Affinity enhancement

Fig. 3.5 Example of affinity enhancement through jS-alanine (j8) substitution between two imidazole residues. The Im-j6-lm unit increases affinity by 100-fold over the Im-Py-lm parent molecule...

To evaluate the influence of structural parameters governed by the cyclophosphazene core concerning the valency and the spatial orientation of epitopes, as well as the nature of linkers directly related to the ligation technique used for the mannoside incorporation, the authors performed preliminary kinetic turbidimetric assays with Con A. Insoluble cross-linked complexes formed rapidly for all compounds, without marked difference for the hexavalent analogues. On the other hand, the incorporation of additional mannosyl units led merely to statistical binding-affinity enhancements, notably for the less-dense decamer 194, which presents favorable extended intersugar distances. 

Lee RT, Lee YC. Affinity enhancement by multivalent lectin-carbohydrate interaction. Glycoconjug J 2000 17 543-551. 

Kipryanov, S. M, Little, M, Kropshofer, H., Breitling, F., Gotter, S., and Diibel, S. (1996) Affinity enhancement of a recombinant antibody, formation of complexes with multiple valency by a single-chain Fv fragment-core Streptavidin fusion. Protein Eng 9,203—211... 

Owing to the weakness of carbohydrate receptor-protein interactions, in order to attain biological meaningful affinities for the receptor, carbohydrates very often need to be clustered and expressed in multiple copies. For this purpose glycodendrimers, which are multivalent glycoconjugates with well-defined chemical structures, have received recent attention for their considerable potential as tools for studying cell-surface protein-carbohydrate interactions, because of the affinity enhancement obtained by multivalency. 

Low Molecular Weight Multivalent Ligands Show Some Affinity Enhancement for the Selectins... 

Cheong, H. S., Chang, J. S., Park, J. M., and Byun, S. M. (1990) Affinity enhancement of bispecific antibody against two different epitopes in the same antigen. Biochem. Biophys. Res. Commun. 173, 795-800. 

It has been proposed that the Ns position of DHF is protonated by a Glu of DHFR (59) and, in cationic form, binds to DHFR Asp through an electrostatic bond (Fig. 42.30). Ns is the strongest base in the DHF structure, in part because of attenuating the impact of the C4 carbonyl on electron density around Ni. Additional affinity-enhancing interactions between enzyme and substrate also have been identified (60,61), and once bound, the substrate 5,6-double bond is positioned close to the NADPH cofactor so that the transfer of hydride can proceed. 

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