title: A re-examination of the circular dichroism of the calicheamicin enediyne/dienone chromophoric interaction.
abstract: A series of calicheamicin derivatives have been made in an effort to delineate the origin of the strong circular dichroism (CD) of calicheamicin reported previously. The CD spectrum of calicheamicin (I) was compared with that of fragments II and III, which contain either the enediyne/dienone or a thiobenzoate chromophore alone. NaBH(4) reduction of calicheamicin produced two analogues (IV and V) that have no dienone. This allowed the assessment of possible exciton coupling between the enediyne on the warhead and the thiobenzoate on the tail. It was found that the strong negative 312/272 nm exciton split in the CD of calicheamicin is due largely to the enediyne/dienone interaction. Contributions from the thiobenzoate or its interaction with the enediyne have been ruled out. [structure: see text]
authors.affiliation: Biophysics/Enzymology, Chemical and Screening Sciences, Wyeth Research, Pearl River, NY 10965, USA. dingw@wyeth.com
authors.forename: Weidong
authors.initials: W
authors.lastname: Ding
authors.forename: Keith
authors.initials: K
authors.lastname: Pitts
authors.forename: George A
authors.initials: GA
authors.lastname: Ellestad
authors.forename: Girija
authors.initials: G
authors.lastname: Krishnamurthy
mesh_terms: D000617:Aminoglycosides / Q000737:chemistry*; D000970:Antineoplastic Agents / Q000737:chemistry; D001565:Benzoates / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid; D002942:Circular Dichroism; D053281:Enediynes; D015394:Molecular Structure; D011092:Polyethylene Glycols / Q000737:chemistry*; D013053:Spectrophotometry
chemical_list: D000617:Aminoglycosides; D000970:Antineoplastic Agents; D001565:Benzoates; D053281:Enediynes; C489065:calicheamicin dienone; C489066:calicheamicin enediyne; C489064:thiobenzoate chromophore; D011092:Polyethylene Glycols