Adhesive Spider Silks for Naval Applications
Abstract
All spiders produce silks and most spiders have multiple silk glands, which secrete different silk materials that are optimized for different biological functions. There are seven different spider silk glands that each produces a distinct silk for a specific function: 1) Aciniform gland: Used to wrap and secure freshly captured prey; used in the male sperm webs; used in stabilimenta. 2) Cylindriform/Tubuliform gland: egg cocoon silk – used for protective egg sacs. 3) Ampullate glands (major): dragline silk – used for the web’s outer rim and spokes and the lifeline. 4) Ampullate glands (minor): used for temporary scaffolding during web construction. 5) Pyriform gland: attaching threads – attachment discs are made which anchor a thread to a surface or another thread; used to form bonds between separate threads for attachment points. 6) Flagelliform gland: Capture-spiral silk – used for the capturing lines of the web. 7) Aggregate gland: outer part of sticky silk – droplets of an adhesive substance are deposited along the threads; a silk glue of sticky globules. A male spider has at least three silk glands (dragline, attachment and swathing silk) and a female has at least four silk glands (dragline, attachment, swathing silk, and egg sac silk). Silks have evolved with mechanical and chemical (amino acid composition) properties suitable for the different uses and they include both fibers and glues (e.g. aggregate silk and piriform silk). Piriform silk comes out in dozens of small fibers (nm diameter) that become entangled on any rough surface and adhere strongly upon contact. It is unknown if the fibers adhere wet or dry. This material is an adhesive and behaves like a single sided Velcro sticking to a wide variety of surfaces including skin, metal, plastic, vertical glass plates, and wet areas (for spiders anchoring webs in an aqueous environment). However, nothing is known about the mechanical or adhesive properties of piriform fibers since they are too small in length to allow testing. The Principal Investigator has cloned the piriform gene encoding the fibrous protein adhesive from Nephial clavipes (a species of golden-orb weaver) and established that its protein sequence is different from any other silk protein from orb-weaving spiders as well as the sequence of cob-weaving spider piriform silk protein. There was no evidence for the cob-weaving protein sequence in the orb-weaving spiders and no evidence of orb-weaver sequence in the cob-weaving spiders. This suggests that there was a large divergence in this protein unlike that observed for the other silk proteins between the two groups that are highly similar in protein sequence. The orb-weaver piriform protein is composed of repeats of two new amino acid sequences (QQSSVAQC and RPLPVPQP, where Q = glutamine, S = serine, V = valine, A = alanine, C = cysteine, R = arginine, P = proline, and L = leucine) linked to each other in a highly conserved amino acid sequence. Due to the high conservation of all three segments of the overall repeat in three diverse spider species, the Principal Investigator has hypothesized that each segment contributes different features to the protein and its adhesive properties. This project will assess whether piriform silk can serve as a novel solid adhesive with properties applicable to Navy applications. Three new recombinant proteins that are based on the piriform amino acid sequences will be expressed from constructed piriform-like genes in E. coli bacteria to produce enough material to enable adhesive testing. Two of the recombinant proteins mimic each of the new repeat sequence regions and the third mimics the full-length repeat of all three regions. Bacterial expression will be used for these studies since there is no evidence for glycosylation of these proteins.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Aug 12, 2016
- Source ID
- N000141512501
Entities
People
- Randolph V Lewis
Organizations
- Office of Naval Research
- United States Navy
- Utah State University