“…Under the extension stress, Caucasian hair cuticles collapse to form small fragments while Asian hair cuticles fail as large pieces . When the keratin fibers are treated by chemical process, such as stretching, waving, and bleaching, the crosslinking of disulfide bond can be weakened or destroyed and caused the transformation of α‐helix→β‐pleated sheet . Meanwhile, the disulfide bond is oxidized into new cystine oxidation .…”
“…Under the extension stress, Caucasian hair cuticles collapse to form small fragments while Asian hair cuticles fail as large pieces . When the keratin fibers are treated by chemical process, such as stretching, waving, and bleaching, the crosslinking of disulfide bond can be weakened or destroyed and caused the transformation of α‐helix→β‐pleated sheet . Meanwhile, the disulfide bond is oxidized into new cystine oxidation .…”
“…The peaks at ∼1515 cm −1 and ∼1635 cm −1 correspond to the amide II and amide I region, respectively. 40 Due to these spectral differences, the synthetic hair spectrum can be visually differentiated from spectra of natural hair quite easily and, therefore, no advanced statistical modeling was necessary. Figure 1.The raw mean spectra of synthetic, human, cat, and dog hair samples.…”
Section: Resultsmentioning
confidence: 99%
“…The prominent features of an IR spectrum of natural hair correspond to specific vibrational modes of the amino acids and lipids present. 39 The averaged raw spectra for human, cat, dog, and synthetic hair, as shown in Figure 1, reveal visual differences between natural hair and synthetic hair spectra. These spectral differences include the absence of the amide A peak at 3300 cm À1 and the more intense CH 3 / CH 2 (alkane stretching) peak at 2950 cm À1 in the averaged synthetic hair fiber spectrum.…”
Section: Natural Hair Versus Synthetic Hairmentioning
Hair and fibers are common forms of trace evidence found at crime scenes. The current methodology of microscopic examination of potential hair evidence is absent of statistical measures of performance, and examiner results for identification can be subjective. Here, attenuated total reflection (ATR) Fourier transform-infrared (FT-IR) spectroscopy was used to analyze synthetic fibers and natural hairs of human, cat, and dog origin. Chemometric analysis was used to differentiate hair spectra from the three different species, and to predict unknown hairs to their proper species class, with a high degree of certainty. A species-specific partial least squares discriminant analysis (PLSDA) model was constructed to discriminate human hair from cat and dog hairs. This model was successful in distinguishing between the three classes and, more importantly, all human samples were correctly predicted as human. An external validation resulted in zero false positive and false negative assignments for the human class. From a forensic perspective, this technique would be complementary to microscopic hair examination, and in no way replace it. As such, this methodology is able to provide a statistical measure of confidence to the identification of a sample of human, cat, and dog hair, which was called for in the 2009 National Academy of Sciences report. More importantly, this approach is non-destructive, rapid, can provide reliable results, and requires no sample preparation, making it of ample importance to the field of forensic science.
“…This is because the untreated fibers hair showed only the band around 1235 cm ‐1 related to β‐sheet. In this way, it can be suggested that this last conformation dominated the structure of the cuticle and it was shown to be less ordered, that is, amorphous, as opposed to the underlying cortex; Increase in the band intensity around 803 cm ‐1 which is related to out‐of‐plane deformation in NH 2 . According to Mujeeb & Zafar, from 800 until 600 cm ‐1 related to cis–double bond (=CH), N–H wagging, CO 2 absorption and ions and NH 2.…”
Section: Discussionmentioning
confidence: 98%
“…This is because the untreated fibers hair showed only the band around 1235 cm -1 related to β-sheet. In this way, it can be suggested that this last conformation dominated the structure of the cuticle and it was shown to be less ordered, that is, amorphous, as opposed to the underlying cortex 23…”
Summary
Background
Hair‐straightening treatments may involve the use of thermal devices, which potentially cause damages in the cuticle and cortex of the hair fibers. Particularly, the heat causes denaturation of the α‐keratin and the degradation of the components of the hair cortex.
Objectives
The aim of this study was to evaluate the effect of heating on the cuticle and cortex of the Caucasian and Asian virgin hair by using heat iron flat.
Methods
The effects of the heating in the tresses of Caucasian and Asian virgin hair were analyzed by thermogravimetry/differential scanning calorimetry‐Fourier transform infrared/mass spectrometry (TG/DSC‐MS/FTIR), protein loss analysis (PLA), Fourier transform infrared (FTIR‐ATR), and scanning electron microscope (SEM).
Results
TG/DSC‐MS/FTIR results were: formation of the H2O between 25‐170°C and CO2, SCO and H2S from 200°C. Denaturation temperature = 237°C. Protein loss: Asian hair>Caucasian hair. Data presented statistically significant alterations, α = 5, P ≤ 0.05, n = 3. FTIR‐ATR: changes in the secondary structural conformation of the protein of hair cuticle. SEM: heat caused damage to hair cuticle.
Conclusions
The results evidenced the importance of the control of temperature in the procedures involving heat. The damage caused by thermal devices showed be dependent of the ethnicity analyzed (Caucasian and Asian hair).
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