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Local structure of human hair spatially resolved by sub-micron X-ray beam.

Stanić V, Bettini J, Montoro FE, Stein A, Evans-Lutterodt K - Sci Rep (2015)

Bottom Line: We also find that in the cuticle, a key diffraction feature is absent, indicating the presence of the β-keratin rather than that of the α-keratin phase.This is direct structural evidence that the cuticle contains β-keratin sheets.This work highlights the importance of using a sub-micron x-ray beam to unravel the structures of poorly ordered, multi-phase systems.

View Article: PubMed Central - PubMed

Affiliation: Brazilian Synchrotron Light Source, CNPEM, SP 13083-970, Brazil.

ABSTRACT
Human hair has three main regions, the medulla, the cortex, and the cuticle. An existing model for the cortex suggests that the α-keratin- based intermediate filaments (IFs) align with the hair's axis, but are orientationally disordered in-plane. We found that there is a new region in the cortex near the cuticle's boundary in which the IFs are aligned with the hair's axis, but additionally, they are orientationally ordered in-plane due to the presence of the cuticle/hair boundary. Further into the cortex, the IF arrangement becomes disordered, eventually losing all in-plane orientation. We also find that in the cuticle, a key diffraction feature is absent, indicating the presence of the β-keratin rather than that of the α-keratin phase. This is direct structural evidence that the cuticle contains β-keratin sheets. This work highlights the importance of using a sub-micron x-ray beam to unravel the structures of poorly ordered, multi-phase systems.

No MeSH data available.


Related in: MedlinePlus

The SAXS patterns taken on a single hair with the incident X-ray beam ⊥ to the hair axis is shown in (A) to (C). (A) is for the top of the hair in the cuticle, (B) is largely the cortex region and (C) for the bottom edge of the hair in the cuticle region. Corresponding real- space STEM images of hair cut longitudinally are shown in (D) (cuticle) and (E) (cortex) with no staining or coating. In (D), we again observe the intermediate zone. (F) shows SEM images of the hair and the detail of the cuticle shows that the’s scales are oriented with an angular offset with respect to the hair’s axis. The angular offset between the hair’s axis and the cuticle scales in (F) is the same angular offset we observe in reciprocal space between (A,B), or (B,C).
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f3: The SAXS patterns taken on a single hair with the incident X-ray beam ⊥ to the hair axis is shown in (A) to (C). (A) is for the top of the hair in the cuticle, (B) is largely the cortex region and (C) for the bottom edge of the hair in the cuticle region. Corresponding real- space STEM images of hair cut longitudinally are shown in (D) (cuticle) and (E) (cortex) with no staining or coating. In (D), we again observe the intermediate zone. (F) shows SEM images of the hair and the detail of the cuticle shows that the’s scales are oriented with an angular offset with respect to the hair’s axis. The angular offset between the hair’s axis and the cuticle scales in (F) is the same angular offset we observe in reciprocal space between (A,B), or (B,C).

Mentions: To compare with previous publications, we took diffraction images with the beam ⊥ to the hair axis, as depicted in Fig. 3A–C. STEM images of the cortex and cuticle, cut in a longitudinal plane are shown respectively, in Fig. 3D,E. The SAXS from the cortex (Fig. 3B) shows two peaks at ±q0 on an axis that is ⊥ to the direction of the hair’s axis. Relative to this axis, the cuticle peaks that are at the top of the hair (Fig. 3A) and bottom of the hair (Fig. 3B) are offset, respectively, by 4.6 ± 0.1 degrees and −4.5 ± 0.1 degrees. These angular offsets have been correlated with the orientation of the cuticle scales relative to the hair axis, as viewed from the ⊥ direction (SEM image in Fig. 3F). Other than these angular offsets, the layer spacing of the cuticle in Fig. 3A,C are consistent to those observed in Fig. 2B. Clearly, the SAXS data from the and ⊥ directions show (Fig. 1N,A,C) that the cuticle is layered on the 210 Å length-scale, while electron microscopy (Fig. 1L) shows that it is layered on the 5000 Å length scale.


Local structure of human hair spatially resolved by sub-micron X-ray beam.

Stanić V, Bettini J, Montoro FE, Stein A, Evans-Lutterodt K - Sci Rep (2015)

The SAXS patterns taken on a single hair with the incident X-ray beam ⊥ to the hair axis is shown in (A) to (C). (A) is for the top of the hair in the cuticle, (B) is largely the cortex region and (C) for the bottom edge of the hair in the cuticle region. Corresponding real- space STEM images of hair cut longitudinally are shown in (D) (cuticle) and (E) (cortex) with no staining or coating. In (D), we again observe the intermediate zone. (F) shows SEM images of the hair and the detail of the cuticle shows that the’s scales are oriented with an angular offset with respect to the hair’s axis. The angular offset between the hair’s axis and the cuticle scales in (F) is the same angular offset we observe in reciprocal space between (A,B), or (B,C).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4663634&req=5

f3: The SAXS patterns taken on a single hair with the incident X-ray beam ⊥ to the hair axis is shown in (A) to (C). (A) is for the top of the hair in the cuticle, (B) is largely the cortex region and (C) for the bottom edge of the hair in the cuticle region. Corresponding real- space STEM images of hair cut longitudinally are shown in (D) (cuticle) and (E) (cortex) with no staining or coating. In (D), we again observe the intermediate zone. (F) shows SEM images of the hair and the detail of the cuticle shows that the’s scales are oriented with an angular offset with respect to the hair’s axis. The angular offset between the hair’s axis and the cuticle scales in (F) is the same angular offset we observe in reciprocal space between (A,B), or (B,C).
Mentions: To compare with previous publications, we took diffraction images with the beam ⊥ to the hair axis, as depicted in Fig. 3A–C. STEM images of the cortex and cuticle, cut in a longitudinal plane are shown respectively, in Fig. 3D,E. The SAXS from the cortex (Fig. 3B) shows two peaks at ±q0 on an axis that is ⊥ to the direction of the hair’s axis. Relative to this axis, the cuticle peaks that are at the top of the hair (Fig. 3A) and bottom of the hair (Fig. 3B) are offset, respectively, by 4.6 ± 0.1 degrees and −4.5 ± 0.1 degrees. These angular offsets have been correlated with the orientation of the cuticle scales relative to the hair axis, as viewed from the ⊥ direction (SEM image in Fig. 3F). Other than these angular offsets, the layer spacing of the cuticle in Fig. 3A,C are consistent to those observed in Fig. 2B. Clearly, the SAXS data from the and ⊥ directions show (Fig. 1N,A,C) that the cuticle is layered on the 210 Å length-scale, while electron microscopy (Fig. 1L) shows that it is layered on the 5000 Å length scale.

Bottom Line: We also find that in the cuticle, a key diffraction feature is absent, indicating the presence of the β-keratin rather than that of the α-keratin phase.This is direct structural evidence that the cuticle contains β-keratin sheets.This work highlights the importance of using a sub-micron x-ray beam to unravel the structures of poorly ordered, multi-phase systems.

View Article: PubMed Central - PubMed

Affiliation: Brazilian Synchrotron Light Source, CNPEM, SP 13083-970, Brazil.

ABSTRACT
Human hair has three main regions, the medulla, the cortex, and the cuticle. An existing model for the cortex suggests that the α-keratin- based intermediate filaments (IFs) align with the hair's axis, but are orientationally disordered in-plane. We found that there is a new region in the cortex near the cuticle's boundary in which the IFs are aligned with the hair's axis, but additionally, they are orientationally ordered in-plane due to the presence of the cuticle/hair boundary. Further into the cortex, the IF arrangement becomes disordered, eventually losing all in-plane orientation. We also find that in the cuticle, a key diffraction feature is absent, indicating the presence of the β-keratin rather than that of the α-keratin phase. This is direct structural evidence that the cuticle contains β-keratin sheets. This work highlights the importance of using a sub-micron x-ray beam to unravel the structures of poorly ordered, multi-phase systems.

No MeSH data available.


Related in: MedlinePlus