Accepted: Glish Andy Baker Uni NC Chapel Hill

Introduction

The complex aspects of carbohydrate stereochemistry and anomericity have dramatic influences on the chemistry and biochemistry of living systems. Analytical chemistry techniques including NMR and mass spectrometry have been used to probe simple and more complex sugars. High resolution IMS using a variable pathlength mobility separator and multiple stages of IMS (further separation of mobility-selected sub-populations) can be used to probe the complex mixture of isomeric carbohydrates.

Methods

Ten micromolar mono (arabinose, xylose, A and B methyl glucoside, glucose, galactose, and mannose) or disaccharide (sucrose, maltose, isomaltose, cellobiose, trehalose, lactose, and lactulose) in 100 micromolar lithium acetate were analyzed using ESI+ on on a cyclic ion mobility enabled quadrupole time-of-flight (Q-cIM-oaToF) mass spectrometer with a one meter cyclic mobility cell using nitrogen as the buffer gas. IMS path length and resulting IMS resolution were varied by increasing residence time in the mobility separator. Tandem IMS experiments were performed on mobility-resolved species by isolating selected ion populations in an external ion trap before reinjecting into the mobility separator. By changing the voltage offset between the ion trap and mobility separator during ion reinjection, fragmentation or structural changes were induced.

Preliminary Data

Lithium cationized monosaccharides were analyzed using a novel cyclic ion mobility separator (cIM). By increasing the delay time between ion injection and ejection from the cIM, ion pathlength and corresponding IMS resolution are increased. Using a 5 meter (five passes) effective path length, Glucose, fructose, xylose, and arabinose were separated into two distinct populations. Using an 11 meter pathlength, galactose was resolved into at least four species. Post mobility fragmentation of the populations showed different ratios of fragment ion formation, suggesting different structures. For galactose, loss of C2H4O3 is not observed for the last isomer.

The glucose and galactose arrival time distributions (ATD) were studied using a tandem IMS experiment. Mobility selected regions of the ATD corresponding to the most intense resolvable features were isolated and reinjected into the cIM with and without activation. While there was some fragmentation observed for the first ATD peak in glucose (dehydration), there was no interconversion between the two populations, suggesting that the structures are stable in the gas phase. There was no fragmentation observed for either of the major ATD peaks in galactose.

Several of the lithium cationized disaccharides (melibiose, lactulose, and isomaltose) were resolved into two species using 15 meter effective path length while trehalose, lactose, and cellobiose were homogeneous peaks after 30 passes (30 m effective path length). There were few qualitative or quantitative differences in the fragmentation patterns for the resolvable species.

Novel Aspect

Use of high resolution IMS and tandem IMS experiments to probe structure and isomerization of lithium and sodium cationized carbohydrates.

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A post-doc is presenting author on this abstract? No 

A graduate student is presenting author on this abstract? No
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Poster:

Carbohydrates

Submitting Author:

Andrew Baker
Waters, Inc.
Pleasanton, CA
andy_baker@waters.com