title: Real time detection of cell cycle regulator cyclin A on living tumor cells with europium emission.
abstract: Six water-soluble europium complexes (Eu-L1-P(n) and Eu-L2-P(n), n = 1, 2 and 3) with one antenna chromophore, two different linkers (L1 and L2) and three proposed cyclin A specific peptides (P1: -GAKRRLIF-NH2; P2: -GGAKRRLIF-NH2; P3: -Hex- GAKRRLIF-NH2) have been synthesized. With structural information available, comparisons of the cyclin grooves of cyclin A and the six europium complexes have been made, and insights have been gained into the determinants for peptide binding and the foundation of differential binding. Experiment-wise, the linear and two-photon induced photophysical properties of these conjugates were monitored in aqueous solution. Numerous in situ/in vitro biological assays have been carried out, such as responsive emission changes in situ/in vitro, Western blot and cellular uptake. As imaging agents, complexes with peptides P3: -Hex-GAKRRLIF-NH2 showed high selectivity to cyclin A in numerous cancer cells. When it comes to responsive optical signal changes, complex Eu-L2-P3 exhibited a threefold emission enhancement upon binding with cyclin A (100 nM cyclin A, ϕ = 8% to 21%, log KB = 5.83, detection limit = 5 nM), and this could be initiated by the shortened distance between the antenna and the lanthanide after they bind/get into cyclin A. It is promising that our compounds (especially compound Eu-L2-P3) could serve as the template for structure-guided efforts to develop potential imaging therapeutics on the basis of selective imaging of CDK2/cyclin A activity.
authors.affiliation: Department of Chemistry, Hong Kong Baptist University, Kowloon Tong, Kowloon, Hong Kong.
authors.forename: Hongguang
authors.initials: H
authors.lastname: Li
authors.forename: Frances L
authors.initials: FL
authors.lastname: Chadbourne
authors.forename: Rongfeng
authors.initials: R
authors.lastname: Lan
authors.forename: Chi-Fai
authors.initials: CF
authors.lastname: Chan
authors.forename: Wai-Lun
authors.initials: WL
authors.lastname: Chan
authors.forename: Ga-Lai
authors.initials: GL
authors.lastname: Law
authors.forename: Chi-Sing
authors.initials: CS
authors.lastname: Lee
authors.forename: Steven L
authors.initials: SL
authors.lastname: Cobb
authors.forename: Ka-Leung
authors.initials: KL
authors.lastname: Wong
mesh_terms: D002453:Cell Cycle; D019925:Cyclin A / Q000032:analysis*; D005063:Europium / Q000737:chemistry*; D006367:HeLa Cells; D006801:Humans; D008958:Models, Molecular; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry* / Q000493:pharmacokinetics; D013997:Time Factors
chemical_list: D019925:Cyclin A; D009942:Organometallic Compounds; D005063:Europium