Monovalent peptide

By carefully adjusting the distances between two sialoside residues in a number of divalent clusters. Click and Knowles [105] have obtained dimer 104 having the two sialic acid 5.7 nm apart. Compound 104 was 100-fold more potent than methyl a-sialoside (Neu5Aca2Me) in influenza virus inhibitions and 500-fold more potent in the case of polyomia virus. Alternatively, sialyl-a-(2,6)-/3-LacNAc dimers (105) branched at different positions of synthetic peptides, including compact glycine-rich and helical proline-rich peptides, afforded clusters which were only 8- and 4-fold more potent, respectively, than the corresponding monovalent trisaccharide [106]. 

Various geometrical shapes have been observed upon addition of monovalent alkaline cations to the peptides.135,150 SEM and AFM studies revealed interwoven nanofibers... 

Polycations are strongly retained by the bare silica capillary wall, since they can ion-pair at multiple sites on the anionic wall. Since all electrostatic bonds must be broken to free the solute, this problem becomes increasingly severe as the number of positive charges increases. Polycations may include small molecules such as tetrazoles and even small peptides. Either permanently coated or charged-reversed capillaries are usually required to separate polyvalent cations. Monovalent cations show some wall effects, but these do not preclude the bare silica capillary from being used. Polyanions and monovalent anions can usually be separated on bare silica. 

Much like the search for protein-binding compounds requires consideration of tertiary structure in addition to peptide sequence, thinking about selective nucleic acid binding solely in the context of primary sequence is often an oversimplification. In the context of DNA recognition, a particularly important example of this is the case of G-quadruplexes. As their name implies, these structures consist of stacked tetrads of guanosine bases, typically ordered around a monovalent cation. One representative structure, a quadruplex derived from human telomeric DNA, is shown in Fig. 5 many variants of this motif formed by either parallel or antiparallel DNA strands have been observed. 

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