Williams E C, Cordes E H
Biochemistry. 1976 Dec 28;15(26):5792-9. doi: 10.1021/bi00671a016.
Whole bovine white matter yields a poorly resolved natural abundance 13C nuclear magnetic resonance (NMR) spectrum. The spectrum principally reflects carbon atoms of the constituent membrane lipids: several resonances could be specifically assigned but no resonances attributable to cholesterol are detectable. Except for the methyl group at the terminus of fatty acyl chains, lipid carbons giving rise to the 13C NMR spectrum have values of spin-lattice relaxation time between 140 and 500 ms, indicating significant restrictions on segmental and rotational mibolities but consistent with a generally fluid structural organization. The 13C NMR spectrum of myelin isolated from bovine white matter is similar to that for the whole white matter itself. In both white matter and isolated meylin, the integrated intensities for several carbon atoms are considerably less than those for the same carbon atoms in total lipid extracts. The data for white matter and myelin are consistent with a model in which observed line broadening is due to restrictions in the amplitude of chain flexing rather than to severe restrictions on chain segmental motion. Failure to detect resonances of cholesterol ring system carbon atoms may reflect marked anisotropy of rotational reorientation.
完整的牛白质产生的自然丰度13C核磁共振（NMR）谱分辨率较差。该谱主要反映组成膜脂的碳原子：几个共振峰可以明确归属，但未检测到可归因于胆固醇的共振峰。除了脂肪酰链末端的甲基外，产生13C NMR谱的脂质碳的自旋晶格弛豫时间值在140至500毫秒之间，这表明对链段运动和旋转运动有显著限制，但与总体流体结构组织一致。从牛白质中分离出的髓磷脂的13C NMR谱与整个白质本身的谱相似。在白质和分离出的髓磷脂中，几个碳原子的积分强度都明显低于总脂质提取物中相同碳原子的积分强度。白质和髓磷脂的数据与一个模型一致，在该模型中，观察到的谱线展宽是由于链弯曲幅度的限制，而不是由于对链段运动的严重限制。未能检测到胆固醇环系统碳原子的共振峰可能反映了旋转重取向的显著各向异性。
