A benzoboroxole-functionalized monolithic column was synthesized, which exhibited the best specificity and affinity towards cis-diol containing biomolecules as compared with the boronate affinity monolithic columns reported as well as significant secondary separation capability under acidic conditions.

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A new Wulff-type boronate was designed and synthesized. Upon immobilization on a polymeric monolith and acidified as boronic acid, the ligand exhibited specific boronate affinity to cis-diol compounds at medium acidic pH condition.

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The affinity of boronic acids to cis-diol-containing biomolecules has found wide applications in many fields, such as sensing, separation, drug delivery, and functional materials. A sound understanding of the binding interactions will greatly facilitate exquisite applications of this chemistry. Although a few analytical tools have been available for the characterization of the interactions, these techniques are associated with some apparent drawbacks, so they are only applicable to a limited range of boronic acids and cis-diol-containing biomolecules. Therefore, a widely applicable method is still greatly needed. In this work, an affinity capillary electrophoresis (ACE) method was established and validated to probe the interactions between boronic acids and cis-diol-containing biomolecules. The method was proven to be applicable to almost all types of cis-diol-containing biomolecules and boronic acids. Based on this method, a quantitative, comparative study on the interactions between 14 boronic acids that have important potentials for application with 5 typical monosaccharides of biological importance was carried out. The findings provided new insights into boronate affinity interactions, particularly the relationship between the binding strength with the molecular structures of the binding species. Besides, effects of pH and temperature on the binding strength were also investigated. This method exhibited several significant advantages, including (1) possibility of simultaneous study of multiple interactions, (2) low requirement on the purity of the binding species, (3) wide applicability, and (4) high accuracy and precision.

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A new hydrophilic boronate affinity monolithic capillary was synthesized for the selective capture of cis-diol biomolecules including glycoproteins and nucleosides, using (3-acrylamidophenyl)boronic acid (APBA) and N,N-methylenebisacrylamide (MBAA) as the functional monomer and cross-linker, respectively. A comparison with other compositionally similar monolithic capillaries was carried out in terms of reversed-phase retention, selectivity, binding capacity and binding pH. The poly(APBA-co-MBAA) monolithic capillary exhibited notably different properties. As both the functional monomer and the cross-linker are hydrophilic, the monolith capillary showed suppressed reversed-phase retention and as a result excellent selectivity toward both nucleosides and glycoproteins was observed. It exhibited the highest binding capacity as compared with other compositionally similar monolithic capillaries. Besides, because of the lower pK a value of APBA, the monolithic capillary was able to selectively capture nucleosides at near-physiological pH.