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Optochemical tools that can modulate the activity of the target protein provide an opportunity for studying and regulating the related biological processes. Here we present a DNA-based nongenetic optochemical tool that can control the dynamics of growth factor signaling. This photo-caged mimicry of growth factor can be a promising tool for elucidating a linkage between the dynamics of signaling and the resulting biological outcomes, as well as for manipulating cellular functions and the fate of living cells.

We have designed and developed non-fluorescent, cell-permeable photoactivatable fluorophores, photoactivatable SPiDERs (paSPiDERs), which exhibit fluorescence activation upon light irradiation, accompanied by the generation of a quinone methide intermediate that binds covalently to intracellular proteins. The fluorescence signal is durable for 24 hours, resistant to fixation and compatible with immunostaining, and selective cell labeling can be achieved at single-cell resolution.

Spontaneously blinking fluorophores are powerful tools for live-cell super-resolution imaging under physiological conditions. Here we show that quantum-chemical calculations can predict key parameters for fluorophore design. We applied this methodology to develop a spontaneously blinking fluorophore with yellow fluorescence for super-resolution imaging of microtubules in living cells.

We show that the equilibrium of intramolecular spirocyclization of coumarin-hemicyanine hybrid fluorophores can be finely tuned by means of chemical modifications. We used this scaffold to develop activatable fluorescent probes with large Stokes shifts for γ-glutamyltranspeptidase and esterase.

Si-Rhodamines are bright fluorophores with red to near-infrared (NIR) emission, and are widely used for fluorescence imaging of biological phenomena. Here, in order to extend the scope of Si-rhodamine fluorophores, we established a versatile synthesis of unsymmetrical Si-rhodamines. To illustrate its value, we used one of these new fluorophores to synthesize a far-red to NIR fluorescence probe for hypoxia, and showed that it can visualize hepatic ischemia in mice in vivo.

We have developed the first green-light-emitting, spontaneously blinking fluorophore (SBF), HEtetTFER. In combination with our near-infrared-light-emitting SBF (HMSiR), HEtetTFER allows dual-colour single-molecule localization microscopy (SMLM) in buffer solution without any additive and without photoactivation.

We report a reversible off/on fluorescent probe for monitoring concentration changes of sulfane sulfur by utilizing the unique ability of sulfane sulfur to bind reversibly to other sulfur atoms and the intramolecular spirocyclization reaction of xanthene dyes. It reversibly visualized sulfane sulfur in living A549 cells and primary-cultured hippocampal astrocytes.

We employed a fluorescent substrate-based target discovery approach to screen the enzymome for metabolic activity towards pyruvyl-amidated peptides, and identified an acylamino acid-releasing enzyme (APEH). Cells overexpressing APEH exhibited higher metabolic activity towards the probe, N-pyruvyl-leucyl-7-amido-4-methylcoumarin (Pyr-Leu-AMC), while the selective APEH inhibitor AA74-1 blocked the reaction. Metabolism of various pyruvylated peptides in liver lysate was almost completely blocked by AA74-1. Pyruvyl peptides are synthesized in response to oxidative stress, but their biological role is poorly understood; identification of a key contributor to their metabolism should stimulate research on pathways leading from oxidative stress to protein modification and biological output.

We discovered that positively charged terbium complexes bearing 1,4,7,10-tetraazacyclododecane functionalized with amide ligands are highly sensitive to dynamic luminescence quenching by NAD(P)H. We exploited this phenomenon to establish a general time-resolved luminescence-based assay platform for sensitive detection of NAD(P)H-dependent enzyme activities.

We have developed a small-molecular probe, consisting of cyclic RGD pentapeptides bearing a nitrobenzoxadiazole fluorophore at the 4'-residue, which detects integrin αVβ3 activity in terms of fluorescence intensity decrease due to quenching of the fluorophore by interaction with tyrosine-122 at the binding site of the protein. This probe appears to be suitable for a practical, high-throughput fluorescence assay to screen small-molecular modulators of integrin activity.

Acrolein, a cytotoxic α,β-unsaturated aldehyde and disease biomarker, was determined in plasma by means of a novel tethering strategy using Michael addition of the compound to a fluorescent dye, followed by immobilization of the product on microbeads via the aldehyde moiety. Elevation of blood acrolein was detected in mice treated with an anticancer agent cyclophosphamide, which releases acrolein upon activation. This method should be suitable for high-throughput diagnostic and clinical application.

In this proof-of-concept study, a new activatable imaging agent based on two luminophores and two different quenching mechanisms is reported. Both partial and total activation of the luminescence signal can be achieved, either in solution or in vitro. Bond cleavage makes the compound suitable for luminescence lifetime imaging.

TokyoGreen (TG) derivatives were found to be efficient and specific substrates of an important drug-metabolizing enzyme, UDP-glucuronosyltransferase (UGT) 1A1. A rapid, specific, and sensitive assay of the enzyme was achieved simply by monitoring the change in fluorescence intensity. We also designed and developed the first "turn-on" fluorescent probes for UGTs.

We have designed and synthesized a reversible near-infrared (NIR) fluorescence probe, 2-Me TeR, for reactive oxygen species (ROS), utilizing the redox properties of the tellurium (Te) atom. 2-Me TeR is oxidized to fluorescent 2-Me TeOR by various ROS, while the generated 2-Me TeOR is quickly reduced in the presence of glutathione to regenerate 2-Me TeR. This redox-induced reversible NIR-fluorescence response of 2-Me TeR allowed us to detect the endogenous production of ROS and subsequent homeostatic recovery of the intracellular reductive environment in hydrogen peroxide-stimulated HL-60 cells. This probe is expected to be useful for monitoring the dynamics of ROS production continuously in vivo.

Luminescent lanthanide complexes incorporating Yb(3+) and Nd(3+) are attracting much attention as imaging agents, but there have been few practical methods to make responsive sensors with these complexes. Here, we introduce a general strategy to synthesize near-infrared luminescent probes by conjugating a Yb(3+) chelate to established fluorescein-based probes. As the first demonstration, we present a complex, based on the green-emitting probe DAF-4, that responds to nitric oxide (NO) in aqueous solution with a significant increase in luminescence intensity at 980 nm.

Arylamine N-acetyltransferase (NAT) is an important phase II metabolizing enzyme that influences drug efficacy and adverse effects. Here, we report a long-lived luminescent lanthanide complex as a probe for NAT, employing an intraligand photoinduced electron transfer strategy. The probe shows approximately 100-fold increase of luminescence upon N-acetylation catalyzed by NAT, with relatively high specificity for NAT2 over NAT1. It is the first NAT probe that is suitable for sensitive, homogeneous, and rapid detection of NAT activity of recombinant enzyme or cell lysate, and is expected to be useful for drug discovery and clinical diagnosis., (This journal is © The Royal Society of Chemistry 2012)

We studied the photobleaching of a library of boron dipyrromethene (BODIPY) derivatives with a range of electron densities, and found that the photobleaching rate is influenced by the electron-withdrawing capacity of the substituents. Electron-deficient BODIPYs generated less singlet oxygen, were less reactive to singlet oxygen, and were highly resistant to photobleaching. We confirmed the utility of one of these fluorophores, 2,6-diCO(2)R-BDP, for visualizing EGF receptor dynamics in cells expressing an SNAP-tagged EGF receptor.

Ratiometric fluorescent probes based on boron dipyrromethene (BODIPY) were developed based on a novel design strategy, in which a change of the electron-withdrawing character of the 2,6-substituents resulting from reaction with a target molecule generates a fluorescence wavelength change.