Hair analysis plays an important role in forensic toxicology and biomonitoring tests. However, cosmetic treatments cause changes to the hair. Thus, a better understanding of the hair’s structure and the factors that influence its composition is critical. It is known that oxidative treatments modify the hair chemical, structural and mechanical properties. These treatments also cause degradation of the melanin as well as of the structures present in the hair cuticle and cortex. Considering that the literature is unanimous regarding the increase in hydrophilicity and porosity promoted in human hair by bleaching, in this work we investigated how this oxidative damage is triggered. By combining several techniques, inelastic and quasi-elastic neutron scattering, differential scanning calorimetry, thermal gravimetric analysis and X-ray diffraction, we were able to connect the chemical and structural changes to a subtle dynamic modification of the proton mobility in the hair fibers. In addition, alterations in the thermal behavior evidenced a small denaturation of α-keratin intermediate filaments and a slight decrease in the amount of confined water in the hair fibers. Moreover, data obtained by neutron spectroscopy indicated that bleaching attacks the thioester groups of the proteins causing larger proton mobility of the hydrogenous components (water, protein and/or lipids).

头发分析在法医毒理学和生物监测测试中起着重要作用。但是，美容治疗会使头发发生变化。因此，更好地了解头发的结构以及影响其组成的因素至关重要。众所周知，氧化处理会改变头发的化学，结构和机械性能。这些处理还导致黑色素以及毛发表皮和皮质中存在的结构的降解。考虑到文献对于通过漂白促进人发中亲水性和孔隙率增加的观点是一致的，在这项工作中，我们研究了这种氧化损伤是如何引发的。通过结合非弹性和准弹性中子散射，差示扫描量热法，热重分析和X射线衍射等多种技术，我们能够将化学和结构变化与头发纤维中质子迁移率的微妙动态变化联系起来。此外，热行为的变化表明，其小变性α-角蛋白中间丝和头发纤维中的水分含量略有下降。此外，通过中子光谱法获得的数据表明，漂白作用攻击蛋白质的硫酯基团，导致氢组分（水，蛋白质和/或脂质）的质子迁移率更大。