Structure and Performance of Cuticles Isolated from Wool Fibers Using Different Approaches

ABSTRACT

Wool cuticles have a complex hierarchical structure and inherent resistance to general chemicals and enzymes. However, data on the structure and properties of the cuticle, which informs its processing and utilization remains scant. In this paper, we successfully isolated flaky cuticles using the ultrasonic technique from wool residues after keratin extraction with combined L-cysteine and urea (Cuticle-L + U). We then characterized and analyzed the chemical structure and thermal stability of the cuticle-L + U and compared it with the raw wool and wool cuticle isolated with the formic acid method (cuticle-FA). Our data show that the cuticle-L + U has a lower disulfide bond content compared to either raw wool or cuticle-FA. The solid-state ¹³C NMR spectra demonstrated that the raw wool had a higher content of α-helix structures (61.57%), while cuticle-FA (80.08%) and cuticle-L + U (52.32%) had more β-sheet or disorder structures. Differential scanning calorimetry (DSC) analysis indicated that both the cuticle-L + U and cuticle-FA have lower α-helical crystallinity compared to the raw wool, which further proved that the cuticle mainly consists of β-sheet and random coil structure. In addition, TG analysis and SDS-PAGE showed higher thermal stability and insolubility with the cuticle-L + U compared with cuticle-FA.

摘要

羊毛表皮具有复杂的层次结构和对一般化学物质和酶的固有抗性. 然而，关于表皮结构和性质的数据仍然很少，而这些结构和性质决定了表皮的加工和利用. 在本论文中，我们利用超声波技术成功地从角蛋白提取后的羊毛残渣中分离出片状的角质层，并结合L-半胱氨酸和尿素（角质层-L+U）. 然后，我们对角质层-L+U的化学结构和热稳定性进行了表征和分析，并将其与原毛和用甲酸法分离的羊毛角质层（角质层FA）进行了比较. 我们的数据表明，与原毛和角质层FA相比，角质层-L+U的二硫键含量较低. 固体13C NMR谱表明，原毛具有较高的α-螺旋结构（61.57%），而角质层FA（80.08%）和角质层L+U（52.32%）具有较多的β-片状或无序结构. 差示扫描量热（DSC）分析表明，与原毛相比，角质层-L+U和角质层FA的α-螺旋结晶度较低，进一步证明角质层主要由β-片状和无规卷曲结构组成. 此外，TG分析和SDS-PAGE显示，与角质层FA相比，角质层L+U具有更高的热稳定性和不溶性.

KEYWORDS:

• Wool fibers
• cuticle isolation
• keratin
• l-cysteine
• secondary structure
• thermal stability

关键词:

• 羊毛纤维、
• 角质层分离、
• 角蛋白
• L-半胱氨酸、
• 二级结构、
• 热稳定性

Acknowledgments

This work was financially supported by the National Natural Science Foundation of China (No. 51673087), the Graduate student innovation project (KYCX17_1452) and 111 Project (B17021), and the International Joint Research Laboratory for Eco-Textile Technology at Jiangnan University.

Additional information

Funding

This work was supported by the the National Natural Science Foundation of China [51673087]; the Graduate student innovation project [KYCX17_1452]; and  the International Joint Research Laboratory for Eco-Textile Technology at Jiangnan University. .