Atomic force microscopy integrated with infrared spectroscopy (AFM-IR) has been used to topographically and chemically examine the medulla of human hair fibres with nanometre scale lateral resolution. The mapping of cross-sections of the medulla showed two distinct structural components which were subsequently characterised spectroscopically. One of these components was shown to be closely similar to cortical cell species, consistent with the fibrillar structures found in previous electron microscope (EM) investigations. The other component showed large chemical differences from cortical cells and was assigned to globular vacuole species, also confirming EM observations. Further characterisation of the two components was achieved through spectral deconvolution of the protein Amide-I and -II bands. This showed that the vacuoles have a greater proportion of the most thermodynamically stable conformation, namely the antiparallel β-sheet structures. This chimes with the observed lower cysteine concentration, indicating a lower proportion of restrictive disulphide cross-link bonding. Furthermore, the large α-helix presence within the vacuoles points to a loss of matrix-like material as well as significant intermolecular stabilisation of the protein structures. By analysing the carbonyl stretching region, it was established that the fibrillar, cortical cell-like components showed considerable stabilisation from H-bonding interactions, similar to the cortex, involving amino acid side chains whereas, in contrast, the vacuoles were found to only be stabilised significantly by structural lipids.

中文翻译：

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使用混合原子力显微镜和红外光谱 (AFM-IR) 在纳米尺度上识别头发髓质的化学成分

结合红外光谱 (AFM-IR) 的原子力显微镜已用于以纳米级横向分辨率对人类头发纤维的髓质进行地形学和化学检查。髓质横截面的映射显示了两个不同的结构成分，随后在光谱上对其进行了表征。其中一种成分被证明与皮层细胞种类非常相似，这与之前的电子显微镜 (EM) 研究中发现的纤维状结构一致。另一个成分显示出与皮层细胞的巨大化学差异，并被分配到球状液泡物种中，这也证实了 EM 观察结果。通过蛋白质 Amide-I 和 -II 条带的光谱反卷积来进一步表征这两种成分。这表明液泡具有更大比例的最热力学稳定的构象，即反平行的β-折叠结构。这与观察到的较低半胱氨酸浓度相吻合，表明限制性二硫键交联键的比例较低。此外，液泡内存在大的α-螺旋表明基质样物质的损失以及蛋白质结构的显着分子间稳定性。通过分析羰基拉伸区域，确定纤维状的皮质细胞样成分在 H 键相互作用中表现出相当大的稳定性，类似于皮质，涉及氨基酸侧链，而相反，液泡被发现仅是结构脂质显着稳定。即反平行的β-折叠结构。这与观察到的较低半胱氨酸浓度相吻合，表明限制性二硫键交联键的比例较低。此外，液泡内存在大的α-螺旋表明基质样物质的损失以及蛋白质结构的显着分子间稳定性。通过分析羰基拉伸区域，确定纤维状的皮质细胞样成分在 H 键相互作用中表现出相当大的稳定性，类似于皮质，涉及氨基酸侧链，而相反，液泡被发现仅是结构脂质显着稳定。即反平行的β-折叠结构。这与观察到的较低半胱氨酸浓度相吻合，表明限制性二硫键交联键的比例较低。此外，液泡内存在大的α-螺旋表明基质样物质的损失以及蛋白质结构的显着分子间稳定性。通过分析羰基拉伸区域，确定纤维状的皮质细胞样成分在 H 键相互作用中表现出相当大的稳定性，类似于皮质，涉及氨基酸侧链，而相反，液泡被发现仅是结构脂质显着稳定。表明限制性二硫化物交联键的比例较低。此外，液泡内存在大的α-螺旋表明基质样物质的损失以及蛋白质结构的显着分子间稳定性。通过分析羰基拉伸区域，确定纤维状的皮质细胞样成分在 H 键相互作用中表现出相当大的稳定性，类似于皮质，涉及氨基酸侧链，而相反，液泡被发现仅是结构脂质显着稳定。表明限制性二硫化物交联键的比例较低。此外，液泡内存在大的α-螺旋表明基质样物质的损失以及蛋白质结构的显着分子间稳定性。通过分析羰基拉伸区域，确定纤维状的皮质细胞样成分在 H 键相互作用中表现出相当大的稳定性，类似于皮质，涉及氨基酸侧链，而相反，液泡被发现仅是结构脂质显着稳定。