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

Abstract

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.

Towards Fingermark Dating: A Raman Spectroscopy Proof‐of‐Concept Study

“…The former two bands were assigned to α‐helix and β‐sheet, respectively, whereas the 1620 cm −1 shoulder was attributed to Phe, Tyr, and Trp amino acids. Recently, when keratin from hair with high glycine–tyrosine content was studied, a distinct peak at 1614 cm −1 was ascribed to aromatic amino acids. In our study (for particles), a second peak separated from the amide I band was observed in this region centered at 1605 cm −1 (Figures A and S10–S12).…”

“…For example, it is known that side chains of protein amino acids are oxidized, by varying mechanisms, to undergo protein carbonylation accompanied with structural changes to cause oxidative stress and diseases . Thus, the elevated peak at approximately 1630 cm −1 (Figures C and B) might be an effect of increased (parallel) β‐sheet structure and/or of oxidative forms of amino acid side chains in aged FMs. Laser‐induced fluorescence (LIF) measurements similar to the van Dam et al.…”

Conformation changes in human hair keratin observed using confocal Raman spectroscopy after active ingredient application

“…Several physical and biochemical techniques have already been used to test human hair and characterise keratin fibres, such as x‐ray diffraction, solid state nuclear magnetic resonance (NMR), circular dichroism, scanning electron microscopy and high‐pressure liquid chromatography–mass spectrometry (HPLC–MS) . Although biochemical and microscopic techniques are innovative, they present some technical limitations owing to protocol complexities, prior sample preparation, the need for extraction, and reagent costs.…”

Human hair keratin and its interaction with metal ions

“…It is well known that KAP acts as a crosslinker with KIF to form disulfide bonds and this is the main mechanism that holds the cortical region together [23]. Although many KAP had been discovered and isolated, their properties are still being investigated [29]. [29].…”

“…Although many KAP had been discovered and isolated, their properties are still being investigated [29]. [29]. Hence, it would be interesting to find out the correlation between cysteine in KAP and its interaction with metal ions as well as its behavior compared against KIF.…”