Terbium

The three new complexes Tp(Py)Ln(CH3CO2)2(H2O) (Ln = Eu (1), Gd(2), or Tb (3)) were prepared and characterized crystallographically. In the crystal lattices of these complexes, separate molecules are connected in infinite chains by π-stacking interactions. Complexes 1 and 3 display intense photoluminescence and triboluminescence (red and green respectively), while compound 3 exhibits electroluminescence commencing at 9 V in an ITO/PVK/3/Al device (ITO = indium-tin oxide, PVK = poly(N-vinylcarbazole)). A series of Eu/Tb-doped Gd compounds was prepared by cocrystallization from mixtures of 1 and 2 or 2 and 3, respectively. It was shown that π-stacking interactions are involved in increasing the efficiency of energy transfer from the gadolinium complex to emitting [Tp(Py)Eu](2+) or [Tp(Py)Tb](2+) centers, and this energy transfer occurs through hundreds of molecules, resembling the process of energy harvesting in chloroplast stacks.

Proteins may undergo multiple conformational changes required for their function. One strategy used to estimate target-site positions in unknown structural conformations involves single-pair resonance energy transfer (RET) distance measurements. However, interpretation of inter-residue distances is difficult when applied to three-dimensional structural rearrangements, especially in homomeric systems. We developed a positioning method using inverse trilateration/triangulation to map target sites within a homomeric protein in all defined states, with simultaneous functional recordings. The procedure accounts for probe diffusion to accurately determine the three-dimensional position and confidence region of lanthanide LRET donors attached to a target site (one per subunit), relative to a single fluorescent acceptor placed in a static site. As first application, the method is used to determine the position of a functional voltage-gated potassium channel's voltage sensor. Our results...

By means of cryoelectron transmission microscopy (cryo-TEM), we were able to demonstrate the formation of ternary complexes (TC): DNA–phosphatidylcholine liposome–divalent metal cations. Addition of Ba2+ to TC led to visualization of DNA compacting on the liposome surface. Staining the TC by Tb3+ cations revealed the changed secondary structure of DNA located between fused liposomes. Cryo-TEM and liposome turbidity data were analyzed during TC formation. Liposome aggregation and the liposome fusion induced by DNA in TC were observed. Because TC displayed the property of DNA cationic liposome complexes as well as their own unique properties, we were able to consider cationic lipoplexes as a particular case of TC. The involvement of TC and direct DNA–lipid interactions in the formation nuclear pore complexes were assumed.

DOTASQ (for DOTA-templated Synthetic G-quartet) is the first prototype of nature-inspired G-quadruplex ligand: its design, founded on a possible intramolecular G-quartet formation, enables it to interact with G-quadruplex DNA via an unprecedented nature-mimicking binding mode, based on the association between two G-quartets, one being native (quadruplex) and the other one artificial (ligand).

All lanthanides have similar chemical properties regarding labeling. Therefore, radiolanthanides that have been used for therapy, such as (153)Sm and (177)Lu, might easily be replaced with other radiolanthanides. The aim of this work was to investigate the suitability of electron- and positron-emitting radiolanthanides for radionuclide therapy with reference to dosimetry and production possibilities. Radiolanthanides with half-lives of 1 h to 15 d, stable or long-lived daughters, and limited photon emission were selected. The ratio of the absorbed dose rate to the tumors and the normal tissue (TND) was calculated for different tumor sizes and compared with the TND values for (90)Y and (131)I. The normal tissue and tumors were simulated as an ellipsoid and spheres, respectively. The TND values depend on the physical parameters of the radionuclides, the tumor size, and the ratio between the activity concentrations in the tumor and normal tissue (TNC). (153)Sm, (161)Tb, (169)Er, (175)Y...

A highly sensitive and selective spectrofluorimetric method was developed for the determination of ciclopirox olamine in raw material and in dosage forms. The proposed method is based on the formation of a ternary complex with Tb(III) in the presence of ethylenediaminetetraacetic acid. It was found that this complex manifests intense fluorescence at lambda(em) 489 and 545 nm with excitation at 295 nm. Different experimental parameters affecting the fluorescence intensity of the complex were carefully studied and incorporated into the procedure. Under the described conditions, the method is applicable over the concentration range 30-150 and 10-70 ng mL(-1) with minimum detectability of 6.7 and 0.9 ng mL(-1) at lambda(em) 489 and 545 nm, respectively. The mean percentage recovery at lambda(em) 489 and lambda(em) 545 nm ranged between 98.7 and 100.2 for the pure substance, solution, and cream. Relative error of 0.1-0.4% and RDS of up to 0.9% were estimated at lambda(em) 489 and 545 nm....

Intraprotein energy transfer to terbium ions is widely used for probing distances of calcium sites in proteins. In this work we have performed a time-resolved study of the sensitized luminescence in elastase using a pulsed laser excitation at 265 nm. Terbium-sensitized luminescence was found to build-up within about 150 microseconds, which indicates that the protein transfers energy at a rate several orders of magnitude slower than expected for a singlet state donor. From the rise time of the signal and from its variation with the oxygen concentration, it can be deduced that 80% of the transfer originates from the first triplet excited state of one unique aromatic residue. From the comparison of protein fluorescence and sensitized terbium luminescence excitation spectra the sensitizer was identified as a tryptophan, presumably Trp141, which is situated only 0.7-0.9 nm away from the Tb site. The results are at variance with the usual assumption that energy is transferred from the first excited singlet state of aromatic residues according to a long-range dipole-dipole interaction and are more consistent with a short-distance exchange mechanism.

A simple and selective method to determine norfloxacin using an optical flow-through sensor has been developed. The present sensor was prepared by packing anionic ion exchange resin in a glass tube, followed by introducing KMnO4 solution to the glass tube for ...