Analyzing the clustering effects of major ampullate silk mechanical properties - biomed 2009

Although spider silk displays an amazing combination of strength and extensibility unrivalled by most synthetic biomaterials, its molecular architecture is relatively simplistic. Four primary amino acid block motifs (An, (GA)n, GPGXX, GGX) have been correlated with mechanical functions. Recent genetic engineering to control the mechanical behavior of synthetic silk fibers has verified much of the proposed structure/function relationship; however, the genetically defined exchange between strength and elasticity has proven not to be a direct relationship. Thus, complete control over the mechanical properties of a synthetic spider silk based fiber continues to elude scientists. The yet undefined factor(s) may be an element of the fabrication process. Natural silk production results from a combination of dehydration and protein alignment that occurs during concurrent spin and draw processes. While synthetic fiber production attempts to mimic 1) dehydration with a series of coagulating solvents and 2) protein alignment through the controlled extrusion of a concentration dependent spinning solution, the spinning and drawing processes are separated and occur sequentially. Many studies have been conducted which have examined multiple parameters; however, the spinning conditions which produce consistent mechanical properties, necessary for the progression toward any medical, commercial or military application, have not been identified. Here, we report on mathematical methods based on data from a variety of spinning conditions to characterize different impacting properties as either primary (i.e. a condition which directs or dictates mechanical properties of an individual fiber) or ptimizing (i.e. a condition which increases the engineered properties of the silk).