Single‐Molecule Determination of the Isomers of d‐Glucose and d‐Fructose that Bind to Boronic Acids

Abstract

Monosaccharides, such as d-glucose and d-fructose, exist in aqueous solution as an equilibrium mixture of cyclic isomers and can be detected with boronic acids by the reversible formation of boronate esters. The engineering of accurate, discriminating and continuous monitoring devices relies on knowledge of which cyclic isomer of a sugar binds to a boronic acid receptor. Herein, by monitoring fluctuations in ionic current, we show that an engineered α-hemolysin (αHL) nanopore modified with a boronic acid reacts reversibly with d-glucose as the pyranose isomer (α-d-glucopyranose) and d-fructose as either the furanose (β-d-fructofuranose) or the pyranose (β-d-fructopyranose). Both of these binding modes contradict current binding models. With this knowledge, we distinguished the individual sugars in a mixture of d-maltose, d-glucose, and d-fructose.

Boronic acids as building blocks for the construction of therapeutically useful bioconjugates

“…Despite being very important, these uses will not be covered here and the reader is directed to excellent existing reviews on this topic. 86,91,92 Over the years, BEs have assumed a significant role in bioconjugation by enabling the construction of hybrid materials that exhibit a dynamic nature. The formation and transesterification of BEs under aqueous conditions are highly dependent on the diol-BA affinity.…”

Recent development of boronic acid-based fluorescent sensors

“…165 According to the uctuation of the ion current generated by the binding of the boronic acid-modied engineering protein nanopore to different sugars, this method can determine the binding mode, thereby realizing the differentiation of different carbohydrates. In the disaccharide (D-maltose) and monosaccharide (D-glucose) mixture components, it is easy to discriminate by visually checking the current recording.…”

Nanopore Analysis of the 5-Guanidinohydantoin to Iminoallantoin Isomerization in Duplex DNA

“…15–18 The α-HL protein nanopore has been harnessed as a nanoreactor to follow the reaction evolution for the click reaction, 19 1,4-Michael additions, 20 and an enzyme-catalyzed reaction on DNA. 15,21 The sensitivity of the α-HL to monitor molecular structure allowed determination of epimers of carbohydrates, 22 amino acid enantiomers, 23 isomers of heteropolytungstates, 24 and diastereomers in duplex DNA. 25 Additionally, the latch zone of the α-HL protein was identified by the Burrows/White laboratories to possess high sensitivity for monitoring base pairs in duplex DNA.…”