蛋白铁结合能力及性质的研究

Analysis of the Iron-binding Capacity and Characteristics of Hen Egg Ovotransferrin under Different Conditions

本试验研究了鸡蛋卵转铁蛋白与不同浓度铁离子的结合能力,以及卵转铁蛋白在不同p H值和Na HCO3条件下与铁离子的结合能力;采用差示扫描量热仪(DSC)和圆二色性(CD)光谱分析卵转铁蛋白铁饱和度对其热变性温度和结构的影响。结果表明,铁离子与卵转铁蛋白的摩尔比值在2.2左右时,卵转铁蛋白铁达到完全饱和;在中性和偏碱性的条件下,卵转铁蛋白对铁结合能力比较高;卵转铁蛋白铁结合能力随着Na HCO3浓度的增加而增强,当其浓度超过75 mmol/L以后,铁结合能力基本保持不变。卵转铁蛋白铁饱和度越高,其热变性温度越高,由去铁卵转铁蛋白的63.41℃到饱和铁卵转铁蛋白的83.29℃;去铁卵转铁蛋白比饱和铁卵转铁蛋白的远紫外CD光谱带更加趋于负值,α-螺旋含量有微小的减少,减少量为4.40%,而β-折叠、β-转角和其它的含量均有所增加,增加量分别:2.80%、1.20%、12.90%;在近紫外CD光谱区,饱和铁卵转铁蛋白的三级结构发生了较为明显的变化。

The binding capacity of hen egg ovotransferrin(OVT) to different concentrations of iron ions was studied under multiple p H conditions and Na HCO3 concentrations. The effects of iron saturation on the thermal denaturation temperature and structure of OVT were analyzed by differential scanning calorimetry(DSC) and circular dichroism(CD) spectrum analysis. The results showed that complete iron saturation was obtained at an approximate iron ion to OVT molar ratio of 2.2. OVT exhibited higher iron-binding capacity under neutral or slightly alkaline p H conditions. The iron-binding capacity of OVT also increased with the increase in Na HCO3 concentration; however, a steady-state level was reached at Na HCO3 concentrations exceeding 75 mmol/L. The thermal denaturation temperature of OVT increased corresponding to the increase in iron saturation, and was observed to be 63.41 ℃ and 83.29 ℃ for apo-ovotransferrin(apo-OVT) and holo-ovotransferrin(holo-OVT), respectively. Apo-OVT showed a more negative band in the far-ultraviolet CD spectrum compared to holo-OVT; the α-helical content of apo-OVT decreased by 4.4%, while that of β-sheet strands, β-turns, and other structures increased by 2.80%, 1.20%, and 12.90%, respectively. The tertiary structure of holo-OVT displayed an obvious change in the near-ultraviolet region of the CD spectrum.