Lanthanide complexes amino acids

Dissociation constants of 1 1 lanthanide-amino acid complexes. 

Lanthanide Amino Acid Complexes Obtained Under Low-pH Conditions 239... 

Clearly, the coordination ability of an amino acid depends on its specific form, wifh carboxylate and amino groups, and the side chain each potentially coordinating. This feature in turn is critically dependent on the pH condition, ft is thus convenient to present the chemistry of lanthanide-amino acid complexes according to the pH conditions under which the synthesis is carried out. Specifically, the synthetic and structural chemistry of lanthanide complexes with amino... 

LANTHANIDE-AMINO ACID COMPLEXES OBTAINED UNDER LOW-pH CONDITIONS... 

The above discussion suggests that the identity of the lanthanide amino acid complexes, more specifically, the structure of the core motif, is dependent more on the nature of the ligands than on that of the metal ions. With the assistance of small-molecule entities, cluster-type complexes with amino acid ligands with unprecedented structures may be realized. ... 

Amino acid is one of the most important biological ligands. Researches on the coordination of metal-amino acid complexes will help us better understand the complicated behavior of the active site in a metal enzyme. Up to now many Ln-amino acid complexes [50] and 1 1 or 1 2 transition metal-amino acid complexes [51] with the structural motifs of mononuclear entity or chain have been synthesized. Recently, a series of polynuclear lanthanide clusters with amino acid as a ligand were reported (most of them display a Ln404-cubane structural motif) [52]. It is also well known that amino acids are useful ligands for the construction of polynuclear copper clusters [53-56], Several studies on polynuclear transition metal clusters with amino acids as ligands, such as [C03] [57,58], [Co2Pt2] [59], [Zn6] [60], and [Fe ] [61] were also reported. 

These hypersensitive transitions have been studied in a large number of carboxylate and amino-acid complexes of the lanthanides (45—49) and also in biological systems (50, 51) where Ca+2 frequently can be replaced by Ln+8 of... 

While studies on the crystal structures of Ln-amino acid complexes offer a clear picture of how the lanthanide... 

A compound that is able to influence the relaxation times of water protons has to be paramagnetic. In the Periodic System paramagnetic ions are to be found amongst the transition metals and the rare earth metals (lanthanides). However, it was well known, that the free ions of heavy metals are toxic. Lanthanide ions form soluble complexes with ligands such as phospholipids, amino acids and proteins that are present in plasma. The liver and the skeleton are the major sites of accumulation of free metal ions. Uptake in the liver is mediated by the hepa-tocytes [2]. 

The angular and distance information provided by the lanthanide induced shift has found widespread application from the determination of solution structures of Ln chelates [18,19] to gaining structural information on proteins, nucleotides and amino acids [19], More recently anion binding to coordinatively unsaturated lanthanide complexes has been effectively signalled as the observed lanthanide induced shift has been directly correlated to the nature of the donor atom in the axial position [8,20,21], It is the polarisability of the axial donor that ranks the second order crystal field coefficient, B02, and hence determines the magnitude of the observed shift. Values of the mean shift of the four most-shifted axial protons of the 12-Nq ring for [Yb.la]3+ are collated in Table 2. 

Lipophilic lanthanide complexes of fluorinated 3-diketonate ligands were demonstrated to bind unprotected amino acids under neutral conditions. It is not clear whether amino acids are bound as anions or zwitterions. Chiral ligands 63-66 have been prepared and tested for extraction of amino acids from water into dichloromethane [84] (Table 7). NMR and CD spectroscopic... 

Lanthanide complexes with carboxylic acids, amino acids and phosphorus acids [22-24].265... 

Higher complexes of stoichiometries 1 2 and 1 3 have also been reported. It has been suggested that at pH values above 7 amino acid Ln3+ stoichiometry might change from 1 1 to 1 2. It has also been suggested that paramagnetic lanthanides could be used in sequencing peptides from their C-termini [78]. 

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