BIOMIMETIC MANUFACTURING OF FIBERS

INTRODUCTION

Biotechnology provides the tools to clone and express designed synthetic protein fibers in simple organisms. Spider dragline silk is a natural protein polymer with many desirable properties, which we, and others, have used as a model. Two partial cDNA sequences corresponding to the genes encoding for the ß-sheet proteins (spidroin 1 and spidroin 2) of the dragline silk of the golden orb weaver spider (Nephila clavipes) have been isolated and published by other workers 1,2. Synthetic genes corresponding to these natural genes were cloned, then expressed in E. coli 3,4, and in yeast 5,6. A partial cDNA clone corresponding to the 3' end of the dragline silk gene has also been isolated, cloned and expressed in E. coli 7. Our goal is to produce silk-like material from spidroin 1 or spidroin 2 homopolymers, and from spidroin 1/spidroin 2 or collagen/spidroin heteropolymers by genetic engineering in yeast (Pichia pastoris) and other plants (in particular, seed storage protein-producing plants where it may be possible to produce significant quantities of these proteins). We are using parts of the omega-helical collagen protein (mi-col-2 gene) in the root-knot nematode Meloidogyne incognita cuticle8. For production in plants, we are exploring the use of natural high level seed specific promoters such as the omega-9 desaturase gene. The omega-9 desaturase transcript has been shown to accumulate to very high concentrations in peanut9 and sunflower10 developing seeds. We are now characterizing genomic clones of this gene in peanut to obtain its promoter. A study of the structural and functional biology of the spinning apparatus of N. clavipes has been undertaken. While much of the study has been a compilation of extant literature, we have conducted some studies in our laboratory. The results of this study have been critical to the design of our biomimetic spinning system. In addition, live spiders are maintained in a walk-in enclosure and are “milked” for their dragline silk. The current objective for study of the silk samples is to determine the piezoelectric properties of the silk. We are also conducting Raman spectroscopy and X-Ray Diffraction studies on the samples. The results of this aspect of our program will support our goal to improve understanding of the process/structure/property relations in natural spider silk, and (eventually) in Biomimetic materials