Heme proteins are underutilized scaffolds for biological sensing and imaging. Traditional methods for the incorporation of unnatural metalloporphyrins into heme proteins involve harsh conditions that have limited the number of viable heme protein constructs. To generate contrast agents for magnetic resonance imaging (MRI), an expression-based methodology is used to incorporate Mn- and Gd-containing porphyrins into the Heme Nitric oxide/OXygen binding (H-NOX) domain from Thermoanaerobacter tengcongensis (Tt H-NOX). Purified Tt H-NOX was found to provide a highly stable coordination environment for the unnatural porphyrins under biological conditions (>24 h at 37 �C in plasma). T1 and T2 relaxivities measured for Tt H-NOX bound to its native ferric heme and the unnatural [Mn(III), Mn(II), and Gd(III)] porphyrins were higher than commercial small molecule MRI contrast agents. H-NOX�based contrast agents are highly tunable frameworks that having promising coordination and imaging properties for future biological use.

High-relaxivity and high-stability porphyrin-substituted H-NOX proteins for magnetic resonance imaging technology

243rd National Meeting (2012)

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