Ruthenium(II)−Phenanthroline−Biotin Complexes:  Synthesis and Luminescence Enhancement upon Binding to Avidin

Abstract

We report the synthesis, characterization, and avidin-binding properties of two novel ruthenium complexes, [Ru(bpy)(2)(phen-biotin)][PF(6)](2) 1 and [Ru(phen)(2)(phen-biotin)][PF(6)](2) 2 (bpy = 2,2'-bipyridine; phen = 1,10-phenanthroline, phen-biotin = 5-(10-amidobiotinyl)-1,10-phenanthroline)). We demonstrate that both biotinylated compounds bind to avidin through their biotin moieties with high affinity and in a 4:1 ratio. The binding of compounds 1 and 2 to avidin results in an enhancement in luminescence intensity ( approximately 1.4x, approximately 1.6x, respectively), relative to the unbound biotinylated ruthenium complexes. This behavior is markedly different from biotinylated organic dyes, whose fluorescence is quenched upon binding to avidin. Thus, ruthenium-biotin complexes 1 and 2 can form the basis of new, simplified biotin-avidin assays, which involve luminescence detection of the relevant biotinylated molecule through cross-linking with avidin.

DNA–Protein Noncovalent Cross‐Linking: Ruthenium Dipyridophenazine Biotin Complex for the Assembly of Proteins and Gold Nanoparticles on DNA Templates

“…[29] We have previously attached phen-biotin (2) to ruthenium(II) bis-bipyridine (RuA C H T U N G T R E N N U N G (bpy)), have shown that the resulting complex displays high binding affinity to streptavidin, and that its luminescence is enhanced upon binding. [35] For the intercalating portion of the molecule, we selected dipyridophenazine (DPPZ) as an extended aromatic moiety. Ruthenium-DPPZ (Ru-A C H T U N G T R E N N U N G (dppz)) complexes have been pioneered by the laboratory of Barton et al as "molecular light switches", the luminescence of which is undetectable in water, but is turned "on" in the presence of double-stranded DNA (K d~1 0 À6 m).…”

“…Some of these complexes were shown to bind DNA and avidin in separate experiments, but cross-linking of the two molecules was not demonstrated. [36,37] 6 ] 2 ) was synthesized by coupling RuA C H T U N G T R E N N U N G (dppz) 2 Cl 2 [38] and phen-biotin (2) [35] in ethylene glycol/water, followed by precipitation with NH 4 [39] was first coupled with the acyl chloride derivative of biotin. [40] The DPPZ-biotin ligand was then treated with RuA C H T U N G T R E N N U N G (bpy) 2 Cl 2 [41] and complex 3 was obtained as a PF 6 À salt (Scheme 2).…”

“…Streptavidin was dissolved in buffer A, and its concentration was determined as described previously. [54] Ru-A C H T U N G T R E N N U N G (dppz) 2 Cl 2 , [38] phen-biotin ligand 2, [35] 7-NH 2 -DPPZ [39] were synthesized as previously described.…”

Spectroscopic characterization of chloride and pseudohalide ruthenium(II) complexes with 4-(4-nitrobenzyl)pyridine

“…Luminescent ruthenium(II) complexes are of interest of due to their applications in photochemical molecular devices (PMD) such as OLED devices, dye-sensitized solar cells (DSSC), photosensitizers in artificial photosynthesis, sensors, DNA dynamic probes, lipid probes and fluorescence polarization immunoassays (FPI) [1][2][3][4][5][6][7][8][9][10][11]. Recent descriptions of the photochemistry of coordination compounds of ruthenium(II) indicate that they can fulfill many of the functions necessary for these devices [1].…”

“…Recent descriptions of the photochemistry of coordination compounds of ruthenium(II) indicate that they can fulfill many of the functions necessary for these devices [1]. One of the most studied classes of ruthenium(II) complexes are polypyridine complexes [11][12][13][14][15]. In these species, strong emission in ambient temperature solutions is attributed to 3 MLCT states, but the photophysics and photochemistry of cationic polypyridine complexes depend also on the accessibility of short lived (s = 5 -20 ns or less) 3 MC states [1].…”