Magic-angle spinning NMR studies of molecular organization in multibilayers formed by 1-octadecanoyl-2-decanoyl-sn-glycero-3-phosphocholine.
Magic-angle spinning NMR studies of molecular organization in multibilayers formed by 1-octadecanoyl-2-decanoyl-sn-glycero-3-phosphocholine.
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1-十八酰基-2-癸酰基-sn-甘油-3-磷酸胆碱形成的多层分子组织的魔角旋转核磁共振研究。
DOI：
10.1016/s0006-3495(90)82490-5
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发表时间：
1990
影响因子：
3.4
通讯作者：
Bittman,R
中科院分区：
文献类型：
--
作者：
Halladay,HN;Stark,RE;Ali,S;Bittman,R
采用魔角旋转1H和13 C核磁共振（NMR）研究了50%重量的1-十八酰基-2-癸酰基-sn-甘油基-3-磷酸胆碱（C[18]：C[10]PC）和1-十八酰基-2-d19-癸酰基-PC（C[18]：C[10]PC-d19）的水分散体，这两种混合链磷脂可形成交叉多层膜。胆碱头基的甲基质子的1H NMR线宽已被用于监测液晶到凝胶（LC到G）的相变，并确认冻结和熔化温度之间的变化。1H和13 C自旋-晶格弛豫时间都表明，与LC状态下的双链物种相比，C（18）：C（10）PC在兆赫频率下对链段重取向的限制是不寻常的;然而，混合链磷脂的每个化学部分都表现出可归类为类液体的运动行为。C（18）：C（10）PC和C（18）：C（10）PC-d19的二维核奥弗豪泽光谱（NOESY）揭示了C18链的ω-甲基质子和磷酸胆碱头基的N-甲基质子之间的交叉峰，一些实验和理论考虑反对基于自旋扩散的解释。使用NMR弛豫时间和NOESY连通性沿着，以及四自旋系统的计算形式（Keepers，J.W.，和T. L. James. 1984. J.磁共振57：404-426），获得C18链的ω-甲基质子与磷酸胆碱头基的N-甲基质子之间的平均距离的估计值。这一发现与交叉结合的程度相一致，该交叉结合的程度类似于对具有广泛不同的酰基链长度的凝胶状态磷脂酰胆碱分子的有组织组装提出的交叉结合的程度（Hui，S. W.，和C. H.煌1986.生物化学。25：1330-1335）;然而，酰基链回弯或其他分子间相互作用也可能有助于NOESY结果。对于多层C（18）：C（10）PC在凝胶相，13 C化学位移测量表明，反式构象占主导地位的沿着两个酰基链。13 C自旋晶格弛豫时间证实了LC状态中注意到的不寻常的运动限制;然而，13 C和1H双指框架弛豫时间表明，叉指排列增强了在中千赫兹频率下发生的链或双层运动。
Magic-angle spinning 1H and 13C nuclear magnetic resonance (NMR) have been employed to study 50%-by-weight aqueous dispersions of 1-octadecanoyl-2-decanoyl-sn-glycero-3-phosphocholine (C[18]:C[10]PC) and 1-octadecanoyl-2-d19-decanoyl-PC (C[18]:C[10]PC-d19), mixed-chain phospholipids which can form interdigitated multibilayers. The 1H NMR linewidth for methyl protons of the choline headgroup has been used to monitor the liquid crystalline-to-gel (LC-to-G) phase transition and confirm variations between freezing and melting temperatures. Both 1H and 13C spin-lattice relaxation times indicate unusual restrictions on segmental reorientation at megahertz frequencies for C(18):C(10)PC as compared with symmetric-chain species in the LC state; nevertheless each chemical moiety of the mixed-chain phospholipid exhibits motional behavior that may be classified as liquidlike. Two-dimensional nuclear Overhauser spectroscopy (NOESY) on C(18):C(10)PC and C(18):C(10)PC-d19 reveals cross-peaks between the omega-methyl protons of the C18 chain and the N-methyl protons of the phosphocholine headgroup, and several experimental and theoretical considerations argue against an interpretation based on spin diffusion. Using NMR relaxation times and NOESY connectivities along with a computational formalism for four-spin systems (Keepers, J. W., and T. L. James. 1984. J. Magn. Reson. 57:404–426), an estimate of 3.5 A is obtained for the average distance between the omega-methyl protons of the C18 chain and the N-methyl protons of the phosphocholine headgroup. This finding is consistent with a degree of interdigitation similar to that proposed for organized assemblies of gel-state phosphatidylcholine molecules with widely disparate acyl-chain lengths (Hui, S. W., and C.-H. Huang. 1986. Biochemistry. 25:1330–1335); however, acyl-chain bendback or other intermolecular interactions may also contribute to the NOESY results. For multibilayers of C(18):C(10)PC in the gel phase, 13C chemical-shift measurements indicate that trans conformers predominate along both acyl chains. 13C Spin-lattice relaxation times confirm the unusual motional restrictions noted in the LC state; nevertheless, 13C and 1H rotating-frame relaxation times indicate that the interdigitated arrangement enhances chain or bilayer motions which occur at mid-kilohertz frequencies.