Structure–Property and Structure–Function Relations of Leafhopper (Kahaono montana) Silk

Jung C. Chang; Geoff M. Gurr; Murray J. Fletcher; Robert G. Gilbert

doi:10.1071/CH06179

RESEARCH ARTICLE

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Structure–Property and Structure–Function Relations of Leafhopper (Kahaono montana) Silk

Jung C. Chang ^A , Geoff M. Gurr ^B , Murray J. Fletcher ^C and Robert G. Gilbert ^A ^D

+ Author Affiliations

- Author Affiliations

^A Key Centre for Polymer Colloids, School of Chemistry, University of Sydney, Sydney NSW 2006, Australia.

^B Pest Biology and Management Group, Charles Sturt University, Orange NSW 2800, Australia.

^C New South Wales Department of Primary Industry, Orange Agricultural Institute, Orange NSW 2800, Australia.

^D Corresponding author. Email: gilbert@chem.usyd.edu.au

Australian Journal of Chemistry 59(8) 579-585 https://doi.org/10.1071/CH06179
Submitted: 29 May 2006 Accepted: 4 August 2006 Published: 8 September 2006

Abstract

Kahaono montana Evans (Insecta: Hemiptera: Cicadellidae), an endemic Australian leafhopper, is unique among the insect order Hemiptera in producing a silk. In this study, the secondary structure of the protein comprising leafhopper silk, and the surface stretching mechanical properties of this biopolymer, were investigated using Fourier-transform infrared microscopy and atomic force microscopy, respectively. The curve-fitted amide I and amide III bands revealed a composition of 13.1% α-helix, 23.8% β-sheet, 25.5% random coil, and 37.6% aggregated side chains. The molecular stretching behaviour of raw and cleaned silk fibres differed markedly. Analysis of the AFM force curves showed an adhesive property of the raw silk, while the pure fibre showed only the presence of protein. These findings suggest that the silk fibres act as a structural support for other leafhopper secretions and together form a hydrophobic barrier that may protect the insects from rain and natural enemies. This is the first time such a use of silk has been found in a biological system.

Acknowledgements

The authors acknowledge the facility and technical assistance from Drs Elisabeth Carter, Annabelle Bloom, and Pall Thordarson in the School of Chemistry, University of Sydney, as is collaboration with the University of Sydney Electron Microscope Unit. The authors also acknowledge the Rural Management Research Institute, University of Sydney. The support of a LIEF grant from the Australian Research Council is gratefully acknowledged. The Key Centre for Polymer Colloids was established and supported by the ARC’s Research Centres program.

References

Structure–Property and Structure–Function Relations of Leafhopper (Kahaono montana) Silk

Abstract

Acknowledgements

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