Chirality in nature l Natural amino acids are enantiomerically pure These are the building blocks of proteins and enzymes NH> Ho6 alanine phenylalanine histidine Why this enantiomer?Who knows... But why just one enantiomer is more obvious... 胰岛素 Insulin C254H3776507656 Insulin is made of 2 peptide chains-1x30 amino acids 1x21 amino acids Potentially 2.25 x 1015 diastereoisomers A relatively small protein is ribonuclease at 124 amino acids or Potentially 2.13 x 1037 diastereoisomers胰岛素