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Biophysical journal2004; 87(1); 640-647; doi: 10.1529/biophysj.103.036749

New aspects of the alpha-helix to beta-sheet transition in stretched hard alpha-keratin fibers.

Abstract: The putative transformation of alpha-helices into beta-sheets has been studied for more than 50 years in the case of hard alpha-keratin. In a previous study of stretched keratin fibers, we specified the conditions for beta-sheet appearance within horsehair: the formation of beta-sheets requires at least 30% relative humidity. However, this phenomenon was observed in the whole tissue. Then there was no clear chemical identification of the beta-sheets (keratin or matrix proteins) and the exact location of the beta-sheets across the fiber could not be specified. In this study, using wide-angle x-ray scattering and high spatial resolution infrared microspectroscopy, we could determine and characterize the structural elements across hair sections stretched in water, which provides new information about the aforementioned transition. Our results show that the process can be split into three steps: 1), unraveling of the alpha-helical coiled-coil domains, which starts at roughly 5% macroscopic strain; 2), further transformation of the unraveled coiled-coils into beta-sheet structures, which occurs above roughly 20% macroscopic strain; and 3), spatial expanding of the beta-structured zones from the sample center to its periphery.
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Publication Date: 2004-07-09 PubMed ID: 15240497PubMed Central: PMC1304386DOI: 10.1529/biophysj.103.036749Google Scholar: Lookup
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  • Journal Article

Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

This research paper investigates the transformation of alpha-helices into beta-sheets in hard alpha-keratin fibers, specifically horsehair. The study uses advanced techniques to locate and characterize these structural changes, suggesting it happens in three identifiable stages.

Background of The Research

  • The transformation of alpha-helices into beta-sheets in hard alpha-keratin has been a topic of scientific interest for over half a century.
  • In previous research, the appearance of beta-sheets in stretched keratin fibers was studied. It was noted that the creation of these beta-sheets requires a minimum of 30% relative humidity.
  • This occurrence was observed in the entire tissue, but it was unclear whether the beta-sheets were keratin or matrix proteins and their precise location across the fiber was unidentified.

Methodology

  • In this research, the scientists employed wide-angle x-ray scattering and high spatial resolution infrared microspectroscopy to determine and characterize the structural elements across sections of hair which were stretched in water.
  • This investigative approach assisted in capturing new information about the transformation from alpha-helices to beta-sheets in the keratin fibers.

Key Findings

  • From the results, the scientists established that the process of transformation can be divided into three phases.
  • The first stage involves the unraveling of the alpha-helical coiled-coil domains, a process that initiates at approximately 5% macroscopic strain.
  • This progression leads to the second stage, which is the transformation of the unraveled coiled-coils into beta-sheet structures. This phase occurs once the strain level exceeds around 20%.
  • In the last phase, there is a spatial expansion of the beta-structured zones, moving from the center of the sample to its periphery.

Conclusions and Future Implications

  • This research advances our understanding of the transformation process in hard alpha-keratin fibers, offering more detailed insight into how and when these changes take place.
  • The characterization of each phase of transformation could benefit future studies, potentially opening new fields of investigation for alpha-helix to beta-sheet transitions.

Cite This Article

APA
Kreplak L, Doucet J, Dumas P, Briki F. (2004). New aspects of the alpha-helix to beta-sheet transition in stretched hard alpha-keratin fibers. Biophys J, 87(1), 640-647. https://doi.org/10.1529/biophysj.103.036749

Publication

Biophysical journal
ISSN: 0006-3495
NlmUniqueID: 0370626
Country: United States
Language: English
Volume: 87
Issue: 1
Pages: 640-647

Researcher Affiliations

Kreplak, L
  • Laboratoire pour l'Utilisation du Rayonnement, Centre Universitaire Paris-Sud, 91898, Orsay cedex, France.
Doucet, J
    Dumas, P
      Briki, F

        MeSH Terms

        • Animals
        • Hair / chemistry
        • Horses
        • Keratins / chemistry
        • Protein Conformation
        • Protein Structure, Secondary
        • Spectroscopy, Fourier Transform Infrared / methods
        • X-Rays

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