Chirality in nature I Natural amino acids are enantiomerically pure These are the building blocks of proteins and enzymes HO2C Me 入K7 H02C、 NH, NH2 alanine phenylalanine histidine Why this enantiomer?Who knows.. But why just one enantiomer is more obvious... 胰岛素 1ns如m C254H377M6507656 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