Soluble macroligands

This approach was used to estimate the constants of conplex formation for CXi(2+) and Ni(2+), the conplexes incorporating with polyethylene (PE)-grafted - poly (acrylic) acid (12, 13). For cross-linked polymers K is one-two orders of magnitude hi er than that for soluble macroligands. However, the rate of metal complex formation is markedly lower than that of linear polymers and is controlled by the... 

The recovery was 50-75%, with respect to the amount of receptor present in the aggregate-free preparation (depending on the initial quality of the calf uterus tissue), and the purity was estimated to about 80%. These results were quite competitive with those afforded by traditional affinity chromatography [22,23], if not better, and were obtained in a short time without previous experience in the field of estrogen receptor purification. The quantity of material that could be treated by this technique was only limited by the size of the gel filtration columns. On the other hand, the water-soluble macroligand could be recovered in the void volume of the column, at the second filtration step, and recycled for further purification experiments, after removal of the non-specifically bound contaminants. 

The binding of functionalized chiral ligands to water-soluble polymers has also been shown a (diphenylphosphino)pyrrolidine derivative reacts with poly(acrylic acid) to form a macroligand that is useful in biphasic reduction (35). 

Polymer carriers with a grafted functional surface layer (i.e., the soluble functional covering on an insoluble substrate) occupies an intermediate position between soluble and cross-linked macroligands. Such polyligands present interest due to the fact that the functional groups localized on the surface facilitate the... 

Recently, it has been shown that coupling the chiral ligand PPM with a water-soluble poly(acrylic acid) gave a macroligand 9, the rhodium complex of which allowed the reduction of amino acid precursors in water or water/ethyl acetate as the solvents with enantioselectivity up to 56 and 74%, respectively [41]. 

Carboxylate groups were used in many cases to achieve water-solubilization of simple achiral phosphines. With the synthesis of the water-soluble polymer shown in Eq. (2) this methodology was extended into the field of chiral ligands [28a]. Acylation of the diphosphine (2S,4S)-4-diphenylphosphino-2-diphenylphosphinome-thylpyrrolidone (PPM) with poly(acrylic acid) (PPA) yields the hydrophilic macroligand PAA-PMM [28a,b] and PAA-pyrphos [28c]. 

The binding of the chiral ligand PPM to a water-soluble polymer such as polyacrylic acid gave a macroligand 27 [29], which was used in the reduction of a-acet-amidocinnamic acid (13 c) enantioselectivities up to 56% and 74% were obtained using water and EtOAc/HzO (1 1) as the solvents, respectively. 

In cases of macroligands of appropriate structure, exemplified by cyclodextrins, molecular recognition may increase the aqueous solubility of the substrate and may contribute to the rate and selectivity of its catalytic transformation. 

The most common way of preparing affinity-electrophoresis immobilized ligands is to synthesize a water-soluble macromolecular derivative of the ligand, called a macroligand. This is currently achieved by copolymerization of an acryloyl derivative of the ligand with acrylamide or a related monomer. 

Monomers of metal complexes/chelates suitable for polymerizations, and also polycondensations or polyaddition reactions, can be employed successfully for the preparation of metal containing polymers. In most cases polymerizations are carried out in the presence of a comonomer to obtain polymers with sufficient solubility. For polymerizations either a vinyl group containing ligand is polymerized followed by introduction of a metal ion in the macroligand, or the vinyl group containing metal complex/chelate is directly converted into the MMC. In some cases when chain transfer due to a transition... 

Another important feature of complex formation with macroligands is the presence of different types decompositions that appear both within and between the polymer chains. As a result, several types of metal centers form simultaneously. Transformations between complexes sometimes do not occur and, therefore, result in the coexistence of fully coordinated macroligands or differently coordinated complexes in addition to the free macroligands, even at a low level of functional group conversion. Complex formation in solution proceeds rapidly and is accompanied by the loss of polymer ligand solubility that results in precipitation of different types of complexes, particularly at high values of 0. Both intramolecular and intermolecular complexes with a similar or different metal coordination number (CM) can form. Moreover, the number of defects in the coordination centers increases with rigidity of a molecular skeleton. 

Freitag R. Reversibly water-soluble affinity macroligands for bioseparation. Curr Trends Polym Sci 1998 3 63-79. 

The new concept consists of the preparation of water-soluble biospecific polymers, the macroligands, so that a reversible biospecific water-soluble complex is formed with the desired target molecule. Provided that the parent polymer possesses any distinctive feature allowing an easy discrimination of this complex from the rest of contaminants - high molecular weight, high density of charges, precipitability, etc - all kinds of new, versatile techniques then become available to fractionate the mixture. 

A water-soluble polymer, made biospecific after covalent coupling to an adequate ligand - resulting all together in a so-called macroligand - forms a water-soluble specific and reversible complex with the target molecule, when dissolved in the starting mixture. 

Poly(ethylene glycol) is the most widely used polymer to prepare macroligands for affinity partition. This is probably partly due to its solubility both in... 

The last distinctive feature that has been exploited to discriminate between contaminants and the complex formed between a target molecule and a water-soluble biospecific macroligand, is the reversible soluble-insoluble character of the parent polymer. 

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