Analysis of Saccharides by the Addition of Amino Acids

Abstract

Abstract. In this work, we present the detection sensitivity improvement of electrospray ionization (ESI) mass spectrometry of neutral saccharides in a positive ion mode by the addition of various amino acids. Saccharides of a broad molecular weight range were chosen as the model compounds in the present study. Saccharides provide strong noncovalent interactions with amino acids, and the complex formation enhances the signal intensity and simplifies the mass spectra of saccharides. Polysaccharides provide a polymer-like ESI spectrum with a basic subunit difference between multiply charged chains. The protonated spectra of saccharides are not well identified because of different charge state distributions produced by the same molecules. Depending on the solvent used and other ions or molecules present in the solution, noncovalent interactions with saccharides may occur. These interactions are affected by the addition of amino acids. Amino acids with polar side groups show a strong tendency to interact with saccharides. In particular, serine shows a high tendency to interact with saccharides and significantly improves the detection sensitivity of saccharide compounds.

Interplay of H‐Bonds with Aromatics in Isolated Complexes Identifies Isomeric Carbohydrates

“…), although not all of them are essential in nature.I nc ontrast to amino acids and nucleotides,t hese isomeric units can interconnect through different OH groups, forming regioisomers,but also at multiple points,assembling into linear and branched structural isomers.N atural modifications (for example, N-acetylation) of different units further multiply the number of possible isoforms.Human milk alone, for instance,c ontains at least 200 different oligosaccharides, many of which are essential not only for supplying energy to newborns,but also for their antibacterial defense. Both problems can potentially be solved by sensing noncovalent complexes of carbohydrates with protonated aromatic molecules, [13] relying on the fact that the UV absorption of many aromatics,i ncluding aromatic amino acids,i s sensitive to intra-and intermolecular hydrogen bonds. [9] Them ethods rely on rates of hindered travel of molecules and ions,w hich are not fundamental values and are known to be sensitive to the experimental conditions and instrumentation.…”

“…[9] Them ethods rely on rates of hindered travel of molecules and ions,w hich are not fundamental values and are known to be sensitive to the experimental conditions and instrumentation. Both problems can potentially be solved by sensing noncovalent complexes of carbohydrates with protonated aromatic molecules, [13] relying on the fact that the UV absorption of many aromatics,i ncluding aromatic amino acids,i s sensitive to intra-and intermolecular hydrogen bonds. Vibrational spectroscopy in the gas phase (for example,infrared multiple photon dissociation [10] or IR-induced fragmentation of tagged saccharides [11] )w as able to distinguish, though without quantification, many stereoisomers of small oligosaccharides.…”

“…Additionally,c arbohydrates are not prone to protonation. Both problems can potentially be solved by sensing noncovalent complexes of carbohydrates with protonated aromatic molecules, [13] relying on the fact that the UV absorption of many aromatics,i ncluding aromatic amino acids,i s sensitive to intra-and intermolecular hydrogen bonds. [14] But how sensitive are the intermolecular non-covalent bonds in communicating structural details between molecules?Will, for instance,aflip of asingle OH group in alarge isomeric oligosaccharide noticeably change the UV spectrum of aw eakly bound aromatic?H erein, we demonstrate how an etwork of non-covalent bonds between an aromatic host [*] E. Saparbaev,D r. V. Kopysov,D r. A. Y. Pereverzev,Dr.…”

“…Additionally,c arbohydrates are not prone to protonation. Both problems can potentially be solved by sensing noncovalent complexes of carbohydrates with protonated aromatic molecules, [13] relying on the fact that the UV absorption of many aromatics,i ncluding aromatic amino acids,i s sensitive to intra-and intermolecular hydrogen bonds. [14] But how sensitive are the intermolecular non-covalent bonds in communicating structural details between molecules?Will, for instance,aflip of asingle OH group in alarge isomeric oligosaccharide noticeably change the UV spectrum of aw eakly bound aromatic?H erein, we demonstrate how an etwork of non-covalent bonds between an aromatic host ion and ac arbohydrate guest molecule enables specific bilateral responses of the complex to structural differences in isomeric guests.T he responses,detected by acombination of gas-phase UV spectroscopy and mass spectrometry,reveal key functions of the non-covalent bonds in communicating structural differences of the guests.Weexplore the use of such networks for the identification and quantification of all types of isomers of carbohydrates non-covalently bound to protonated aromatic host molecules in solution.…”