Binding constants, boronic acid-diol

Yan J, Springsteen G, Deeter S, Wang B. The relationship between pKa, pH and binding constants in the interaction between boronic acids and diols it is not as simple as it seems. Tetrahedron 2004, 60, 11205-11209. 

Recently, Fabre et al. [31] and Freund et al. [7, 8] used electro-chemically deposited, self-doped, boronic-acid-substituted, conducting polymers for saccharide and fluoride detection. Freund et al. prepared a potentiometric sensor for saccharides using self-doped PABA [7, 8]. The transduction mechanism in that system is reportedly the change in pKa of polyaniline that accompanies complexation, and the resulting change in the electrochemical potential. Sensors produced with this approach exhibit reversible responses with selectivity to various saccharides and 1,2-diols (Figure 3.22) that reflect their binding constants with phenylboronic acid observed in bulk solutions. The sensitivity... 

S. Soundararajan, M. Badawi, C. M. Kohlrust,J. H. Hageman, Boronic acids for affinity chromatography - spectral methods for determinations of ionization and diol-binding constants, Analytical Biochemistry 1989, 178, 125. 

The binding strength of common boronic acids toward ris-diol-contain-ing compounds is relatively weak, with dissociation constants (fif d) between boronic acids and sugars or glycoproteins ranging from 10 to 10 ... 

The second type of applications of boronic acid compounds, described in Sections 13.4 and 13.5, relies on the known strong and reversible complexation between boronic acid and diol (1,2- or l,3-)-containing compounds [3,18]. Importantly, there are three ways to define the binding constants between a boronic acid and a diol (Schemes 13.2 and 13.3), using and Wang and co-workers [3] have ex-... 

A number of publications followed examining the properties and synthesis of boronic acids,with the first quantitative investigation into the interactions between boronic acids and polyols in 1959. In a study to clarify the disputed structure of the phenylboronate anion, Lorand and Edwards added a range of polyols to solutions of phenylboronic acid. The pH of the solutions was adjusted such that there was an equal speciation of phenylboronic acid in its neutral and anionic forms the pH matching the pK. As diol was added the pH of the systems decreased, allowing binding constants to be determined through the technique of pH depression. 

Considering Scheme 7 we define the formation of the diol boronate anion complex as Aitet and the formation of the diol boronic acid complex as ATtrig, where it is observed that ATtet > ATtrig. For instance, the logarithm of these constants for phenylboronic acid binding fructose in 0.5 M NaCl water is log ATtet=3.8 whereas log ATtrig < 1.4. This difference in the value of the binding... 

The value of rate and stability constants are not only dependent on pH there is also a clear dependence on the acidity of the reacting ligand. While the binding of diols by trigonal boronic acids can be considered to be almost negligible, this is not the case when boronic acids complex with more acidic poly-hydroxyl species such as 1,2-diphenols, a-hydroxy carboxylic acids and dicarboxylic acids. ... 

The final point to be considered in boronic acid - saccharide binding is the predisposition of boronic acids to interact with different kinds of diols. The stability constants (K) between various polyols and boronic acids were first quantified by Lorand and Edwards and it is the case that the trends established now appear inherent in all monoboronic acids. ... 

The observed stability constants (Kohs) for the diboronic acid sensors with d-fructose and o-mannose are, at most, twice as strong as with the monoboronic acid sensor 146(pyi.ene)- Each o-fructose and o-mannose molecule will only bind to one boronic acid unit through one diol. This allows complexes to form with... 

Arylboronic acids [63,72,80,85,194] have been most extensively studied as binding sites for derivatised monosaccharides. By using an amino group in the position ortho to the boronic add the rate constant for the esterification with a diol has been increased by a factor of 10 , as mentioned above [79], It has also been shown that the flexibility of the boronic add group is crucial. If the binding interaction is too rigid or too flexible, it is detrimental to the selectivity of the... 

The formation of a diol boronate complex, defined by formally liberates two equivalents of water, but this stoichiometric factor is usually ignored as a constant in dilute aqueous solution. In a formal sense, phenylboronic acid could also bind diols to form a trigonal complex (K jg), and this species would itself act as an acid according to Kj. The acidification of solutions containing phenylboronic acid and diols is always discussed in terms of the trigonal complex being a stronger acid than the parent phenylboronic acid, i.e. K > [17]. Since all the equilibria are coupled this re-... 

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