Strain-Dependent Structural Changes in Major and Minor Ampullate Spider Silk Revealed by Two-Photon Excitation Polarization

Irina Iachina, Jonathan R. Brewer*

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Resumé

Spider silk's mechanical properties make it an interesting material for many industrial applications. The structure and nanoscopic organization of its proteins are the basis of these qualities. In this study, the emission maxima of the autofluorescence from the protein core of major and minor ampullate silk fibers from the orb-web-weaving spider Nephila madagascariensis are determined and found to be 534 ± 11 and 547 ± 19 nm, respectively. Molecular conformational changes during applied strain are observed in both fiber types using two-photon excitation polarization measurements. Our findings showed that within the fibers the autofluorescent dipoles are separated into two distinct populations, one randomly orientated (amorphous regions) and one with aligned dipoles as found in crystalline structures. The crystalline-amorphous ratio was determined, and it was found that the crystalline dipoles made up around 30 and 20% of the autofluorescent dipoles in major and minor ampullate silk fibers, respectively. Using two-photon polarization measurements, it is possible to directly observe that the major and minor ampullate silk fibers structurally adapt to the applied stress, as well as discern different molecular conformational changes between major and minor ampullates. It was seen that the crystalline-amorphous ratio increased, with up to 9% for major fibers and 6% for minor fibers, as strain was applied, suggesting a conformational adaptation of the fiber, interpreted as noncrystalline 310-helices transforming into crystalline β-sheets.

OriginalsprogEngelsk
TidsskriftBiomacromolecules
Vol/bind20
Udgave nummer6
Sider (fra-til)2384-2391
ISSN1525-7797
DOI
StatusUdgivet - 10. jun. 2019

Fingeraftryk

Silk
Photons
Polarization
Fibers
Crystalline materials
Viral Core Proteins
Proteins
Industrial applications
Mechanical properties

Citer dette

@article{0192e697d58e4d3b8e38234176c3974c,
title = "Strain-Dependent Structural Changes in Major and Minor Ampullate Spider Silk Revealed by Two-Photon Excitation Polarization",
abstract = "Spider silk's mechanical properties make it an interesting material for many industrial applications. The structure and nanoscopic organization of its proteins are the basis of these qualities. In this study, the emission maxima of the autofluorescence from the protein core of major and minor ampullate silk fibers from the orb-web-weaving spider Nephila madagascariensis are determined and found to be 534 ± 11 and 547 ± 19 nm, respectively. Molecular conformational changes during applied strain are observed in both fiber types using two-photon excitation polarization measurements. Our findings showed that within the fibers the autofluorescent dipoles are separated into two distinct populations, one randomly orientated (amorphous regions) and one with aligned dipoles as found in crystalline structures. The crystalline-amorphous ratio was determined, and it was found that the crystalline dipoles made up around 30 and 20{\%} of the autofluorescent dipoles in major and minor ampullate silk fibers, respectively. Using two-photon polarization measurements, it is possible to directly observe that the major and minor ampullate silk fibers structurally adapt to the applied stress, as well as discern different molecular conformational changes between major and minor ampullates. It was seen that the crystalline-amorphous ratio increased, with up to 9{\%} for major fibers and 6{\%} for minor fibers, as strain was applied, suggesting a conformational adaptation of the fiber, interpreted as noncrystalline 310-helices transforming into crystalline β-sheets.",
author = "Irina Iachina and Brewer, {Jonathan R.}",
year = "2019",
month = "6",
day = "10",
doi = "10.1021/acs.biomac.9b00368",
language = "English",
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pages = "2384--2391",
journal = "Biomacromolecules",
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publisher = "American Chemical Society",
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Strain-Dependent Structural Changes in Major and Minor Ampullate Spider Silk Revealed by Two-Photon Excitation Polarization. / Iachina, Irina; Brewer, Jonathan R.

I: Biomacromolecules, Bind 20, Nr. 6, 10.06.2019, s. 2384-2391.

Publikation: Bidrag til tidsskriftTidsskriftartikelForskningpeer review

TY - JOUR

T1 - Strain-Dependent Structural Changes in Major and Minor Ampullate Spider Silk Revealed by Two-Photon Excitation Polarization

AU - Iachina, Irina

AU - Brewer, Jonathan R.

PY - 2019/6/10

Y1 - 2019/6/10

N2 - Spider silk's mechanical properties make it an interesting material for many industrial applications. The structure and nanoscopic organization of its proteins are the basis of these qualities. In this study, the emission maxima of the autofluorescence from the protein core of major and minor ampullate silk fibers from the orb-web-weaving spider Nephila madagascariensis are determined and found to be 534 ± 11 and 547 ± 19 nm, respectively. Molecular conformational changes during applied strain are observed in both fiber types using two-photon excitation polarization measurements. Our findings showed that within the fibers the autofluorescent dipoles are separated into two distinct populations, one randomly orientated (amorphous regions) and one with aligned dipoles as found in crystalline structures. The crystalline-amorphous ratio was determined, and it was found that the crystalline dipoles made up around 30 and 20% of the autofluorescent dipoles in major and minor ampullate silk fibers, respectively. Using two-photon polarization measurements, it is possible to directly observe that the major and minor ampullate silk fibers structurally adapt to the applied stress, as well as discern different molecular conformational changes between major and minor ampullates. It was seen that the crystalline-amorphous ratio increased, with up to 9% for major fibers and 6% for minor fibers, as strain was applied, suggesting a conformational adaptation of the fiber, interpreted as noncrystalline 310-helices transforming into crystalline β-sheets.

AB - Spider silk's mechanical properties make it an interesting material for many industrial applications. The structure and nanoscopic organization of its proteins are the basis of these qualities. In this study, the emission maxima of the autofluorescence from the protein core of major and minor ampullate silk fibers from the orb-web-weaving spider Nephila madagascariensis are determined and found to be 534 ± 11 and 547 ± 19 nm, respectively. Molecular conformational changes during applied strain are observed in both fiber types using two-photon excitation polarization measurements. Our findings showed that within the fibers the autofluorescent dipoles are separated into two distinct populations, one randomly orientated (amorphous regions) and one with aligned dipoles as found in crystalline structures. The crystalline-amorphous ratio was determined, and it was found that the crystalline dipoles made up around 30 and 20% of the autofluorescent dipoles in major and minor ampullate silk fibers, respectively. Using two-photon polarization measurements, it is possible to directly observe that the major and minor ampullate silk fibers structurally adapt to the applied stress, as well as discern different molecular conformational changes between major and minor ampullates. It was seen that the crystalline-amorphous ratio increased, with up to 9% for major fibers and 6% for minor fibers, as strain was applied, suggesting a conformational adaptation of the fiber, interpreted as noncrystalline 310-helices transforming into crystalline β-sheets.

U2 - 10.1021/acs.biomac.9b00368

DO - 10.1021/acs.biomac.9b00368

M3 - Journal article

VL - 20

SP - 2384

EP - 2391

JO - Biomacromolecules

JF - Biomacromolecules

SN - 1525-7797

IS - 6

ER -