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Abstract #0159

Bioengineering a Reporter System That Combines a Highly Sensitive CEST and Fluorescence Imaging Probe

Amnon Bar-Shir1, 2, Yoshinori Kato1, Arvind P. Pathak1, Jeff W.M. Bulte1, 2, Assaf A. Gilad1, 2

1Department of Radiology, Johns Hopkins University, Baltimore, MD, United States; 2Institute for Cell Engineering, Johns Hopkins University, Baltimore, MD, United States

The Drosophila melanogaster 2-deoxynucleoside kinase (Dm-dNK) enzyme phosphorylates a wide range of nucleoside analogs, including the fluorescent nucleoside pyrrolo-2-deoxycytidine (pyrrolo-dC). We show here that the NH proton of the pyrrolo-dC generates high CEST contrast when a saturation pulse is applied at 5.8ppm from the water protons. The formation of the pyrrolo-dC monophosphate by recombinant Dm-dNK resulted in accumulation of the probe selectively in the cytoplasm of Dm-dNK-expressing cells since its negative charge prevents cellular export. Hence, pyrrolo-dC can be used for monitoring the reporter gene Dm-dNK expression with CEST MRI.