Lanthanide cations binding

Fig. 1. Representation of the active site region of hen lysozyme, from the X-ray structure (adapted from Ref. 31). The lanthanide cations bind in the region between asp 52 and glu 35.

The estimated distances between lanthanides bound at various cation binding sites on the Ca -ATPase, and FITC, TNP-ATP, Cr-ATP or eosin bound at the nucleotide binding site range between 10 and 47 A [389,390,400,401,407-409,413] (Table II). 

Lanthanides, 1 469-470 14 630-654 25 392. See also Rare-earth entries arc and spark spectra of, 14 633 cation binding of, 24 41 electronic configurations, 1 474t economic aspects of, 14 643-647 health and safety factors related to,... 

It is inappropriate here to discuss details of nmr spectroscopy. However, the full possibilities for structural studies arise from the use of probes that bind to the molecule under study and perturb the nmr spectrum. These probes are generally paramagnetic species, in particular the lanthanide cations. In the nmr spectrum separate signals arise from each nucleus in the molecule, provided that the nucleus possesses a nonzero nuclear spin (e.g., H, 13C, 14N). The extent of the spectral perturbations of a given signal depends on the relative geometries of the paramagnetic species and the nucleus in question. Thus structural parameters can be obtained, in principle, for most atoms (nuclei) in a protein molecule.5... 

In Figure 26-3, an [H+l gradient was used for a cation-exchange separation. The column for this separation has nitrilotriacetic acid groups that bind lanthanide cations in the order... 

Boehme, C., Coupez, B., Wipff, G. 2002. Interaction of M3+lanthanide cations with malonamide ligands and their thia analogues A quantum mechanics study of monoden-tate vs bidentate binding, counterion effects and ligand protonation. J. Phys. Chem. A 106 6487-6498. 

The central hole or binding core in texaphyrins is roughly 20% larger than that of the porphyrins and accomplishes pentadentate binding [247]. In the course of the studies to exploit coordination behavior with lanthanide cations a serious of monoanionic texaphyrine complexes have been synthesized and fully characterized (Eq. 17, Table 20) [248],... 

Dendrimer-type ligand (32) serves as a lanthanide container to exhibit on-off switchable luminescence upon lanthanide complexation in response to external anions [56]. Because of the presence of two classes of coordination sites for the lanthanide cations at the inner and outer spheres, the dendrimer 32 exhibits two different binding modes to afford on-off lanthanide luminescence, in which outer complexation at the tetradentate tripod site offers the on luminescence state upon quinoline excitation whereas, inner complexation at the multidentate core site corresponds to the off luminescence state. Upon complexation of 32 with Yb(CF3 SO3 )3, the quite weak NIR luminescence from the Yb(III) center suggests that the Yb(III) ion is most probably located at the inner coordination sites and apart from the excited quinoline moieties. Nevertheless, addition of SCN anion to the 32-Yb(CF3803)3 system induced remarkable spectral changes around the quinoline absorption band and about ninefold enhancement in luminescence intensity at around 980 nm. As the intense Yb luminescence appeared upon quinoline excitation, the employed SCN anion promoted the tripod-Yb +... 

Electronic energy transfer from an excited state donor to a suitable acceptor is a fundamental process in photochemistry and is of prime importance in artificial photosynthesis. A variety of mechanisms exist by which energy migration and transfer can take placeand such processes have been used to create the so-called antenna effect . In particular, much research has concentrated on designing molecular systems in which an organic host is used to bind a lanthanide cation in such a way that photoexcitation of the host results in intramolecular energy transfer to the bound cation. ... 

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