title: Raman spectroscopic study of semisynthetic species of cerebroside sulfate: two types of hydrocarbon chain interdigitation.
abstract: Raman spectroscopy was used to study the phase behavior of several semisynthetic species of the acidic glycosphingolipid cerebroside sulfate (CBS) which occur in myelin. The C-H stretching mode region at 2800-3100 cm-1 of C18:0-CBS, C24:0-CBS, and C26:0-CBS, and the alpha-hydroxy fatty acid species C18:0h-CBS, was studied in the presence of 2 M Li+ and 2 M K+. Earlier studies have shown that K+ shields the negative charge on the sulfate more effectively than Li+, thus promoting intermolecular hydrogen-bonding interactions between the lipid molecules. Indeed, a novel broad background feature was present in the Raman spectra from 2900 to 3200 cm-1, which was attributed to O-H stretch associated with intermolecular hydrogen bonding between lipid hydroxyl groups. After subtraction of this broad feature, the intensities of the lipid C-H stretching vibrational transitions could be determined. These indicated that in K+, the degree of order (intrachain conformation and lateral chain-chain interactions) of C18:0-CBS, whose hydrocarbon region is fairly symmetrical in chain length, is similar to that of the symmetric chain length glycerolipid dipalmitoylphosphatidylcholine, while the degree of order is lower in Li+, as a result of the increased lateral charge repulsion of the head groups in Li+. Two phase transitions were observed for the highly asymmetric species C24:0-CBS and C26:0-CBS in K+ but only one transition in Li+.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Physics, Memorial University of Newfoundland, St. John's, Canada.
authors.forename: C C
authors.initials: CC
authors.lastname: Stevenson
authors.forename: N H
authors.initials: NH
authors.lastname: Rich
authors.forename: J M
authors.initials: JM
authors.lastname: Boggs
mesh_terms: D000818:Animals; D002244:Carbon / Q000737:chemistry; D002417:Cattle; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D005227:Fatty Acids / Q000737:chemistry; D005699:Galactosylceramides / Q000737:chemistry*; D006859:Hydrogen / Q000737:chemistry; D008094:Lithium / Q000494:pharmacology; D010100:Oxygen / Q000737:chemistry; D011188:Potassium / Q000494:pharmacology; D013059:Spectrum Analysis, Raman; D013696:Temperature
chemical_list: D005227:Fatty Acids; D005699:Galactosylceramides; D002244:Carbon; D006859:Hydrogen; D008094:Lithium; D011188:Potassium; D010100:Oxygen