title: Molecular dynamics of hemoglobin subunits as seen by fluorescence spectroscopy.
abstract: Fluorescent conjugates of beta A subunits and their respective heme-free derivatives have been prepared in which a 1,5-N-iodoacetylaminoethyl-5-naphthylamine-1-sulfonate probe has been specifically placed at the beta-93 or beta-112 cysteine. The fluorescence anisotropy decay and static fluorescence polarization of these conjugates have been examined. Fluorescence measurements have also been made using 1-anilino-8-naphthalenesulfonate complexes, as well as the intrinsic fluorescence of the tryptophan groups. For the cases of the beta-93 and beta-112 conjugates there is substantial evidence for internal rotational freedom of the subunits. The internal mobility of the polypeptide is especially pronounced for the beta-112 conjugate. In contrast, the 1-anilino-8-naphthalenesulfonate probe placed within the heme pocket shows no indication of any rotation, other than that associated with the entire beta-subunit. Tryptophan fluorescence has been measured for the apo-beta subunits and for the peptides beta (1-55) from hemoglobins A and S. Perrin-Weber plots show the presence of multiple rotational modes suggesting mobility of the tryptophan groups.
mesh_terms: D000817:Anilino Naphthalenesulfonates; D005454:Fluorescence Polarization; D005456:Fluorescent Dyes; D006441:Hemoglobin A; D006451:Hemoglobin, Sickle; D006454:Hemoglobins; D006801:Humans; D007460:Iodoacetamide / Q000031:analogs & derivatives; D007700:Kinetics; D046911:Macromolecular Substances; D008433:Mathematics; D008970:Molecular Weight; D009282:Naphthalenesulfonates; D011487:Protein Conformation
chemical_list: D000817:Anilino Naphthalenesulfonates; D005456:Fluorescent Dyes; D006451:Hemoglobin, Sickle; D006454:Hemoglobins; D046911:Macromolecular Substances; D009282:Naphthalenesulfonates; C006421:1,5-I-AEDANS; D006441:Hemoglobin A; D007460:Iodoacetamide