The effects of esterification on the humidity-dependent glass transition of human hair

Jinks, I; Paul, Prem K. C.; Wortmann, Franz

doi:10.1016/j.tca.2015.06.002

Cited by 6 publications

(9 citation statements)

References 25 publications

(46 reference statements)

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“…To our knowledge, there is no literature study report the precise determination of how the glass transition temperature varies with hydration for SC keratin. However, it has been demonstrated for both hair and wool keratin that upon hydration the glass transition temperature reduced dramatically 59 , 60 , implying the possibility of hydration-induced transition at physiological temperatures. In general, an increase in water activity can lead to phase transitions analogous to temperature-induced transitions for many self-assembled systems composed of, for example, proteins, lipids and surfactants 58 , 61 – 64 .…”

Section: Resultsmentioning

confidence: 99%

Skin hydration: interplay between molecular dynamics, structure and water uptake in the stratum corneum

Mojumdar

Pham

Topgaard

et al. 2017

Sci Rep

110

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Hydration is a key aspect of the skin that influences its physical and mechanical properties. Here, we investigate the interplay between molecular and macroscopic properties of the outer skin layer – the stratum corneum (SC) and how this varies with hydration. It is shown that hydration leads to changes in the molecular arrangement of the peptides in the keratin filaments as well as dynamics of C-H bond reorientation of amino acids in the protruding terminals of keratin protein within the SC. The changes in molecular structure and dynamics occur at a threshold hydration corresponding to ca. 85% relative humidity (RH). The abrupt changes in SC molecular properties coincide with changes in SC macroscopic swelling properties as well as mechanical properties in the SC. The flexible terminals at the solid keratin filaments can be compared to flexible polymer brushes in colloidal systems, creating long-range repulsion and extensive swelling in water. We further show that the addition of urea to the SC at reduced RH leads to similar molecular and macroscopic responses as the increase in RH for SC without urea. The findings provide new molecular insights to deepen the understanding of how intermediate filament organization responds to changes in the surrounding environment.

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Section: Resultsmentioning

confidence: 99%

Skin hydration: interplay between molecular dynamics, structure and water uptake in the stratum corneum

Mojumdar

Pham

Topgaard

et al. 2017

Sci Rep

110

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“…HGT proteins are present in different amounts in different keratinous substrates, giving rise to the observed differences in mechanical and physical properties of different keratinous materials. 10 This has led to the postulation of the internal plasticization theory [11][12] that states that the presence of differing amounts of hydrophobic HGT proteins in keratin substrates is responsible for the different glass transitions exhibited by these materials, and consequently their different physical and mechanical properties. As HGT proteins are in the amorphous matrix of keratin substrates that embed the IFs, This journal is © The Royal Society of Chemistry 20xx…”

Section: Introductionmentioning

confidence: 99%

Molecular modeling and structural characterization of a high glycine–tyrosine hair keratin associated protein

Singh

Palmer

Pudney

et al. 2017

Phys. Chem. Chem. Phys.

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High glycine-tyrosine (HGT) proteins are an important constituent of the keratin associated proteins (KAPs) present in human hair. The glassy state physics of hair fibres are thought to be largely regulated by KAPs, which exist in an amorphous state and are readily affected by environmental conditions. However, there are no studies characterizing the individual KAPs. In this paper, we present the first step to fill this gap by computational modeling and experimental studies on a HGT protein, KAP8.1. In particular, we have modeled the three-dimensional structure of this 63-residue protein using homology information from an anti-freeze protein in snow flea. The model for KAP8.1 is characterized by four strands of poly-proline II (or PPII) type helical secondary structures, held together by two cysteine disulphide bridges. Computer simulations confirm the stability of the modelled structure and show that the protein largely samples the PPII and β-sheet conformations during the molecular dynamics simulations. Spectroscopic studies including Raman, IR and vibrational circular dichroism have also been performed on synthesized KAP8.1. The experimental studies suggest that KAP8.1 is characterised by β-sheet and PPII structures, largely consistent with the simulation studies. The model built in this work is a good starting point for further simulations to study in greater depth the glassy state physics of hair, including its water sorption isotherms, glass transition, and the effect of HGT proteins on KAP matrix plasticization. These results are a significant step towards our goal of understanding how the properties of hair can be affected and manipulated under different environmental conditions of temperature, humidity, ageing and small molecule additives.

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“…At this stage, as the shifts up and down are within 10% units of RH, it is still difficult to state categorically that these chemical treatments, apart from creating absorption sites, as noticeable for bleached hair, can modify glass transition in a defined way. These results do, however, suggest that more experimental work should be undertaken in order to better understand how perming and bleaching chemical treatments can be associated with defined changes in the glass transition in hair, in the way that the esterification of hair has been shown to be [32].…”

Section: Resultsmentioning

confidence: 99%

Learning from hair moisture sorption and hysteresis

Breakspear

Frueh

Neu

et al. 2022

Intern J of Cosmetic Sci

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Objective The process of moisture sorption and desorption by human hair was analysed for extracting hints on the hair structure. Methods The isotherms of moisture sorption and desorption by hair were recorded for untreated and chemically treated (permed and bleached) hair. Data of swelling were also considered. Results By examining the swelling and moisture sorption of keratin fibres, it is possible to conclude that hysteresis is quite improbably caused by capillary condensation. The mobility of the protein chains and the strength of the bonds binding water molecules to the active sites inside the matrix are proposed as causes instead. The concept of “breaking symmetry”, derived from moisture sorption– desorption data, and the method of evaluating this parameter, is proposed as a way of characterizing the chemical treatment of hair. The results show that bleaching produces a larger breaking of symmetry than perming, and this is suggested to be due to new hydrogen bonds, created as a result of the chemical treatment, replacing the original disulphide bonds, which are of different strength compared to the bonds of untreated hair. The quantitative sorption data matched well to the model of grains of matrix enveloped in layers of water molecules at increasing relative humidity, up to 100%. The analysis suggested that, aside from the glass transition event occurring at around 60%–70% relative humidity, there is another, less examined, transition occurring at around 30% relative humidity, assigned to the opening of the hair inner structure, and accommodation of more water molecules. Both transitions are reflected by corresponding changes in the fibre mechanical behaviour. Conclusion The moisture sorption–desorption by hair was shown to not only allow a quantitative differentiation among various cosmetic treatments of the hair but to also provide valuable information on the structure of the fibre.

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The effects of esterification on the humidity-dependent glass transition of human hair

Cited by 6 publications

References 25 publications

Skin hydration: interplay between molecular dynamics, structure and water uptake in the stratum corneum

Skin hydration: interplay between molecular dynamics, structure and water uptake in the stratum corneum

Molecular modeling and structural characterization of a high glycine–tyrosine hair keratin associated protein

Learning from hair moisture sorption and hysteresis

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