Characterization of a Protein-based Adhesive Elastomer Secreted by the Australian Frog Notaden bennetti

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• 作者：Lloyd D. Graham ; Veronica Glattauer ; Mickey G. Huson ; Jane M. Maxwell ; Robert B. Knott ; John W. White ; Paul R. Vaughan ; Yong Peng ; Michael J. Tyler ; Jerome A. Werkmeister ; and John A. Ramshaw
• 刊名：Biomacromolecules
• 出版年：2005
• 出版时间：November 2005
• 年：2005
• 卷：6
• 期：6
• 页码：3300 - 3312
• 全文大小：774K
• 年卷期：v.6,no.6(November 2005)
• ISSN：1526-4602

文摘

When provoked, Notaden bennetti frogs secrete an exudate which rapidly forms a tacky elastic solid ("frogglue"). This protein-based material acts as a promiscuous pressure-sensitive adhesive that functions even inwet conditions. We conducted macroscopic tests in air to assess the tensile strength of moist glue (up to 78± 8 kPa) and the shear strength of dry glue (1.7 ± 0.3 MPa). We also performed nanomechanicalmeasurements in water to determine the adhesion (1.9-7.2 nN or greater), resilience (43-56%), and elasticmodulus (170-1035 kPa) of solid glue collected in different ways. Dry glue contains little carbohydrateand consists mainly of protein. The protein complement is rich in Gly (15.8 mol %), Pro (8.8 mol %), andGlu/Gln (14.1 mol %); it also contains some 4-hydroxyproline (4.6 mol %) but no 5-hydroxylysine or 3,4-dihydroxyphenylalanine (L-Dopa). Denaturing gel electrophoresis of the glue reveals a characteristic patternof proteins spanning 13-400 kDa. The largest protein (Nb-1R, apparent molecular mass 350-500 kDa) isalso the most abundant, and this protein appears to be the key structural component. The solid glue can bedissolved in dilute acids; raising the ionic strength causes the glue components to self-assemble spontaneouslyinto a solid which resembles the starting material. We describe scattering studies on dissolved and solidglue and provide microscopy images of glue surfaces and sections, revealing a porous interior that is consistentwith the high water content (85-90 wt %) of moist glue. In addition to compositional similarities withother biological adhesives and well-known elastomeric proteins, the circular dichroism spectrum of dissolvedglue is almost identical to that for soluble elastin and electron and scanning probe microscopy images invitecomparison with silk fibroins. Covalent cross-linking does not seem to be necessary for the glue to set.