Solid-phase-bound ligand

To examine the chemical behavior of these new ligands 48-50 in coordination chemistry, tricarbonyl complexes with manganese and rhenium were synthesized from [MnBr(CO)s] and [ReBrCCOls] as described earlier for the other heteroscorpionate ligands (Scheme 28). The purpose of these tricarbonyl complexes was to verify tripodal binding of the solid-bound ligand. The protected OH linker in 50 acts as model for the solid phase bound ligand. 

Jackson et al. furthermore prepared the solid-phase-bound ligand libraries 23 shown in Scheme 9 (27). The ligands consist of a solid-phase-bound dipeptide which is capped by a salicylic aldehyde. The screening of a number of... 

Scheme 9. Solid-phase-bound ligands for the titanium-catalyzed asymmetric sulfoxidation of thioethers.

Streptavidin-single-stranded DNA covalent conjugates were described as the building blocks for assembling nanostructured scaffolds [31], The amount and type of biotinylated ligands were used to modulate the affinity of duplex formation between solid-phase-bound nucleic acid templates and DNA-streptavidin conjugates. This system has been proposed for the design of fine-tuned sequence detection systems. 

Recently, also direct recognition of active ligands attached to bead surfaces has been achieved with immunodetection [14]. This provides a rapid and automated screening tool which is compatible with solid-phase bound compounds originating from solid-phase chemistry in combinatorial chemistry. However, this approach has so far only been published for a model system. 

Lamaty and coworkers used PEG-bound Ru catalysts for metathesis reactions [71]. In contrast to solid-phase-bound catalysts, the soluble polymeric support allowed for analysis which provided information on the recycling capacities of the catalyst while the activity remained high, the return of the metal on the supported ligand was not total. 

In the solid phase type of separation the antibody or binding protein is bound to an inert material such as Sephadex or glass beads yet is still free to react with the ligand. 

Nonspecific protein binding to the solid phase complicates the method and is a selective pressure driving its evolution. The adaptive response has been the development of intrinsically comparative methods in which specific binding to an immobilized ligand is blocked in one out of two otherwise identical samples. When the respective protein components of the samples are compared, specifically bound proteins are present in one but severely depleted in the other. To allow relative quantitation, the two samples can be made isotopically distinct by a chemical or metabolic process and then mixed for an analytical step that avoids intersample variability [15]. 

There is one more report on the synthesis of a library of phosphorus ligands on solid phase. Waldmann et al. prepared a library of phosphoramidites on beads (Fig. 36.5), but these were only applied in enantioselective C-C-bond formation. In fact, as two ligands need to be bound to the catalyst, the use of an immobilized monodentate ligands should most likely be avoided unless the proximity between the ligands is sufficiently close. In addition, crosslinking by the metal may have a negative impact on the permeability of the polymer for the substrate. 

Figure 15.4 Binding of bombykol to BmPBP at pH 7 as demonstrated by the cold-binding assay. After removal of the unbound ligand, bound bombykol was extracted from the ligated protein with a solid phase microextraction syringe (SPME, 65 pm polydimethylsiloxane divinylbenzene coating). Under the same conditions, but at low pH (5), the amount of ligand extracted is not significantly different from the amount extracted from a buffer solution (control).

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