title: Rhenium(I) polypyridine dibenzocyclooctyne complexes as phosphorescent bioorthogonal probes: Synthesis, characterization, emissive behavior, and biolabeling properties.
abstract: We report the development of rhenium(I) polypyridine complexes appended with a dibenzocyclooctyne (DIBO) moiety as bioorthogonal probes for azide-modified biomolecules. Three phosphorescent rhenium(I) polypyridine DIBO complexes [Re(N^N)(CO)3(py-C6-DIBO)][CF3SO3] (py-C6-DIBO=3-(N-(6-(3,4:7,8-dibenzocyclooctyne-5-oxycarbonylamino)hexyl)aminocarbonyl)pyridine; N^N=1,10-phenanthroline (phen) (1a), 3,4,7,8-tetramethyl-1,10-phenanthroline (Me4-phen) (2a), 4,7-diphenyl-1,10-phenanthroline (Ph2-phen) (3a)) and their DIBO-free counterparts [Re(N^N)(CO)3(py-C6-BOC)][CF3SO3] (py-C6-BOC=3-(N-(6-(tert-butoxycarbonylamino)hexyl)aminocarbonyl)pyridine; N^N=phen (1b), Me4-phen (2b), Ph2-phen (3b)) were synthesized and characterized. Upon photoexcitation, all the complexes displayed intense and long-lived yellow triplet metal-to-ligand charge-transfer ((3)MLCT) (dπ(Re)→π*(N^N)) emission. The DIBO complexes underwent facile reactions with benzyl azide in methanol at 298 K with second-order rate constants (k2) in the range of 0.077 to 0.091 M(-1) s(-1). As revealed from SDS-PAGE analysis, the DIBO complexes can selectively label azide-modified proteins and the resulting bioconjugates displayed strong phosphorescence upon photoexcitation. Results of inductively coupled plasma mass spectrometry (ICP-MS) and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays indicated that the DIBO complexes accumulated in Chinese Hamster Ovary (CHO) cells with considerable cytotoxic activity. Upon incubation of CHO cells with these complexes, relatively weak intracellular emission was observed. In contrast, upon pretreatment of the cells with 1,3,4,6-tetra-O-acetyl-N-azidoacetyl-D-mannosamine (Ac4ManNAz), intense emission was observed from the cell membrane and some internal compartments. The results suggest that the DIBO complexes are promising candidates for imaging azide-labeled biomolecules.
authors: Department of Biology and Chemistry, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, People's Republic of China.
authors: Alex Wing-Tat
authors: AW
authors: Choi
authors: Department of Biology and Chemistry, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, People's Republic of China.
authors: Hua-Wei
authors: HW
authors: Liu
authors: Department of Biology and Chemistry, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, People's Republic of China. Electronic address: bhkenlo@cityu.edu.hk.
authors: Kenneth Kam-Wing
authors: KK
authors: Lo
mesh_terms: D051696:Activating Transcription Factors / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D016466:CHO Cells; D002417:Cattle; D002470:Cell Survival / Q000187:drug effects; D006224:Cricetinae; D003412:Cricetulus; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D020128:Inhibitory Concentration 50; D049449:Luminescence; D018613:Microscopy, Confocal; D008956:Models, Chemical; D015335:Molecular Probes / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology; D011485:Protein Binding; D012211:Rhenium / Q000737:chemistry* / Q000378:metabolism; D012709:Serum Albumin / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D012710:Serum Albumin, Bovine / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology
chemical_list: D051696:Activating Transcription Factors; D015335:Molecular Probes; D009942:Organometallic Compounds; D012709:Serum Albumin; D012710:Serum Albumin, Bovine; D012211:Rhenium
keywords: Bioorthogonal; Imaging agents; Phosphorescence; Rhenium; Sensors