Phycoerythrin (PE) is a natural water-soluble pigment protein with characteristic phycobilins and is sensitive to thermal and light environmental changes. In this study, PE was extracted from Porphyra haitanensis and PE–oligochitosan complexes (POC) were fabricated by a self-assembly approach. The effects of cationic oligochitosan on the binding interaction, structure, size distribution, and color stability of PE were evaluated. The stoichiometric number n was calculated to be 21.67 ± 2.65 (oligochitosan/PE) and the binding constant K was (6.47 ± 0.48) × 10⁵ M^–1. Cationic oligochitosan could electrostatically interact with PE and affect the PE structure by increasing the α-helix content. In addition, high concentrations of oligochitosan led to the formation of dense phycoerythrin protein granules. Moreover, at a reaction ratio of 20.0:1 (oligochitosan/PE), being approximately the predicted stoichiometric number n, the thermal stability (40–80 °C), natural light stability, and ultraviolet light irradiation (254 nm) stability of the POC were improved. This study provides an approach to reduce the susceptibility of PE upon environmental changes by forming a stable self-assembly complex, which will promote the application of PE as a natural pigment protein in food and chemical applications.

中文翻译：

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通过静电相互作用自组装藻红蛋白与壳寡糖以稳定藻红蛋白

藻红蛋白 (PE) 是一种天然水溶性色素蛋白，具有特征性藻胆素，对热和光环境变化敏感。在这项研究中，PE 是从紫菜中提取的，PE-低聚壳聚糖复合物（POC）是通过自组装方法制造的。评估了阳离子壳聚糖对 PE 的结合相互作用、结构、尺寸分布和颜色稳定性的影响。计算出的化学计量数n为 21.67 ± 2.65（壳寡糖/PE），结合常数 K 为 (6.47 ± 0.48) × 10 ⁵ M ^–1. 阳离子低聚壳聚糖可以与 PE 发生静电相互作用，并通过增加 α-螺旋含量来影响 PE 结构。此外，高浓度的低聚壳聚糖导致形成致密的藻红蛋白颗粒。此外，在 20.0:1（壳寡糖/PE）的反应比下，大约是预测的化学计量数n、热稳定性（40-80 °C）、自然光稳定性和紫外光照射（254 nm）稳定性POC 进行了改进。该研究提供了一种通过形成稳定的自组装复合物来降低 PE 对环境变化的敏感性的方法，这将促进 PE 作为天然色素蛋白在食品和化学应用中的应用。