... acids, the last three being an L-lysine and two D-alanines An enzyme called transpeptidase then hooks these peptide chains together, removing the final D-alanine and attaching the penul- timate D-alanine ... living for.” www.sciam.com SCIENTIFIC AMERICAN Copyright 2001 Scientific American, Inc 33 Copyright 2001 Scientific American, Inc THE SE M A N T I C WEB A new form of Web content that is meaningful ... age of the universe, leaving astronomers to wonder whether cosmological theories had some fatal flaw 44 SCIENTIFIC AMERICAN Copyright 2001 Scientific American, Inc Copyright 2001 Scientific American, ...