A selective luminescent probe for the direct time-gated detection of adenosine triphosphate

Stable Europium(III) Complexes with Short Linkers for Site-Specific Labeling of Biomolecules

In this study, two new terpyridine-based Eu^III complexes were synthesized, the structures of which were optimized for luminescence resonance energy-transfer (LRET) experiments. The complexes showed high quantum yields (32 %); a single long lifetime (1.25 ms), which was not influenced by coupling to protein; very high stability in the presence of chelators such as ethylenediamine-N,N,N',N'-tetraacetate and ethylene glycol-bis(2-aminoethylether)-N,N,N',N'-tetraacetic acid; and no interaction with cofactors such as adenosine triphosphate and guanosine triphosphate. A special feature is the short length of the linker between the Eu^III ion and the maleimide or hydrazide function, which allows for site-specific coupling of cysteine mutants or unnatural keto amino acids. As a consequence, the new complexes appear particularly suited for accurate distance measurements in biomolecules by LRET.

A metal-free fluorescence turn-on molecular probe for detection of nucleoside triphosphates

We report a fluorescence probe 1, which contains a naphthalimide fluorophore with two symmetric peptidic arms equipped with a tailor-made anion-binding motif, the guanidiniocarbonyl pyrrole moiety, for the detection of nucleoside triphosphates. Upon binding to nucleoside triphosphates, especially ATP, 1 shows significant turn-on fluorescence response. Probe 1 can also be applied for the imaging of ATP in cells.

Gadolinium Complex for the Catch and Release of Phosphate from Water

The ability of complexes of hard and labile metal ions with one or more open coordination sites to capture phosphates with high affinity and selectivity directly in water at neutral pH and release them under acidic conditions is evaluated with Gadolinium- 2,2',2''-(((nitrilotris(ethane-2,1-diyl))tris(azanediyl))tris(carbonyl))tris(4-oxo-4H-pyran-3-olate) (Gd-TREN-MAM). This model lanthanide complex has two open coordination sites that, at neutral pH, are filled with water molecules. In water at neutral pH, Gd-TREN-MAM binds phosphate with high affinity (K_a = 1.3 × 10⁴) via the formation of a ternary complex in which one phosphate replaces both inner-sphere water molecules. The formation of this complex is highly pH-dependent; the phosphate is completely released from Gd-TREN-MAM below pH 2. Because the Gd^III ion remains complexed by its ligand, even under strong acidic conditions, Gd-TREN-MAM can be used at least 10 times in a pH-based recycling scheme that enables the catch and release of one phosphate per cycle. Gd-TREN-MAM is highly selective for phosphate over other anions of environmental concerns, including HCO₃^-, HCO₂^-, CH₃CO₂^-, SO₄^2-, NO₃^-, NO₂^-, BrO₃^-, AsO₄^-, F^-, Cl^-, and Br^- and, to a lesser extent, ClO₃^-. The development of such receptors that bind phosphate reversibly in a pH-dependent manner opens the possibility to design catch-and-release systems for the purification of surface waters.

Mitochondria Targeted Nanoscale Zeolitic Imidazole Framework-90 for ATP Imaging in Live Cells

Zeolitic imidazole frameworks (ZIFs) are an emerging class of functional porous materials with promising biomedical applications such as molecular sensing and intracellular drug delivery. We report herein the first example of using nanoscale ZIFs (i.e., ZIF-90), self-assembled from Zn²⁺ and imidazole-2-carboxyaldehyde, to target subcellular mitochondria and image dynamics of mitochondrial ATP in live cells. Encapsulation of fluorescent Rhodamine B (RhB) into ZIF-90 suppresses the emission of RhB, while the competitive coordination between ATP and the metal node of ZIF-90 dissembles ZIFs, resulting in the release of RhB for ATP sensing. With this method, we are able to image mitochondrial ATP in live cells and study the ATP level fluctuation in cellular glycolysis and apoptosis processes. The strategy reported here could be further extended to tune nanoscale ZIFs inside live cells for targeted delivery of therapeutics to subcellular organelles for advanced biomedical applications.

Self-Assembled Tb3+ Complex Probe for Quantitative Analysis of ATP during Its Enzymatic Hydrolysis via Time-Resolved Luminescence in Vitro and in Vivo

To more accurately assess the pathways of biological systems, a probe is needed that may respond selectively to adenosine triphosphate (ATP) for both in vitro and in vivo detection modes. We have developed a luminescence probe that can provide real-time information on the extent of ATP, ADP, and AMP by virtue of the luminescence and luminescence lifetime observed from a supramolecular polymer based on a C₃ symmetrical terpyridine complex with Tb³⁺ (S1-Tb). The probe shows remarkable selective luminescence enhancement in the presence of ATP compared to other phosphate-displaying nucleotides including adenosine diphosphate (ADP), adenosine monophosphate (AMP), guanosine triphosphate (GTP), thymidine triphosphate (TTP), H₂PO₄^- (Pi), and pyrophosphate (PPi). In addition, the time-resolved luminescence lifetime and luminescence spectrum of S1-Tb could facilitate the quantitative measurement of the exact amount of ATP and similarly ADP and AMP within living cells. The time-resolved luminescence lifetime of S1-Tb could also be used to quantitatively monitor the amount of ATP, ADP, and AMP in vitro following the enzymatic hydrolysis of ATP. The long luminescence lifetime, which was observed into the millisecond range, makes this S1-Tb-based probe particularly attractive for monitoring biological ATP levels in vivo, because any short lifetime background fluorescence arising from the complex molecular environment may be easily eliminated.

Introduction of Quinolines and Isoquinolines onto Nonactivated α-C-H Bond of Tertiary Amides through a Radical Pathway

Treatment of quinolines and isoquinolines with benzoyl peroxide in tertiary amides, such as N,N-dimethylacetamide, N,N-dimethylpropionamide, and N-acetylpyrrolidine, etc., under irradiation with a Hg lamp in the temperature range of 35 °C to 40 °C gave C-C-bonded quinolines and isoquinolines bearing amide groups with high regioselectivity in good to moderate yields, respectively, under transition-metal-free conditions.

Detection of phosphate based on phosphorescence of Mn doped ZnS quantum dots combined with cerium(iii)

A simple and rapid room-temperature phosphorescence (RTP) sensor for phosphate detection was developed on the basis of Ce³⁺ modulated mercaptopropionic acid (MPA)-capped Mn-doped ZnS quantum dots (QDs).

Enabling the Triplet of Tetraphenylethene to Sensitize the Excited State of Europium(III) for Protein Detection and Time-Resolved Luminescence Imaging

A tetraphenylethene (TPE) group that exhibits aggregation-induced emission is incorporated into the ligand of a Eu(III) complex (TPEEu) to sensitize the excited state of Eu(III). In steady-state measurements, TPEEu exhibits weak luminescence when dissolved in aqueous solutions even at a high concentration level, but emits strong fluorescence of TPE and phosphorescence of Eu(III) upon binding with bovine serum albumin. With a delay time of 0.05 ms and a gate time of 1.0 ms in time-resolved measurements, only phosphorescent emission of Eu(III) is observed with a high on/off ratio. Moreover, this probe is successfully used in time-resolved luminescence imaging to eliminate the background signal from biological autofluorescence without a washing process. This work provides a general strategy in designing Ln(III) complexes for detecting a broad range of biological molecules.

Selective Sensing of Tyrosine Phosphorylation in Peptides Using Terbium(III) Complexes

Phosphorylation of tyrosine residues in proteins, as well as their dephosphorylation, is closely related to various diseases. However, this phosphorylation is usually accompanied by more abundant phosphorylation of serine and threonine residues in the proteins and covers only 0.05% of the total phosphorylation. Accordingly, highly selective detection of phosphorylated tyrosine in proteins is an urgent subject. In this review, recent developments in this field are described. Monomeric and binuclear Tb(III) complexes, which emit notable luminescence only in the presence of phosphotyrosine (pTyr), have been developed. There, the benzene ring of pTyr functions as an antenna and transfers its photoexcitation energy to the Tb(III) ion as the emission center. Even in the coexistence of phosphoserine (pSer) and phosphothreonine (pThr), pTyr can be efficintly detected with high selectivity. Simply by adding these Tb(III) complexes to the solutions, phosphorylation of tyrosine in peptides by protein tyrosine kinases and dephosphorylation by protein tyrosine phosphatases can be successfully visualized in a real-time fashion. Furthermore, the activities of various inhibitors on these enzymes are quantitatively evaluated, indicating a strong potential of the method for efficient screening of eminent inhibitors from a number of candidates.

Detection of NAD(P)H-dependent enzyme activity by time-domain ratiometry of terbium luminescence

NAD(P)H-dependent oxidoreductases play important roles in biology. Recently, we reported that the luminescence lifetime of some Tb(3+) complexes is sensitive to NAD(P)H, and we used this phenomenon to detect activities of these enzymes. However, conventional time-resolved luminescence assays are susceptible to static quenchers such as ATP. Herein we describe a detection methodology that overcomes this issue: the intensity of the sample is measured twice with different delay times and the intensity ratio value is used as an index of NAD(P)H concentration. The method is more robust than single-point measurement, and is compatible with high-throughput assays using conventional microplate readers.

Detection of NAD(P)H-dependent enzyme activity with dynamic luminescence quenching of terbium complexes

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.

A Multisite-Binding Switchable Fluorescent Probe for Monitoring Mitochondrial ATP Level Fluctuation in Live Cells

Adenosine triphosphate (ATP), commonly produced in mitochondria, is required by almost all the living organisms; thus fluorescent probes for monitoring mitochondrial ATP levels fluctuation are essential and highly desired. Herein, we report a multisite-binding switchable fluorescent probe, ATP-Red 1, which selectively and rapidly responds to intracellular concentrations of ATP. Live-cell imaging indicated that ATP-Red 1 mainly localized to mitochondria with good biocompatibility and membrane penetration. In particular, with the help of ATP-Red 1, we successfully observed not only the decreased mitochondrial ATP levels in the presence of KCN and starvation state, but also the increased mitochondrial ATP levels in the early stage of cell apoptosis. These results indicate that ATP-Red 1 is a useful tool for investigating ATP-relevant biological processes.

Multicolored, Tb³⁺-Based Antibody-Free Detection of Multiple Tyrosine Kinase Activities

Kinase signaling is a major mechanism driving many cancers. While many inhibitors have been developed and are employed in the clinic, resistance due to crosstalk and pathway reprogramming is an emerging problem. High-throughput assays to detect multiple pathway kinases simultaneously could better model these complex relationships and enable drug development to combat this type of resistance. We developed a strategy to take advantage of time-resolved luminescence of Tb(3+)-chelated phosphotyrosine-containing peptides, which facilitated efficient energy transfer to small molecule fluorophores conjugated to the peptides to produce orthogonally colored biosensors for two different kinases. This enabled multiplexed detection with high signal-to-noise in a high-throughput-compatible format. This proof-of-concept study provides a platform that could be applied to other lanthanide metal and fluorophore combinations to achieve even greater multiplexing without the need for phosphospecific antibodies.

Time-resolved probes and oxidase-based biosensors using terbium(III)-guanosine monophosphate-mercury(II) coordination polymer nanoparticles

A novel lanthanide coordination polymer nanoparticle (LCPN)-based ternary complex was synthesized via the self-assembly of a terbium ion (Tb(3+)) with a nucleotide (GMP) and a mercury ion (Hg(2+)) in aqueous solution. The as-prepared LCPN-based ternary complex (Tb-GMP-Hg) can be applied to the development of time-resolved luminescence assays and oxidase-based biosensors.

A fluorescent probe for estimation of adenosine diphosphate and monitoring of glucose metabolism

An ADP selective fluorescent probe working in aqueous medium was identified and the change in fluorescence as a function of ADP concentration was standardized. Using this probe, all the steps of glycolysis coupled with ATP/ADP inter-conversion and oxidative breakdown of pyruvate in the mitochondria were monitored and the consumption/production of ATP/ADP at each step was quantified. The quantity of ADP present in the mitochondria, taken from different body parts of a pig, was also determined. It is hypothesized that an appropriate modification of the technique may provide a diagnostic tool for monitoring biochemical pathways as well as for quick estimation of ADP in the mitochondria and other cell organelles.

A terbium(III)-complex-based on-off fluorescent chemosensor for phosphate anions in aqueous solution and its application in molecular logic gates

A new Tb(III) complex based on a tripodal carboxylate ligand has been synthesized for the selective fluorescent recognition of phosphate anions, including inorganic phosphates and nucleoside phosphates (e.g., ATP), in Tris buffer solution. The resulting L · Tb complex shows the characteristic emission bands centered at about 495 and 550 nm from the Tb(III)-centered (5)D4 excited state to (7)FJ transitions with J = 6 and 5, where the chelating ligand acts only as an "antenna". Upon the addition of phosphate anions to the aqueous solution of Tb(III) complex, significant "on-off" fluorescence changes were observed, which were attributed to the inhibition of the "antenna" effect between the ligand and Tb(III) after the incorporation of phosphate anions. Furthermore, this unique Tb(III) complex has been successfully utilized to detect phosphate anions with filter papers and hydrogels. Notably, the Tb(III) complex also can be used for the construction of molecular logic gates with TRANSFER and INHIBIT logic functions by using the above fluorescence changes.

Exploitation and application of a highly sensitive Ru(II) complex-based phosphorescent chemodosimeter for Hg2+ in aqueous solutions and living cells

A novel Ru(II) complex-based phosphorescent probe Rubpy-1 was designed and synthesized conveniently by incorporating of chemodosimeter into the luminophor, which exhibits good water solubility, longer excitation wavelength, and rapid turn-on phosphorescent response only toward Hg(2+) in aqueous system under physiological pH. The spectral response mechanism and Hg(2+)-promoted structure change of the chemodosimeter were analyzed in detail by theoretical calculations and electrospray ionization mass spectrometry. When time-resolved photoluminescence techniques were used, the Rubpy-1 could eliminate effectively the signal interference from the short-lived background fluorescence in complicated media, accompanied by the significant improvement of the signal-to-noise ratio and the accuracy of the detection. Furthermore, Rubpy-1 showed low cytotoxicity and excellent membrane permeability toward living cells, which was successfully applied to monitor intracellular Hg(2+) effectively by confocal luminescence imaging.

A macrocyclic tetraamine bearing four phenol groups: a new class of heptadentate ligands to provide an oxygen-sensitive luminescent Tb(iii) complex with an extendable phenol pendant arm

The potentially N₄O₄-octadentate ligand unprecedentedly coordinates to the Tb³⁺ion in a N₄O₃-heptadentate fashion and provides a highly luminescent and highly oxygen-sensitive terbium(iii) complex.

Tb(III)-doped silica nanoparticles for sensing: effect of interfacial interactions on substrate-induced luminescent response

The present work introduces the easy modification of the water-in-oil microemulsion procedure aimed at the doping of the Tb(III) complexes within core or shell zones of the silica nanoparticles (SNs), which are designated as "core-shell", "shell", and "core". The dye molecules, chelating ligands, and copper ions were applied as the quenchers of Tb(III)-centered luminescence through dynamic or/and static mechanisms. The binding of the quenchers at the silica/water interface results in the quenching of the Tb(III) complexes within SNs, which, in turn, is greatly dependent on the synthetic procedure. The luminescence of "core" SNs remains unchanged under the binding of the quenchers at the silica/water interface. The quenching through dynamic mechanism is more significant for "core-shell" and "shell" than for "core" SNs. Thus, both "core-shell" and "shell" SNs have enough percentage of the Tb(III) complexes located close to the interface for efficient quenching through the energy transfer. The quenching through the ion or ligand exchange is most efficient for "core-shell" SNs due to the greatest percentage of the Tb(III) complexes at the silica/water interface, which correlates with the used synthetic procedure. The highlighted regularities introduce the applicability of "core-shell" SNs used as silica beads for phosphatidylcholine bilayers in sensing their permeability toward the quenching ions.

Turning an aptamer into a light-switch probe with a single bioconjugation

We describe a method for transforming a structure-switching aptamer into a luminescent light-switch probe via a single conjugation. The methodology is demonstrated using a known aptamer for Hg²⁺ as a case study. This approach utilizes a lanthanide-based metallointercalator, Eu-DOTA-Phen, whose luminescence is quenched almost entirely and selectively by purines, but not at all by pyrimidines. This complex, therefore, does not luminesce while intercalated in dsDNA, but it is bright red when conjugated to a ssDNA that is terminated by several pyrimidines. In its design, the light-switch probe incorporates a structure-switching aptamer partially hybridized to its complementary strand. The lanthanide complex is conjugated to either strand via a stable amide bond. Binding of the analyte by the structure-switching aptamer releases the complementary strand. This release precludes intercalation of the intercalator in dsDNA, which switches on its luminescence. The resulting probe turns on 21-fold upon binding to its analyte. Moreover, the structure switching aptamer is highly selective, and the long luminescence lifetime of the probe readily enables time-gating experiments for removal of the background autofluorescence of the sample.

A Ga(3+)self-assembled fluorescent probe for ATP imaging in vivo

Adenosine 5'-triphosphate (ATP) is a functional molecule associated with many important biological processes. Fluorescent detection methods for ATP with facile performance and high selectivity are in demand. One of the possible multi-membered arrays assembled between DHBO and Ga(3+) ions was conducted in aqueous solution, which can selectively recognize ATP with fluorescence enhancement from ADP, AMP and other structurally similar nucleoside triphosphates in vitro and in vivo. ATP facilitates the interaction between DHBO and Ga(3+) ions, resulting in the fluorescence increase. The detection limit for ATP was calculated to be 5.49×10(-7)M, which is much lower than that of intracellular concentrations (1-10mM). In addition, DHBO-Ga(3+) can be applied to detect ATP-relevant enzyme activity.

Effect of lanthanide complex structure on cell viability and association

A systematic study of the effect of hydrophobicity and charge on the cell viability and cell association of lanthanide metal complexes is presented. The terbium luminescent probes feature a macrocyclic polyaminocarboxylate ligand (DOTA) in which the hydrophobicity of the antenna and that of the carboxyamide pendant arms are independently varied. Three sensitizing antennas were investigated in terms of their function in vitro: 2-methoxyisophthalamide (IAM(OMe)), 2-hydroxyisophthalamide (IAM), and 6-methylphenanthridine (Phen). Of these complexes, Tb-DOTA-IAM exhibited the highest quantum yield, although the higher cell viability and more facile synthesis of the structurally related Tb-DOTA-IAM(OMe) platform renders it more attractive. Further modification of this latter core structure with carboxyamide arms featuring hydrophobic benzyl, hexyl, and trifluoro groups as well as hydrophilic amino acid based moieties generated a family of complexes that exhibit high cell viability (ED50 > 300 μM) regardless of the lipophilicity or the overall complex charge. Only the hexyl-substituted complex reduced cell viability to 60% in the presence of 100 μM complex. Additionally, cellular association was investigated by ICP-MS and fluorescence microscopy. Surprisingly, the hydrophobic moieties did not increase cell association in comparison to the hydrophilic amino acid derivatives. It is thus postulated that the hydrophilic nature of the 2-methoxyisophthalamide antenna (IAM(OMe)) disfavors the cellular association of these complexes. As such, responsive luminescent probes based on this scaffold would be appropriate for the detection of extracellular species.

Discrimination of adenine nucleotides and pyrophosphate in water by a zinc complex of an anthracene-based cyclophane

Combining metal-anion coordination and π-π stacking interactions, a zinc complex of a novel anthracene-based cyclophane was designed to recognise adenine nucleoside polyphosphates. This complex was found to show selective fluorescence enhancement for ATP, ADP, AMP and PPi in neutral aqueous solution. Among them, ADP induced the largest fluorescence change to the complex, while ATP showed the strongest binding affinity to the complex. This property was used to sense ATP in the presence of excess amounts of other phosphates such as ADP, AMP, PPi and Pi.

Sensing of phosphates by using luminescent Eu(III) and Tb(III) complexes: application to the microalgal cell Chlorella vulgaris

Phenanthroline-based chiral ligands L(1) and L(2) as well as the corresponding Eu(III) and Tb(III) complexes were synthesized and characterized. The coordination compounds show red and green emission, which was explored for the sensing of a series of anions such as F(-), Cl(-), Br(-), I(-), NO3(-), NO2(-), HPO4(2-), HSO4(-), CH3COO(-), and HCO3(-). Among the anions, HPO4(2-) exhibited a strong response in the emission property of both europium(III) and terbium(III) complexes. The complexes showed interactions with the nucleoside phosphates adenosine triphosphate (ATP), adenosine diphosphate (ADP), and adenosine monophosphate (AMP). Owing to this recognition, these complexes have been applied as staining agents in the microalgal cell Chlorella vulgaris. The stained microalgal cells were monitored through fluorescence microscopy and scanning electron microscopy. Initially, the complexes bind to the outer cell wall and then enter the cell wall through holes in which they probably bind to phospholipids. This leads to a quenching of the luminescence properties.

Naphthyridine-based lanthanide complexes worked as magnetic resonance imaging contrast for guanosine 5'-monophosphate in vivo

New lanthanide complex Gd-ANAMD containing 2-amino-7-methyl-1,8-naphthyridine was achieved for selective magnetic resonance imaging towards guanosine 5'-monophosphate over other ribonucleotide polyphosphates in aqueous media and in vivo. The formation of strong multi-hydrogen bonds between naphthyridine and guanosine made the phosphate in guanosine 5'-monophosphate positioned on a suitable site to coordinate with the lanthanide ion. The substitution of the coordination naphthyridine by the phosphate oxygen atoms caused obvious relaxivity decrease. The negligible cytotoxicity and appropriate blood circulation time of Gd-ANAMD allow potential application of Magnetic Resonance Imaging in vivo. (1)H NMR confirmed that the selectivity of these lanthanide complexes towards guanosine was attributed to the formation of hydrogen bonds between the guanine moeity and the naphthyridine. The fluorescence detection and lifetime measurement of Tb-ANAMD and Eu-ANAMD suggested that the decrease of the relaxivity is not attributed to the change of the q value, but caused by the prolonging of the residence lifetime of inner-sphere water.

Basis for sensitive and selective time-delayed luminescence detection of hydroxyl radical by lanthanide complexes

Molecular probes for the detection of hydroxyl radical (HO•) by time-delayed luminescence spectroscopy directly in water at neutral pH with high sensitivity and selectivity are presented. The bimolecular probes consist of a lanthanide complex with open coordination sites and a reactive pre-antenna composed of an aromatic acid or amide; the latter binds to and sensitizes terbium emission upon hydroxylation by HO•. These probes exhibit long luminescence lifetimes compatible with time-delayed measurements that remove interfering background fluorescence from the sample. Six different reactive pre-antenna (benzoate, benzamide, isophthalate, isophthalamide, trimesate, and trimesamide) and two different terbium complexes [Tb-(1,4,7,10-tetraazacyclododecane-1,4,7-tris(acetic acid)) (Tb-DO3A) and Tb-(1,4,7,10-tetraazacyclododecane-1,7-bis(acetic acid)) (Tb-DO2A)] were evaluated. Of these the trimesamide/Tb-DO3A system enables the most sensitive detection of HO• with an about 1000-fold increase in metal-centered time-delayed emission upon hydroxylation of the pre-antenna to 2-hydroxytrimesamide. Excellent selectivity for both the trimesamide/Tb-DO3A and trimesate/Tb-DO3A systems over other reactive oxygen and nitrogen species are observed. Notably, the increase in metal-centered luminescence intensity is not associated with a decrease in the hydration number (q) of Tb-DO3A, suggesting that the antenna is interacting with the lanthanide via a second sphere coordination environment or that coordination by the antenna occurs by displacement of one or more of the carboxylate arms of DO3A. Formation of a weak ternary complex Tb-DO3A•hydroxytrimesamide was confirmed by temperature-dependent titration and a decrease in K(app) with increasing temperature.

Magnetoluminescent light switches--dual modality in DNA detection

The synthesis and properties of two responsive magnetoluminescent iron oxide nanoparticles for dual detection of DNA by MRI and luminescence spectroscopy are presented. These magnetoluminescent agents consist of iron oxide nanoparticles conjugated with metallointercalators via a polyethylene glycol linker. Two metallointercalators were investigated: Ru(bpy')(phen)(dppz), which turns on upon DNA intercalation, and Eu-DOTA-Phen, which turns off. The characteristic light-switch responses of the metallointercalators are not affected by the iron oxide nanoparticles; upon binding to DNA the luminescence of the ruthenium complexes increases by ca. 20-fold, whereas that of the europium complex is >95% quenched. Additionally, the 17-20 nm magnetite cores, having permeable PEG coatings and stable dopamide anchors, render the two constructs efficient responsive contrast agents for MRI with unbound longitudinal and transverse relaxivities of 12.4-9.2 and 135-128 mM(-1)(Fe)s(-1), respectively. Intercalation of the metal complexes in DNA results in the formation of large clusters of nanoparticles with a resultant decrease of both r1 and r2 by 32-63% and 24-38%, respectively. The potential application of these responsive magnetoluminescent assemblies and their reversible catch-and-release properties for the purification of DNA is presented.

An ATP-selective, lanthanide complex luminescent probe

A luminescent probe based on a europium complex is developed, which effectively distinguishes adenosine-5'-triphosphate (ATP) from adenosine diphosphate (ADP) and adenosine monophosphate (AMP) in pure water at pH 6.8. With a longer lifetime (in ms range), the probe is prospectively applied to biological systems to monitor ATP levels by completely removing the background fluorescence of other molecules.