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Croda Europe Ltd, Foundry Lane, Widnes, WA8 8UB, UK.
Int J Cosmet Sci. 2021 Feb;43(1):26-37. doi: 10.1111/ics.12663. Epub 2020 Oct 15.
To investigate the effects of different molecular weight (MW), wool derived hydrolysed keratins (i.e. peptides) on the physical properties of relaxed textured hair.
Very curly hair of African origin was relaxed using sodium hydroxide-based treatment. Relaxed hair was treated with different MW peptides derived from keratin protein and an amino acid, L-Leucine. The low-MW keratin peptides were 221 Da, the mid-MW keratin peptides were approximately 2577 Da, and the high-MW keratin peptides were approximately 75 440 Da. The penetration of these different peptides into relaxed hair was evaluated using a laser scanning micrometre and by fluorescence microscopy. The effect of these compounds on single-fibre mechanical properties and thermal properties was evaluated using tensile and DSC testing, respectively.
Low- and mid-MW compounds were able to penetrate deep into the hair cortex. High-MW peptide adsorbed onto the hair surface and possibly slightly penetrated into the outer layers of the fibre surface. Both mid- and high-MW keratin peptides, increased Young's modulus and reduced hair breakage at 20% and 80% relative humidity. With the exception of mid-MW peptide, other peptides and amino acid were not able to modify thermal properties of relaxed textured hair.
Our data suggest that low-MW compounds may increase hair volume, and high-MW peptides may repair damage on freshly relaxed textured hair.
研究不同分子量（MW）的羊毛角蛋白水解产物（即肽）对松弛处理头发物理性能的影响。
采用氢氧化钠处理，对源自非洲的非常卷曲的头发进行松弛处理。将不同 MW 的角蛋白肽和氨基酸 L-亮氨酸处理松弛的头发。低 MW 角蛋白肽为 221 Da，中 MW 角蛋白肽约为 2577 Da，高 MW 角蛋白肽约为 75440 Da。使用激光扫描显微镜和荧光显微镜评估这些不同肽进入松弛头发的渗透情况。分别使用拉伸和 DSC 测试评估这些化合物对单纤维机械性能和热性能的影响。
低 MW 和中 MW 化合物能够深入头发皮质层。高 MW 肽吸附在头发表面上，可能稍微渗透到纤维表面的外层。中 MW 和高 MW 角蛋白肽均能增加 Young 模量，并减少在 20%和 80%相对湿度下头发的断裂。除了中 MW 肽之外，其他肽和氨基酸都不能改变松弛处理头发的热性能。
我们的数据表明，低 MW 化合物可能会增加头发体积，而高 MW 肽可能会修复新松弛处理头发的损伤。
