Stevenson C C, Rich N H, Boggs J M
Department of Physics, Memorial University of Newfoundland, St. John's, Canada.
Biochemistry. 1992 Feb 18;31(6):1875-81. doi: 10.1021/bi00121a041.
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)
拉曼光谱法被用于研究髓鞘中存在的几种酸性糖鞘脂脑硫脂（CBS）半合成物种的相行为。在2 M Li⁺和2 M K⁺存在的情况下，研究了C18:0-CBS、C24:0-CBS和C26:0-CBS以及α-羟基脂肪酸物种C18:0h-CBS在2800 - 3100 cm⁻¹处的C-H伸缩振动模式区域。早期研究表明，K⁺比Li⁺更有效地屏蔽硫酸根上的负电荷，从而促进脂质分子间的分子间氢键相互作用。实际上，在2900至3200 cm⁻¹的拉曼光谱中出现了一个新的宽背景特征，这归因于与脂质羟基之间分子间氢键相关的O-H伸缩。减去这个宽特征后，可以确定脂质C-H伸缩振动跃迁的强度。这些表明，在K⁺中，碳氢区域链长相当对称的C18:0-CBS的有序程度（链内构象和侧链-链相互作用）与对称链长的甘油脂质二棕榈酰磷脂酰胆碱相似，而在Li⁺中有序程度较低，这是由于Li⁺中头部基团的侧向电荷排斥增加。在K⁺中观察到高度不对称的物种C24:0-CBS和C26:0-CBS有两个相变，而在Li⁺中只有一个相变。（摘要截断于250字）
