Synthesis, Characterization and Luminescence Properties of Dipyridin‐2‐ylamine Ligands and Their Bis(2,2′‐bipyridyl)ruthenium(II) Complexes and Labelling Studies of Papain from Carica papaya

Abstract

Two luminescent polypyridyl Ru II complexes including dipyridin-2-ylamine (dpa) ligands functionalized by a maleimide group, namely [Ru(bpy) 2 (1a-b)](PF 6 ) 2 (bpy = 2,2Ј-bipyridyl;, were synthesized, and the X-ray structure of [Ru(bpy) 2 -(1b)](PF 6 ) 2 was solved. The photophysical properties of these complexes and the starting dipyridin-2-ylamine ligands were studied. Upon excitation at their maximum of absorption, the dpa ligands exhibited weak luminescence because of quenching by the maleimide group. Conversely, the complexes displayed noticeable luminescence, with an emission

Examination of abiotic cofactor assembly in photosynthetic biomimetics: site-specific stereoselectivity in the conjugation of a ruthenium(II) tris(bipyridine) photosensitizer to a multi-heme protein

“…Chirality in molecular complexes has been exploited as a means to confer conformational and site-specificity in photosensitizer labeling of proteins. For example, site-dependent stereoselectivity has been observed in the labeling redox proteins with ruthenium (II) polypyridine complexes and was applied to both heme proteins (Dmochowski et al 2000;Luo et al 1998) and proteolytic enzymes (Haquette et al 2010). These studies demonstrate that complementary geometric shapes and non-covalent interactions within a protein binding pocket can be used to create a conformationally determined, lock-and-key specificity for photosensitizer integration within protein host matrices.…”

Controlling the optical and catalytic properties of artificial metalloenzyme photocatalysts using chemogenetic engineering

“…The λ max values in the absorbance and emission spectra of the cofactors did not change significantly upon bioconjugation (Supplementary Figure 4-5), consistent with the fact that the orbital energies of Ru(Bpy) 3 2+ and related complexes are generally not sensitive to changes in solvent/environment 46 . The luminescence lifetimes of the ArMs were also evaluated since it is known that the lifetime of luminophores like Ru(Bpy) 3 2+ increases in more hydrophobic environments, 30,47,48 such as that expected within the POP active site, and substantial increases compared to the free complexes were observed (Table 1). Finally, CD spectroscopy was used to more directly interrogate possible interactions between 1a-f and the different protein scaffolds (Figure 2C and Supplementary Figure 6).…”

“…Importantly, in these cases, the metal polypyridine complexes were solvent exposed, often residing in shallow clefts with limited capacity to interact with the cofactor. While changes in the photophysical or redox properties of the protein-linked complexes were reported in these examples [20][21][22][23][24][25][26][27][28][29] and others [30][31][32][33] , none of these systems were used as photocatalysts for direct transformations of organic substrates.…”

Electrochemical characterization of the artificial metalloenzyme papain-[(η6-arene)Ru(1,10-phenanthroline)Cl]+

“…Artificial metalloenzymes are constructed by incorporation of a synthetic, catalytically competent metallo-cofactor into a protein scaffold [23]. Embedding of (arene)ruthenium(N^N) complexes to the protein hosts (strept)avidin [24][25][26], papain [1,[27][28][29], carbonic anhydrase [30] or -lactoglobulin [31] following covalent or supramolecular anchoring strategies afforded artificial metalloenzymes catalyzing (asymmetric) transfer hydrogenation of ketones and reduction of NAD(P) + in aqueous medium. In addition, covalent anchoring of an [(arene)Ru(phen)Cl] + complex to papain afforded a bioconjugate displaying catalytic activity on the Lewis acid-catalyzed Diels-Alder reaction between cyclopentadiene and acrolein in water [32].…”