5. Amino acids. The side chains of amino acids have a wide spectrum of chemical and physical properties. In each space provided below, write the single-letter abbreviations of all amino acids that match the description. positively charged side chains at pH7.4 negatively charged side chains at pH7.4 negatively charged side chains at pH12 achiral contains two chiral carbons side chain restricts the rotation of main chain contains carboxamide side chains often found in the active site of enzymes, where it can serve as either acid or base catalyst least soluble in water [Hint: see Table 12.2 in textbook.] most soluble in water contains hydroxyl groups N-terminal amino acid residue of proteins often found in -turns, rarely found in -helices can form disulfide crosslinks under oxidizing conditions, especially in extracellular proteins attachment sites of sugars in glycoproteins [Hint: see Chapter 11 in textbook.]