Composition
The type and percentage of amino acids in the A. at- las fibers was determined using a Hitachi L-8800A amino acid analyzer. Norleucine was used as the inter- nal standard for both the samples and the control for amino acid analysis. Samples were first evaporated to dryness in a speedvac and later hydrolyzed in liquid
6 N HCl under argon atmosphere. After 20 h of hydro- lysis at 110° C, the samples were evaporated to dry- ness, then redissolved in 200 μL of 0.02 N HCl. Fifty microliters was injected automatically onto the Hit- achi Amino Acid Analyzer to determine the amino acid type and content. In data analysis, correction was made to the amount of the internal standard, to mini- mize dilutional errors.