Abstract
A new method to cleave the double bond of sphingolipids has been developed. Using limited concentrations of KMnO4 and an excess of NaIO4, in a neutral aqueous tert-butanol solvent system gave nearly quantitative yields of the oxidized product. A variety of natural glycosphingolipids (GSLs): GlcC, GalC, SGC, LC, Gb3C, Gb4C, Gg4C, Gb5C, and GM1C, gave the corresponding acids: 2-hydroxy-3-(N-acyl)-4-(O-glycosyl)-oxybutyric acids, i.e. "glycosyl ceramide acids" (GSL.CCOOH) in excellent yields (80-90%). Deacyl GSLs (dGSLs) were oxidized to acids containing the oligosaccharides devoid of hydrocarbon chains, i.e. "ceramide oligosaccharides" (dGSL. NRR1CCOOH, where R = R1 = H; R = H, R1 = CH3CO; or R = R1 = Me). The efficacy of this method was demonstrated by transforming natural GSLs: GlcC, GalC, GalS, SGC, LC, Gb3C, and Gb4C into neoglycoproteins via coupling glycosyl ceramide acids (except GalS, which was coupled directly) to bovine serum albumin (BSA). Mass spectroscopic analysis of GalC-BSA conjugates, (GalC.CONH)nBSA and (GalS.NHCO)nBSA gave a value of 9 +/- 1 and 16 +/- 2 for n. Neoglycoconjugates derived from GlcC, GalC (type I and II and the behenic analog), SGC, LC, and Gb3C were recognized by the recombinant human immunodeficiency virus coat protein gp120 (rgp120). The GalS conjugate showed significantly reduced binding, and the Gb4C conjugate showed no binding. Thus, rgp120/GSL-BSA interaction requires a terminal galactose and/or glucose residue. Terminal N-acetylgalactosamine containing GSLs are not bound. The ceramide acid conjugates provide a more effective scaffold for presentation of glycone for rgp120 binding than those derived from dGSLs. The retention of receptor specificity of the glycoconjugates was validated by retention of the expected binding specificity of VT1 and VT2e for Gb3C and Gb4C conjugates, respectively. These studies open a new vista in the generation of glycoconjugates from GSLs and further emphasize the role of aglycone in glycolipid recognition.
Highlights
A new method to cleave the double bond of sphingolipids has been developed
Deacyl GSLs were oxidized to acids containing the oligosaccharides devoid of hydrocarbon chains, i.e. “ceramide oligosaccharides”. The efficacy of this method was demonstrated by transforming natural GSLs: glucosyl ceramide (GlcC), GalC, GalS, sulfogalactosyl ceramide (SGC), lactosyl ceramide (LC), Gb3C, and Gb4C into neoglycoproteins via coupling glycosyl ceramide acids to bovine serum albumin (BSA)
Neoglycoconjugates derived from GlcC, GalC, SGC, LC, and Gb3C were recognized by the recombinant human immunodeficiency virus coat protein gp120
Summary
A new method to cleave the double bond of sphingolipids has been developed. Using limited concentrations of KMnO4 and an excess of NaIO4, in a neutral aqueous tert-butanol solvent system gave nearly quantitative yields of the oxidized product. “ceramide oligosaccharides” (dGSL1⁄7NRR1CCOOH, where R ؍R1 ؍H; R ؍H, R1 ؍ CH3CO; or R ؍R1 ؍Me) The efficacy of this method was demonstrated by transforming natural GSLs: GlcC, GalC, GalS, SGC, LC, Gb3C, and Gb4C into neoglycoproteins via coupling glycosyl ceramide acids (except GalS, which was coupled directly) to bovine serum albumin (BSA). Our attempts to use KMnO4-crown ether-benzene system to oxidize dGSLs (GalS or Gb3S) gave the ceramide oligosaccharides in very low yields, GSL; BSA, bovine serum albumin; PAGE, polyacrylamide gel electrophoresis; TBS, Tris-buffered saline; HPTLC, high performance thin layer chromatography; DCM, dichloromethane; t-BuOH, tert-butyl alcohol; isoPrOH, iso-propyl alcohol; DCE, 1,2-dichloroethane; Py, pyridine; Et2O, diethyl ether; Bz, benzene; M, methanol; C, chloroform; A, acetone; NHS, N-hydroxysuccinimide; EDAC, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide; MALDI-TOF, matrix-assisted laser desorption ionization/time-of-flight; FAB, fast atom bombardment; HIV, human immunodeficiency virus; ES, Electro Spray
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.