Fab MOR03268 triggers absorption shift of a diagnostic dye via packaging in a solvent-shielded Fab dimer interface |
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Authors: | Hillig Roman C Urlinger Stefanie Fanghänel Jörg Brocks Bodo Haenel Cornelia Stark Yvonne Sülzle Detlev Svergun Dmitri I Baesler Siegfried Malawski Guido Moosmayer Dieter Menrad Andreas Schirner Michael Licha Kai |
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Institution: | 1 Bayer Schering Pharma AG, Global Drug Discovery, 13342 Berlin, Germany 2 Morphosys AG, Lena-Christ-Strasse 48, 82152 Martinsried, Germany 3 European Molecular Biology Laboratory, Hamburg Outstation, Notkestrasse 85, 22603 Hamburg, Germany 4 Institute of Crystallography, Russian Academy of Sciences, Leninsky pr. 59, 117333 Moscow, Russia |
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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. |
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Keywords: | TSC tetrasulfocyanine SAXS small-angle X-ray scattering ITC isothermal titration calorimetry MM molecular mass MO molecular orbital BSA bovine serum albumin |
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