Cationic labeling of oligosaccharides for electrophoretic preconcentration and separation with contactless conductivity detection

A New Strategy Coupling Ion-Mobility-Selective CID and Cryogenic IR Spectroscopy to Identify Glycan Anomers

Determining the primary structure of glycans remains challenging due to their isomeric complexity. While high-resolution ion mobility spectrometry (IMS) has recently allowed distinguishing between many glycan isomers, the arrival-time distributions (ATDs) frequently exhibit multiple peaks, which can arise from positional isomers, reducing-end anomers, or different conformations. Here, we present the combination of ultrahigh-resolution ion mobility, collision-induced dissociation (CID), and cryogenic infrared (IR) spectroscopy as a systematic method to identify reducing-end anomers of glycans. Previous studies have suggested that high-resolution ion mobility of sodiated glycans is able to separate the two reducing-end anomers. In this case, Y-fragments generated from mobility-separated precursor species should also contain a single anomer at their reducing end. We confirm that this is the case by comparing the IR spectra of selected Y-fragments to those of anomerically pure mono- and disaccharides, allowing the assignment of the mobility-separated precursor and its IR spectrum to a single reducing-end anomer. The anomerically pure precursor glycans can henceforth be rapidly identified on the basis of their IR spectrum alone, allowing them to be distinguished from other isomeric forms.

Microfabricated Liquid Junction Capillary Electrophoresis-Mass Spectrometry Interface

Coupling of capillary electrophoresis (CE) with mass spectrometry (MS) represents a powerful combination for performing rapid, efficient, and sensitive analysis of a variety of compounds. Here we describe a construction, operation, and application of a microfabricated liquid junction CE-MS interface. The interface is designed as a microfabricated unit with an integrated liquid junction and electrospray tip made from polyimide, which is positioned in a plastic connection block securing the separation CE capillary and attachable to the CE instrument. The application was demonstrated by CE-MS analysis of dextran oligomers labeled by (2-aminoethyl)trimethylammonium (AETMA) salt.

One-pot production of maltoheptaose (DP7) from starch by sequential addition of cyclodextrin glucotransferase and cyclomaltodextrinase

Maltodextrins (dextrins) are glucose chains normally produced by starch hydrolysis. Maltodextrins are characterized by their degree of polymerization (DP), which indicates the average number of glucose units per chain. Maltoheptaose (DP7), also known as amyloheptaose, is one of the maltodextrin mixtures widely used in foods, cosmetics, and pharmaceutical industries. Recently, the enzymatic synthesis of DP7 has attracted considerable attention, owing to its considerable advantages over chemical methods. In this work, we have designed a one-pot cascade reaction bio-synthesis starting from soluble starch to produce a specific degree of polymerization (DP7). The reaction system was catalyzed by cyclodextrin glucotransferase (GaCGT) from Gracilibacillus alcaliphilus SK51.001CGTase (transglycosylation/cyclization reaction) and cyclomaltodextrinase (BsCD) from Bacillus sphaericus E-244CDase (ring-opening reaction). The one-pot cascade reaction exhibited an optimum temperature of 30 °C and pH 7.0, and the addition of Ca²⁺ enhanced the maltoheptaose production. The optimum enzyme units for the one-pot cascade reaction were 80 U/g of GaCGT and 1 U/g of BsCD. However, the sequential addition of the enzymes exhibited a 5-fold higher conversion rate over simultaneous addition. The one-pot cascade reaction converted 30 g/L of soluble starch to 5.4 g/L of maltoheptaose in 1 h reaction time with a conversion rate of 16 %.

Microfabricated liquid junction hybrid capillary electrophoresis-mass spectrometry interface for fully automated operation

One of the challenging instrumental aspects in coupling an automated CE instrument with ESI mass spectrometry (CE-MS) is finding the balance between the stability, reproducibility and sensitivity of the analysis and compatibility with the standard CE instrumentation. Here, we present a development of a new liquid junction based electrospray interface for automated CE-MS, with a focus on the technical design followed by computer modeling of transport conditions as well as characterization of basic performance of the interface. This hybrid arrangement designed as a microfabricated unit attachable to the automated CE instrument allows using of a wide range of separation capillaries with respect to their diameter, length or internal coating (e.g., for suppressed electroosmotic flow). Different compositions of the ESI liquid and background electrolyte solutions can be used if needed. The microfabricated part, prepared by laser machining from polyimide, includes a self-aligning liquid junction, a short transport channel, and a pointed sprayer for the electrospray ionization. This microfabricated part is positioned in a plastic connection block securing the separation capillary and flushing ports. Transport conditions were modelled using computer simulation and the real life performance of the interface was compared to that of a commercial sheath liquid interface. The basic performance of the interface was demonstrated by separations of peptides, proteins, and oligosaccharides.

Fluorescence detector for capillary separations fabricated by 3D printing

A simple inexpensive light-emitting diode (LED)-based fluorescence detector for detection in capillary separations is described. The modular design includes a separate high power LED source, detector head, designed in the epifluorescence arrangement, and capillary detection cells. The detector head and detection cells were printed using a 3D printer and assembled with commercially available optical components. Optical fibers were used for connecting the detector head to the LED excitation source and the photodetector module. Microscope objective or high numerical aperture optical fiber were used for collection of the fluorescence emission from the fused silica separation capillary. As an example, mixture of oligosaccharides labeled by 8-aminopyrene-1,3,6-trisulfonate (APTS) was separated by capillary zone electrophoresis and detected by the described detector. The performance of the detector was compared with both a semiconductor photodiode and photomultiplier as light sensing elements. The main advantages of the 3D printed parts, compared to the more expensive alternatives from the optic component suppliers, include not only cost reduction, but also easy customization of the spatial arrangement, modularity, miniaturization, and sharing of information between laboratories for easy replication or further modifications of the detector. All information and files necessary for printing the presented detector are enclosed in the Supporting Information.