title: Fab MOR03268 triggers absorption shift of a diagnostic dye via packaging in a solvent-shielded Fab dimer interface.
abstract: Molecular interactions between near-IR fluorescent probes and specific antibodies may be exploited to generate novel smart probes for diagnostic imaging. Using a new phage display technology, we developed such antibody Fab fragments with subnanomolar binding affinity for tetrasulfocyanine, a near-IR in vivo imaging agent. Unexpectedly, some Fabs induced redshifts of the dye absorption peak of up to 44 nm. This is the largest shift reported for a biological system so far. Crystal structure determination and absorption spectroscopy in the crystal in combination with microcalorimetry and small-angle X-ray scattering in solution revealed that the redshift is triggered by formation of a Fab dimer, with tetrasulfocyanine being buried in a fully closed protein cavity within the dimer interface. The derived principle of shifting the absorption peak of a symmetric dye via packaging within a Fab dimer interface may be transferred to other diagnostic fluorophores, opening the way towards smart imaging probes that change their wavelength upon interaction with an antibody.
authors.affiliation: Bayer Schering Pharma AG, Global Drug Discovery, 13342 Berlin, Germany. roman.hillig@bayerhealthcare.com
authors.forename: Roman C
authors.initials: RC
authors.lastname: Hillig
authors.forename: Stefanie
authors.initials: S
authors.lastname: Urlinger
authors.forename: Jörg
authors.initials: J
authors.lastname: Fanghänel
authors.forename: Bodo
authors.initials: B
authors.lastname: Brocks
authors.forename: Cornelia
authors.initials: C
authors.lastname: Haenel
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Stark
authors.forename: Detlev
authors.initials: D
authors.lastname: Sülzle
authors.forename: Dmitri I
authors.initials: DI
authors.lastname: Svergun
authors.forename: Siegfried
authors.initials: S
authors.lastname: Baesler
authors.forename: Guido
authors.initials: G
authors.lastname: Malawski
authors.forename: Dieter
authors.initials: D
authors.lastname: Moosmayer
authors.forename: Andreas
authors.initials: A
authors.lastname: Menrad
authors.forename: Michael
authors.initials: M
authors.lastname: Schirner
authors.forename: Kai
authors.initials: K
authors.lastname: Licha
mesh_terms: D000042:Absorption; D000595:Amino Acid Sequence; D000911:Antibodies, Monoclonal / Q000737:chemistry / Q000276:immunology*; D000915:Antibody Affinity; D002151:Calorimetry; D002850:Chromatography, Gel; D004396:Coloring Agents / Q000737:chemistry*; D022801:Complementarity Determining Regions / Q000737:chemistry; D018360:Crystallography, X-Ray; D019281:Dimerization; D005453:Fluorescence; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000737:chemistry* / Q000276:immunology*; D007211:Indoles / Q000737:chemistry* / Q000276:immunology*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019151:Peptide Library; D053838:Scattering, Small Angle; D012997:Solvents / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet
chemical_list: D000911:Antibodies, Monoclonal; D004396:Coloring Agents; D022801:Complementarity Determining Regions; C527478:Fab MOR03268; D007140:Immunoglobulin Fab Fragments; D007211:Indoles; D019151:Peptide Library; D012997:Solvents