A is for ALANINE, three carbons long; C is for CYSTEINE, with a sulfhydryl prong. D is ASPARTATE, a good proton source, And E, GLUTAMATE, is one also, of course. F, PHENYLALANINE, has benzene on board; GLYCINE, or G, wins the small-size award. H is for HISTIDINE. What a great buffer! And water prompts I, ISOLEUCINE, to suffer. K: LYSINE's high on the pKa scale; L is for LEUCINE, with its long Y-shaped tail. M is METHIONINE, that sulfury lout, And N is ASPARAGINE, an amide, no doubt. P: PROLINE flaunts its odd ring like a bride; Q, GLUTAMINE, is another amide. R, ARGININE, has four nitrogens in all. And S is for SERINE, a petite alcohol. T is for THREONINE, similar to S; V is for VALINE. Aliphatic? Why, yes! W -- that's TRYPTOPHAN -- has rings at the end, And Y, TYROSINE, is the kinases' friend.