Encapsulation, affinity ligand

Organo-Silica Monoliths for Affinity Ligand Encapsulation... 

The energetics of peptide-porphyrin interactions and peptide ligand-metal binding have also been observed in another self-assembly system constructed by Huffman et al. (125). Using monomeric helices binding to iron(III) coproporphyrin I, a fourfold symmetric tetracarboxylate porphyrin, these authors demonstrate a correlation between the hydropho-bicity of the peptide and the affinity for heme as well as the reduction potential of the encapsulated ferric ion, as shown in Fig. 12. These data clearly demonstrate that heme macrocycle-peptide hydrophobic interactions are important for both the stability of ferric heme proteins and the resultant electrochemistry. 

The X-ray structure of the L-Sr(Picrate)2 (L = p-tert-butyl-calix[4]arene-tetra(diethylamide)) is reported, as well as MD simulations on the L M2+ complexes in vacuo, in water, and in acetonitrile solutions for alkaline earth cations with a comparison of converging and diverging conformers.130 In the simulated and solid-state structures of the L M2+ complex, the ligand wraps around the complexed cations M2+ (more than it does with alkaline cations), which are completely encapsulated within the polar pseudo-cavity of L, without coordination to its counterion in the crystal or to solvent molecules in solution. In contrast to alkali cation complexes, which display conformational flexibility in solution, computations show that the alkaline earth cation complexes are of the converging type in water and in acetonitrile. Subtle structural changes from Mg2+ to Ba2+ are observed in the gas phase and in solution. Based on FBP calculations, a binding sequence of alkaline earth cations was determined Mg2+ displays the weakest affinity for L, while Ca2+ and Sr2+ are the most stable complexes, which is in agreement with the experiment. 

While the QMOD method is complex, the complexity was driven by the requirements of physical reality. QSAR models of binding affinity must have an inter-dependence between model and molecular pose. There must also be an interdependence between structural variation and predicted bound pose. The models, if they are at all physically sensible, must also encapsulate nonlinear effects such as size exclusion (as in Figure 2.3). Last, ligands with very different underlying scaffolds, as in Figure 2.10, must be modeled in a manner that can recognize their capability to bind the same pocket with similar affinities. 

Alginate/ chitosan Alginate microspheres were prepared by crosslinking with Ca followed by coating with chito.san. Affinity inicrospheres. Blue dexti aii was encapsulated as the ligand to isolate BSA from saline solution and plasma. Achow and Goosan, 1994... 

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