Due to their great photophysical and luminescent properties, d6 metal complexes have been of interest in labeling various macromolecules. Octahedral d6metal (Re(I), Ru(II), Os(II), Ir(III)) complexes containing bipyridine or phenanthroline ligands show intense and long-lived luminescence emission amenable for fluorescence detection and electron transfer. To date, the covalent attachment of these complexes to proteins has taken advantage of the specific reactivity of amino acids, especially histidine, lysine and cysteine residues. Engineering of reactive moieties on the metal complexes has resulted in various successful approaches including maleimide, succinimide, bromoalkyl and iodoacetamide derivatives. The low natural abundance and nucleophilicity of cysteine residues has been of particular interest in displacing bromoalkyl and iodoacetamide groups. However, the introduction of such functionality onto bipyridine or phenanthroline ligands requires several synthetic steps.Herein, we report an alternative methodology to label macromolecules. We demonstrated the facile synthesis of the d6 metal complexes mentioned above and illustrated their use in labeling non-native single cysteine residues of P450 BM3 mutants. The metal complexes have been characterized by 1H NMR, mass spectrometry, absorption and luminescence spectroscopies, and cyclic voltammetry. We will also present insights into the labeling mechanism and the identification of intermediates.

Facile and versatile methodology for labeling cysteine residues with fluorescent d<sup>6</sup> metal complexes

246th National Meeting (2013)

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Facile and versatile methodology for labeling cysteine residues with fluorescent d6 metal complexes

Facile and versatile methodology for labeling cysteine residues with fluorescent d⁶ metal complexes