title: Preparation and structural characterization of large heparin-derived oligosaccharides.
abstract: Porcine mucosal heparin was partially depolymerized with heparin lyase I and then fractionated into low-molecular-weight (< 5000) and high-molecular-weight (> 5000) oligosaccharides by pressure filtration. The high-molecular-weight oligosaccharide mixture (approximately 50 wt% of the starting heparin) also contained intact heparin. This intact polymer complicates oligosaccharide purification. Thus, the low-molecular-weight fraction was used to prepare homogeneous oligosaccharides for structural characterization. The low-molecular-weight oligosaccharide mixture was first fractionated by low-pressure gel permeation chromatography into size-uniform mixtures of disaccharides, tetrasaccharides, hexasaccharides, octasaccharides, decasaccharides, dodecasaccharides, tetradecasaccharides and higher oligosaccharides. Each size-fractionated mixture was then purified on the basis of charge by repetitive semi-preparative strong-anion-exchange high-performance liquid chromatography. This approach has led to the isolation of 14 homogeneous oligosaccharides from disaccharide to tetradecasaccharide. The purity of these heparin-derived oligosaccharides was determined by gradient polyacrylamide gel electrophoresis, analytical strong-anion-exchange high-performance liquid chromatography, capillary electrophoresis and one-dimensional nuclear resonance spectroscopy. The structure of these oligosaccharides was established using 600 MHz two-dimensional nuclear resonance spectroscopy. The spectral methods used included homonuclear correlation spectroscopy, nuclear Overhauser effect spectroscopy and heteronuclear multiple quantum coherence spectroscopy. The 1H/1H connectivities of the protons of each sugar residue in an oligosaccharide were established by two-dimensional homonuclear correlation spectroscopy, while 1H/13C assignments were made using 1H inverse detection. One- and two-dimensional nuclear resonance spectroscopic analysis of these heparin oligosaccharides showed two closely related groups of heparin-oligosaccharides are afforded by enzymatic depolymerization of heparin. One group is fully sulphated, having the structures delta UAp2S(1[-->4)-alpha-D-GlcNpS6S(1-->4)-alpha-L-IdoAp2S( 1]n-->4)-alpha- D-GlcNpS6S, where delta UAp is 4-deoxy-alpha-L-threo-hex-4-eno-pyranosyluronic acid, GlcNp is 2-deoxy-2-aminoglucopyranose, IdoAp is idopyranosyluronic acid, S is sulphate and n = 0-6. The other group of oligosaccharides differ in that they contain beta-D-glucuronic acid in place of the alpha-L-iduronic acid residue nearest to the reducing end. The present study describes the isolation and structural elucidation of seven new oligosaccharides: an octasaccharide, two decasaccharides, two dodecasaccharides and two tetradecasaccharides. The utility of two-dimensional nuclear resonance spectroscopy to determine the structure of complex heparin oligosaccharides is also illustrated.
authors.affiliation: Division of Medicinal and Natural Products Chemistry, College of Pharmacy, University of Iowa, Iowa City 52242, USA.
authors.forename: A
authors.initials: A
authors.lastname: Pervin
authors.forename: C
authors.initials: C
authors.lastname: Gallo
authors.forename: K A
authors.initials: KA
authors.lastname: Jandik
authors.forename: X J
authors.initials: XJ
authors.lastname: Han
authors.forename: R J
authors.initials: RJ
authors.lastname: Linhardt
mesh_terms: D000818:Animals; D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D002850:Chromatography, Gel; D004591:Electrophoresis, Polyacrylamide Gel; D006493:Heparin / Q000737:chemistry* / Q000302:isolation & purification; D007413:Intestinal Mucosa; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009844:Oligosaccharides / Q000737:chemistry* / Q000302:isolation & purification; D013552:Swine
chemical_list: D009844:Oligosaccharides; D006493:Heparin