2 research outputs found
Supramolecular Au<sup>I</sup>–Cu<sup>I</sup> Complexes as New Luminescent Labels for Covalent Bioconjugation
Two new supramolecular organometallic
complexes, namely, [Au<sub>6</sub>Cu<sub>2</sub>(C<sub>2</sub>C<sub>6</sub>H<sub>4</sub><b>CHO</b>)<sub>6</sub>(PPh<sub>2</sub>C<sub>6</sub>H<sub>4</sub>PPh<sub>2</sub>)<sub>3</sub>]Â(PF<sub>6</sub>)<sub>2</sub> and [Au<sub>6</sub>Cu<sub>2</sub>(C<sub>2</sub>C<sub>6</sub>H<sub>4</sub><b>NCS</b>)<sub>6</sub>(PPh<sub>2</sub>C<sub>6</sub>H<sub>4</sub>PPh<sub>2</sub>)<sub>3</sub>]Â(PF<sub>6</sub>)<sub>2</sub>, with highly
reactive aldehyde and isothiocyanate groups have been synthesized
and characterized using X-ray crystallography, ESI mass spectrometry,
and NMR spectroscopy. The compounds obtained demonstrated bright emission
in solution with the excited-state lifetime in microsecond domain
both under single- and two-photon excitation. The luminescent complexes
were found to be suitable for bioconjugation in aqueous media. In
particular, they are able to form the covalent conjugates with proteins
of different molecular size (soybean trypsin inhibitor, human serum
albumin, rabbit anti-HSA antibodies). The conjugates demonstrated
a high level of the phosphorescent emission from the covalently bound
label, excellent solubility, and high stability in physiological media.
The highest quantum yield, storage stability, and luminance were detected
for bioconjugates formed by covalent attachment of the aldehyde-bearing
supramolecular Au<sup>I</sup>–Cu<sup>I</sup> complex. The measured
biological activity of one of the labeled model proteins clearly showed
that introduced label did not prevent the biorecognition and specific
protein–protein complex formation that was extremely important
for the application of the conjugates in biomolecular detection and
imaging
Coordination to Imidazole Ring Switches on Phosphorescence of Platinum Cyclometalated Complexes: The Route to Selective Labeling of Peptides and Proteins via Histidine Residues
In this study, we have shown that
substitution of chloride ligand
for imidazole (Im) ring in the cyclometalated platinum complex PtÂ(phpy)Â(PPh<sub>3</sub>)Cl (<b>1</b>; phpy, 2-phenylpyridine; PPh<sub>3</sub>, triphenylphosphine), which is nonemissive in solution, switches
on phosphorescence of the resulting compound. Crystallographic and
nuclear magnetic resonance (NMR) spectroscopic studies of the substitution
product showed that the luminescence ignition is a result of Im coordination
to give the [PtÂ(phpy)Â(Im)Â(PPh<sub>3</sub>)]Cl complex. The other imidazole-containing
biomolecules, such as histidine and histidine-containing peptides
and proteins, also trigger luminescence of the substitution products.
The complex <b>1</b> proved to be highly selective toward the
imidazole ring coordination that allows site-specific labeling of
peptides and proteins with <b>1</b> using the route, which is
orthogonal to the common bioconjugation schemes via lysine, aspartic
and glutamic acids, or cysteine and does not require any preliminary
modification of a biomolecule. The utility of this approach was demonstrated
on (i) site-specific modification of the ubiquitin, a small protein
that contains only one His residue in its sequence, and (ii) preparation
of nonaggregated HSA-based Pt phosphorescent probe. The latter particles
easily internalize into the live HeLa cells and display a high potential
for live-cell phosphorescence lifetime imaging (PLIM) as well as for
advanced correlation PLIM and FLIM experiments