Metal binding ability

In this section, two types of structure-metal binding ability relationships will be described. The first one concerns empirical linear correlations between equilibrium constants of complexation or extraction and some descriptors. In most cases, these correlations are obtained for relatively small datasets (less than 20 molecules) without any validation. We do not intend to analyze them in detail only their general characteristics will be reported. The second type of relationships were obtained in regular QSPR studies involving the selection of pertinent descriptors from their large initial pools, and the stage of the models, validation on external test set(s). 

The examples given here of the use of MM in synthesis are taken from the review by Lipkowitz and Peterson [28]. In attempts to simulate the metal-binding ability of biological acyclic polyethers, the tricyclic 1 (Fig. 3.12) and a tetracyclic analogue were synthesized, using as a guide the indication from MM that these molecules resemble the cyclic polyether 18-crown-6, which binds the potassium ion the acyclic compounds were found to be indeed comparable to the crown ether in metal-binding ability. 

All transfer RNAs (tRNAs) contain a nnmber of modified nncleobases and typically 2 - (9-methylated nncleosides. DNA also contains a more limited nnmber of snch species. Some of these modifications, for example, N-7 methylation of gnanosine, diminish the metal-binding ability of the bases. A few functional groups, such as the exocyclic S in 4-thiouridine and 2-thiocytidine and the exocyclic substituent in 5-carboxymethylaminomethyluridine, enhance the ambivalent nature of the bases. Some of these modifications change the basicity of primary metal-binding sites. 

It is usually assumed that the association-dissociation reactions occur at the membrane interfaces. Selectivity of this facilitated transfer is based on the different affinity of the carrier for the components of the source phase. In artificial liquid membrane systems, crown ethers are widely used as carriers to separate metal ions. Most of the ethers are photoresponsive and their structure and resulting metal-binding ability can be altered under irradiation. 

Metal binding ability chiral ligands or chiral modifiers... 

Whereas extensive information on the metal-binding abilities of mammalian MTs has been compiled, current knowledge of those of non-mammalian species is more limited and rather dispersed. In order to fill this gap, existing data have been summarized in Table 1. A feature commonly found in several MTs is that they contain heterometallic mixtures of two (Zn,Cd Cu,Cd Zn,Cu) or three (Zn,Cd,Cu) metal ions. Still more striking is the great diversity of stoichiometries reported for certain homometallic metal-MT species, as shown in S. cerevisiae, where the copper-to-MT mole ratios range from 4 to 10, and in N. crassa, with a cadmium-to-MT mole ratio of 2 or 3. With this information on the metal-binding properties of MTs, it seems reasonable to conclude that the systematization of these data is hard indeed to achieve. 

Under alkaline conditions, sixteen Pb(II) ions link the secondary hydroxyl side of y-CyD to form a metal-ion-mediated head-to-head dimer [217]. All the secondary hydroxyl groups are deprotonated and coordinated to bind Pb(II) ions forming a hexadecanuclear lead(II) alkoxide. Introduction of ionic substituents on CyDs enhances their metal-binding ability. Two amino groups introduced on the primary hydroxyl side of jS-CyD can chelate a platinum ion [64]. Imidazole-appended yS-CyD forms a ternary complex with a Cu(II) ion and L-tryptophanate [61]. The 6-amino and imidazolyl groups of the host molecule and the carboxyl and amino groups of L-tryptophanate are coordinated to the Cu(II) ion. 

Given psyllium s strong metal binding ability and its possible role in uniform dispersion of the ions and their subsequent release under suitable conditions, it could be particularly beneficial to systems including silver and copper ions which are popular with antimicrobial functionalities. Singh et al (37) have studied psyllium potentials in... 

Horiuchi S, Tachibana Y, Yamashita M, Yamamoto K, Masai K, Takase K, Matsutani T, Kawamata S, Kurashige Y, Yanai T, Murahashi T (2015) Multinuclear metal-binding ability of a carotene. Nat Commun 6. doi 10.1038/ncomms7742... 

Table 7.5 Metal-binding abilities of some of the newer buffers ...

The metal binding ability of bleomycin was apparent from its isolation as the copper chelate, and derivatives of interest besides Cu and Fe (see... 

Schone 2 Two tautomeric forms—iminothiol (top) and thioamide (bottom) of rubeanic acid (5) and the structure of molecule 6. Notice that the thiol and phenol groups are mitigated in their metal-binding ability by the adjacent electron-withdrawing imine and oxime units, respectively... 

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