title: (Strept)avidin as host for biotinylated coordination complexes: stability, chiral discrimination, and cooperativity.
abstract: Incorporation of a biotinylated ruthenium tris(bipyridine) [Ru(bpy)(2)(Biot-bpy)](2+) (1) in either avidin or streptavidin-(strept)avidin-can be conveniently followed by circular dichroism spectroscopy. To determine the stepwise association constants, cooperativity, and chiral discrimination properties, diastereopure (Lambda and Delta)-1 species were synthesized and incorporated in tetrameric (strept)avidin to afford (Delta-[Ru(bpy)(2)(Biot-bpy)](2+))(x)() subsetavidin, (Lambda-[Ru(bpy)(2)(Biot-bpy)](2+))(x)() subsetavidin, (Delta-[Ru(bpy)(2)(Biot-bpy)](2+))(x)() subsetstreptavidin, and (Lambda-[Ru(bpy)(2)(Biot-bpy)](2+))(x)() subsetstreptavidin (x = 1-4) For these four systems, the overall stability constants are log beta(4) = 28.6, 30.3, 36.2, and 36.4, respectively. Critical analysis of the CD titrations data suggests a strong cooperativity between the first and the second binding event (x = 1, 2) and a pronounced difference in affinity between avidin and streptavidin for the dicationic guest 1 as well as modest enantiodiscrimination properties with avidin as host.
authors.affiliation: Institute of Chemistry, University of Neuchâtel, Av. Bellevaux 51, CP 2, CH-2007 Neuchâtel, Switzerland.
authors.forename: Andreas
authors.initials: A
authors.lastname: Loosli
authors.forename: Untung Edy
authors.initials: UE
authors.lastname: Rusbandi
authors.forename: Julieta
authors.initials: J
authors.lastname: Gradinaru
authors.forename: Klaus
authors.initials: K
authors.lastname: Bernauer
authors.forename: Carl Wilhelm
authors.initials: CW
authors.lastname: Schlaepfer
authors.forename: Michel
authors.initials: M
authors.lastname: Meyer
authors.forename: Sylwester
authors.initials: S
authors.lastname: Mazurek
authors.forename: Marjana
authors.initials: M
authors.lastname: Novic
authors.forename: Thomas R
authors.initials: TR
authors.lastname: Ward
mesh_terms: D015082:2,2'-Dipyridyl / Q000031:analogs & derivatives* / Q000737:chemistry; D001360:Avidin / Q000737:chemistry; D001426:Bacterial Proteins / Q000138:chemical synthesis / Q000737:chemistry*; D001710:Biotin / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry; D019921:Biotinylation; D056831:Coordination Complexes; D015394:Molecular Structure; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D019809:Streptavidin / Q000737:chemistry*; D013329:Structure-Activity Relationship; D017975:Ruthenium Compounds
chemical_list: D015082:2,2'-Dipyridyl; D001360:Avidin; D001426:Bacterial Proteins; D001710:Biotin; D056831:Coordination Complexes; D019809:Streptavidin; C066114:biotin-streptavidin complex; C547232:tris(2,2-bipyridine)-ruthenium(II); D017975:Ruthenium Compounds