Direct Solvation of Glycoproteins by Salts in Spider Silk Glues Enhances Adhesion and Helps To Explain the Evolution of Modern Spider Orb Webs

The evolutionary origin of modern viscid silk orb webs from ancient cribellate silk ancestors is associated with a 95% increase in diversity of orb-weaving spiders, and their dominance as predators of flying insects, yet the transition’s mechanistic basis is an evolutionary puzzle. Ancient cribellat...

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Bibliographic Details
Published in:Biomacromolecules 2014-04, Vol.15 (4), p.1225-1232
Main Authors: Sahni, Vasav, Miyoshi, Toshikazu, Chen, Kelley, Jain, Dharamdeep, Blamires, Sean J, Blackledge, Todd A, Dhinojwala, Ali
Format: Article
Language:English
Subjects:
Adhesiveness
Animals
Applied sciences
Arachnida
Araneae
Biochemistry. Physiology. Immunology
Biological and medical sciences
Biological Evolution
Exact sciences and technology
Fibers and threads
Forms of application and semi-finished materials
Fundamental and applied biological sciences. Psychology
Glycoproteins - chemistry
Invertebrates
Magnetic Resonance Spectroscopy
Models, Theoretical
Physiology. Development
Polymer industry, paints, wood
Salts - chemistry
Silk - chemistry
Spiders
Technology of polymers
Water - chemistry
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Summary:The evolutionary origin of modern viscid silk orb webs from ancient cribellate silk ancestors is associated with a 95% increase in diversity of orb-weaving spiders, and their dominance as predators of flying insects, yet the transition’s mechanistic basis is an evolutionary puzzle. Ancient cribellate silk is a dry adhesive that functions through van der Waals interactions. Viscid threads adhere more effectively than cribellate threads because of the high extensibility of their axial silk fibers, recruitment of multiple glue droplets, and firm adhesion of the viscid glue droplets. Viscid silk’s extensibility is permitted by the glue’s high water content, so that organic and inorganic salts present in viscid glue droplets play an essential role in contributing to adhesion by sequestering the atmospheric water that plasticizes the axial silk fibers. Here, we provide direct molecular and macro-scale evidence to show that salts also cause adhesion by directly solvating the glycoproteins, regardless of water content, thus imparting viscoelasticity and allowing the glue droplets to establish good contact. This “dual role” of salts, plasticizing the axial silk indirectly through water sequestration and directly solvating the glycoproteins, provides a crucial link to the evolutionary transition from cribellate silk to viscid silk. In addition, salts also provide a simple mechanism for adhering even at the extremes of relative humidity, a feat eluding most synthetic adhesives.
ISSN:1525-7797
1526-4602
DOI:10.1021/bm401800y