Distinction of sialyl anomers on ESI- and FAB-MS/MS: stereo-specific fragmentations.
An anomeric pair of the lysoglyceroganglioside 1-O-octadecyl-3-O-(N-acetyl)neuraminyl-sn-glycerol sodium salt was studied to see if sialic anomers were distinguishable by mass spectra. It was evident that, in the electrospray ionization and fast-atom bombardment product-ion spectra: (1) in the positive MS(2) product-ion spectrum, the beta- anomer showed an unexpected aglycone-side sodiated sodium alkoxide ion, which was absent for the alpha-anomer; (2) in both polarities the beta-anomer showed dehydration much more easily than the alpha-anomer; and (3) in the negative MS(2) product-ion spectrum, the beta-anomer also readily showed decarboxylation. Our hypothesis is that, although several easily interconvertible conformations may be allowed, the one having the large aglycone in the equatorial orientation affects the collision-induced dissociation fragmentations.
Ohashi
Yoko
Y
Department of Applied Physics and Chemistry, The University of Electro-Communications, Tokyo, Japan. ohashi@brain.riken.jp
Kubota
Masayuki
M
Hatase
Hiroshi
H
Nakamura
Mitsuhiro
M
Hirano
Takashi
T
Niwa
Haruki
H
Nagai
Yoshitaka
Y
D003653:Decarboxylation; D003681:Dehydration; D005732:Gangliosides / Q000737:chemistry*; D005990:Glycerol / Q000737:chemistry*; D006017:Glycolipids / Q000737:chemistry; D008956:Models, Chemical; D019158:N-Acetylneuraminic Acid / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D013237:Stereoisomerism; D053719:Tandem Mass Spectrometry / Q000379:methods*
C543136:1-O-octadecyl-3-O-(N-acetyl)neuraminylglycerol; D005732:Gangliosides; D006017:Glycolipids; D019158:N-Acetylneuraminic Acid; D005990:Glycerol