Key componentsare of health are L-cysteine or its disulfide, L-cystine. Cysteamine, and its disulfide, cystamine, uncouple reactions producing thyroid hormones at concentrations approaching millimolar. Homocysteine is just toxic. Pencillamine, promoted as a chelator for toxic metals, is fairly toxic, itself.. Recently, N-acetylcysteine (NAC) was shown to cause autoimmune reactions, NAC being a “NACty” analogue of L-cysteine and vitalethine. Remember the old “It's not nice to fool with Mother Nature” commercials? Were old margarine commercials just legal disclaimers for fats made trans, toxic, and carcinogenic by hydrogenation with nickel? “Close” only counts with horseshoes, hand grenades, and nuclear warheads, NOT with Mother Nature!