Influence of molecular configuration and conformation on the electromigration of oligosaccharides in narrow bore capillaries

Abstract

Capillary electrophoresis enables fast, high efficiency separations of oligosaccharides, wherein positional and/or linkage isomers, bearing the same charge-to-mass ratio, can readily be separated based on hydrodynamic radius differences. Fundamental electrophoretic mobility theory was used to investigate the correlation between changes in hydrodynamic volume equivalent radius and corresponding electrophoretic characteristics of oligosaccharides with different molecular properties. Fluorescently derivatized isomeric malto-, cello-, and isomaltooligosaccharide ladders, differing only in their linkage type of α1→4, β1→4, and α1→6, respectively, as well as a sterically larger N-acetylchitooligosaccharide ladder were used as model compounds. Mere differences in glycosidic linkage type or anomericity of isomeric oligo-glucoses had a decisive impact on their electromigration behavior, thus reflecting discrepancies in hydrodynamic radii and associated molecular conformations. The impact of hydrogen bridges, and associated availability of hydroxyl groups, on the molecular conformations, was investigated by hydrophilic interaction liquid chromatography. The experimentally observed electrophoretic and chromatographic differences between isomeric oligo-glucoses strongly suggested that special attention must be given when homooligosaccharide ladders are employed for normalization and comparability purposes, for example, in glucose unit calculation based structural elucidation.

Characterization of hydrothermally isolated xylan from beech wood by capillary electrophoresis with laser-induced fluorescence and mass spectrometry detection

“…Close inspection of the graph representing the a-(1 ? 4)-linked gluco-oligosaccharides revealed linear fittings in 2 separated sections of DP below 9 and above 9, which has also been observed before with a slope of -0.62 for DP 1-9 and -0.68 for DP 9-24 indicating a relaxed helical structure of the oligosaccharides with some minor change in the overall geometry around DP 9 (Mittermayr and Guttman 2012). In the present study, a slope of -0.68 (r 2 = 0.9997) was found for the range from 1 to 9 units of the glucose ladder while a slope of -0.75 (r 2 = 0.9998) resulted for the saccharides with a DP above 9.…”

“…In the present study, a slope of -0.68 (r 2 = 0.9997) was found for the range from 1 to 9 units of the glucose ladder while a slope of -0.75 (r 2 = 0.9998) resulted for the saccharides with a DP above 9. The latter value is higher than the previously reported data (Mittermayr and Guttman 2012) but still close to a value of 2/3 so that a helical structure can also be assumed for the gluco-oligosaccharides in the present study. The b-(1 ?…”

“…For peak identification, the commercially available standards xylose (X1), xylotriose (X3) and xylohexaose (X6) were analyzed separately as well as spiked into a HTX-n sample (data not shown). The tentative assignment of the unknown major xylooligosaccharide peaks was based on the regular increase of the electrophoretic mobility of the individual oligosaccharides within a homo-oligosaccharide ladder (Mittermayr and Guttman 2012).…”

“…An exponent of 2/3 suggests a random coil structure of the analytes while a linear conformation is suggested for an exponent of 1 (Mittermayr and Guttman 2012). A glucose ladder composed of a-(1 ?…”

Comparison of separation techniques for the elucidation of IgG N-glycans pooled from healthy mammalian species

“…29 In either separation mechanism, each sugar chain oligomer has a distinct retention/ migration time. By correlation of the retention/migration time and length of the sugar oligomer a calibration is generated to assign GU (glucose units), AU (arabinose units) and GU CE (glucose units for capillary electrophoresis) values to unknown oligosaccharides.…”