This property is maintained at a wide range of frequencies in an insect protein containing many dityrosine and trityrosine crosslinks. Both a “series” and a “parallel” component with this property are described in Hill’s three element model. Worm-like chains such as DNA inherently have an entropic (-5[1])form of this property, while electrostatic interactions within PEVK regions cause a common example of this property's enthalpic form. This property is conferred (-5[1])by the I-band of the giant protein (*) titin (10[1]-5[1])(“TAI-tin”). Deficiencies (-5[1])in alpha-1 antitrypsin lead to breakdown of tissue (10[2])with this property (10[1])in the lungs, (10[1]-5[1])which may cause COPD. (10[1])Fibrils (10[1])of collagen, (10[3])fibronectin (10[1])and a protein named for this property (10[1])are a primary (10[1])component of the extracellular (10[1])matrix. For 10 points, name this property (10[1])of proteins that return to their original length after being (10[2])stretched. (10[2]) (10[6]0[1])■END■