We studied the adhesive gumfoot silk from the cobweb of western black widow to understand how its composition correlates with adhesion. Solution-State NMR showed the water soluble part of the silk to be composed of majorly hygroscopic organic salts. A previously unknown water insoluble residue was found on the water washed silk threads, characterized using staining and Solid-State NMR studies was identified to consist of glycoprotein. Whole thread adhesion and Solid State NMR results showed the importance of water soluble components in humidity response while optimization of silk adhesion was seen at 30% R.H. Our study highlights the recurring observation of how salts and proteins interact to produce the adhesion of capture silk in different humid environments, a lesson that can provide clues in developing humidity responsive synthetic adhesive systems.
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