School of Materials, University of Manchester, Manchester M60 1QD, UK.
Langmuir. 2010 May 18;26(10):7365-9. doi: 10.1021/la9043842.
The natural surface of human hair (epicuticle) consists of a bilayer of heavily cross-linked proteins toward the individual cuticle cell inside combined with a monomolecular, hydrophobic layer of mixed fatty acids to the outside (F-layer), which is generally assumed to be homogeneous. Wetting force profiles along segments of hair from female test persons with lengths equivalent to about 1 month of growth (approximately 10 mm) are presented. In a multistep analysis, applying curve smoothing as well as Fourier and principal components analysis, for hair lengths comprising daily and weekly growth (2 mm) pronounced systematic changes are observed in the profiles, which show that the wettability curves are nonstochastic in nature and that hair exhibits a strongly nonhomogeneous surface. Specifically, a compound daily rhythm is observed for wettability, which through its typical bimodality can be linked to continuous changes of the hair surface during wake and sleep phases. The data set furthermore suggests systematic monthly changes, which may be related to the menstrual cycle. In consequence, the results not only provide proof for the inhomogeneity of the immediate hair surface but also lead to the hypothesis that it preserves a rather detailed and long-term, individual chronobiological record, through a specific, spatially modulated distribution of hydrophobic (lipids) and hydrophilic (proteins) regions, "written" by the composition of the cell membrane of the cuticle cell prior to apoptosis.
人类头发的天然表面（表皮层）由两层交联紧密的蛋白质组成，这些蛋白质位于单个角质细胞内部，与外部的混合脂肪酸单分子疏水性层（F 层）结合在一起，通常认为 F 层是均匀的。本文呈现了来自女性测试对象的头发片段在润湿力方面的特征，这些头发的长度相当于大约 1 个月的生长（约 10 毫米）。在一个多步骤的分析中，应用曲线平滑以及傅里叶和主成分分析，对于包括每日和每周生长（2 毫米）的头发长度，在这些特征中观察到了明显的系统变化，表明润湿性曲线本质上是非随机的，并且头发具有强烈的非均匀表面。具体来说，观察到了润湿性的复合日周期，通过其典型的双峰性，可以将其与清醒和睡眠阶段头发表面的连续变化联系起来。该数据集还表明存在系统的月度变化，这可能与月经周期有关。因此，这些结果不仅提供了头发表面不均匀性的证据，而且还提出了一个假设，即通过角质细胞细胞膜组成的特定、空间调制的疏水区（脂质）和亲水区（蛋白质）的分布，在凋亡之前“书写”了一个相当详细和长期的个体生物钟记录，从而保留了一个相当详细和长期的个体生物钟记录。
