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Development and Synthesis of Optical/MR Contrast Agents for Detection of beta-Galactosidase Activity

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Brud,  A
Former Department MRZ, Max Planck Institute for Biological Cybernetics, Max Planck Society;
Max Planck Institute for Biological Cybernetics, Max Planck Society;

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Engelmann,  J
Former Department MRZ, Max Planck Institute for Biological Cybernetics, Max Planck Society;
Max Planck Institute for Biological Cybernetics, Max Planck Society;

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Pfeuffer,  J
Department Physiology of Cognitive Processes, Max Planck Institute for Biological Cybernetics, Max Planck Society;
Max Planck Institute for Biological Cybernetics, Max Planck Society;

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Citation

Brud, A., Engelmann, J., Pfeuffer, J., Ziegler, T., & Ugurbil, K. (2005). Development and Synthesis of Optical/MR Contrast Agents for Detection of beta-Galactosidase Activity. Poster presented at 4th Annual Meeting of the Society for Molecular Imaging (SMI 2005), Köln, Germany.


Cite as: http://hdl.handle.net/11858/00-001M-0000-0013-D455-8
Abstract
Reporter genes are widely applied to study gene expression and regulation in biological systems. Bacterial LacZ gene, which encodes enzyme beta-galactosidase, represents one of the most commonly used reporter genes, among others such as green fluorescent protein and luciferase. Together with fluorogenic and chromogenic substrates of the enzyme beta-galactosidase, LacZ has been utilized as a standard method of assaying clonal insertion, transcriptional activation, protein expression and protein interaction as well. The use of MR detectable substrates provides a new non-invasive tool for detection of gene expression [1]. beta-Galactosidase catalyzes the hydrolysis of the glycosidic bond between the anomeric carbon at position C1 of the beta-D-galactopyranose and an aglycone part. The replacement of hydroxyl groups at positions C2 - C6 of galactopyranose may induce the loss of enzyme activity. However, it offers a possibility to develop new marker molecules for bi-modal detection by MR/optical imaging. Here we report the syntheses of a series of compounds containing a MR detectable part (Gd(III)-DO3A) attached to beta-galactopyranose moiety by different types of linkers, and a chromophore (p-nitrophenol or 7-hydroxy-9H-(1,3-dichloro-9,9-dimethylacridin-2-one) (DDAO) [2]) at the anomeric carbon for testing enzyme activity. The tests are based on colorimetric detection of released yellow p-nitrophenol or the absorbance/fluorescence shift of released DDAO upon beta-galactosidase hydrolysis. These compounds can prove helpful for the development of new gene expression markers offering the possibility of detection by MR and optical imaging. Coupling to molecules which facilitate internalization into cells can provide a new class of intracellular contrast agents.