1. Tennis Racquet Strings (Natural Gut)

2. How It Is Made Natural gut’s main source is a cow intestine called serosa. It is long and has great tensile strength. The collagen found in serosa has a molecular make up that is designed to withstand the stretching and contraction of the intestine. It takes three cows to produce one set of tennis string. To produce this string is a very long, involved process. Once the serosa is removed from the cow, it is cut into long ribbons, which go through a long cleaning process afterward. Although it varies depending on the manufacturer, the ribbons are most of the time put into a variety of baths. The purpose of this is to remove impurities without harming anything. Sometimes, the string is bleached to remove the orange color of the ribbons. http://www.tennis-warehouse.com/lc/Naturalgut.html

3. How It Is Made Once the ribbons have been washed, they are subjected to more quality control. The manufacturer may add some color to the string. The ribbons are then bound together on tension racks and the drying process begins. This process is carefully controlled down to the climate. It might even take several days. Once bound together they will finally start to look like string. It needs to be polished for smoothness and checked to make sure it meets the correct gauge specifications. At this point, most manufacturers will coat the string with a special polyurethane coating to improve abrasion and water resistance. The string is finally prepared for packaging. http://www.tennis- warehouse.com/lc/Naturalgut.html

4. Composition Collagen has a triple helix molecular structure. It is made of three polypeptide strands stabilized by numerous hydrogen bonds. It is the single most abundant protein in the animal kingdom. Collagen’s structural unit is 300-nm long and 1.5-nm in diameter. It consists of three coiled subunits: two α1(I) chains and one α2(I). * Each chain contains 1050 amino acids. * The triple-helical structure arises from an abundance of three amino acids, which include glycine, proline, and hydroxyproline. Hydrogen bonds linking the peptide bond NH of a glycine residue with a peptide carbonyl (C ═ O) group in an adjacent polypeptide help hold the three chains together. The fixed angle of the C – N peptidyl-proline or peptidyl-hydroxyproline bond enables each polypeptide chain to fold into a helix http://www.ncbi.nlm.nih.gov/books/NBK21582/

5. http://liamscheff.com/wp-content/uploads/2010/02/collagen- molecule-fibril.jpg http://web.mit.edu/course/3/3.082/www/team1_f02/pictures/collag enstructure.jpg

6. LEWIS DOT STRUCTURE http://ars.els-cdn.com/content/image/1-s2.0-S8756328202008505- gr1.gif