LATERAL DIFFUSION-COEFFICIENTS OF PHOSPHOLIPIDS IN SPHERICAL BILAYERS ON A SOLID SUPPORT MEASURED BY H-2-NUCLEAR-MAGNETIC-RESONANCE RELAXATION
LATERAL DIFFUSION-COEFFICIENTS OF PHOSPHOLIPIDS IN SPHERICAL BILAYERS ON A SOLID SUPPORT MEASURED BY H-2-NUCLEAR-MAGNETIC-RESONANCE RELAXATION
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DOI：
10.1103/physreve.47.2109
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发表时间：
1993-03-01
影响因子：
2.4
通讯作者：
BAYERL, TM
中科院分区：
文献类型：
--
作者：
KOCHY, T;BAYERL, TM
提出了一种替代的核磁共振（NMR）方法来测量磷脂在固体载体上沿球形双分子层平面的横向扩散系数D。在不同温度下测定了直径为640 nm的球形二氧化硅载体上棕榈酰油酰磷脂酰胆碱（POPC）双分子层的D值。该方法是基于测量不同脉冲间隔时间下carr - purcell - meiboomm - gill （CPMG）脉冲序列得到的四极横向弛豫时间。它利用了CPMG序列可以逐步滤除横向扩散等运动对横向弛豫的贡献，这些运动在核磁共振时间尺度上是缓慢的。该序列与一个新的膜模型系统相结合，在直径明确的球形支撑上的单层双层，可以确定D。我们得到的POPC支撑双层的D值[D=(2.1+/-0.7) X 10(-12) m2/s，在10度- c， D=(4.0+/-0.8) X 10(-12) m2/s，在30度- c，和D=(7.0+/-1.0) X 10(-12) m2/s[50℃]与其他方法如光漂白后荧光恢复（FRAP）和脉冲场梯度核磁共振（PFG-NMR）得到的结果吻合良好。从不同的特征长度和时间尺度上讨论了所得到的D值与最近从准弹性中子散射研究中报道的D值之间的差异。这种核磁共振方法优于FRAP和电子自旋共振方法，因为它不需要在磷脂上附着大块的标签，而且它测量双分子层中所有分子（而不仅仅是探针）的平均扩散。此外，CPMG方法的特征长度尺度明显短于FRAP或PFG-NMR。这些优点为研究模型膜系统相变附近的脱混和畴形成过程提供了潜力。
An alternative nuclear-magnetic-resonance (NMR) method for the measurement of the lateral diffusion coefficient D of phospholipids along the plane of a spherical bilayer on a solid support is presented. D values are determined at various temperatures for palmitoyl-oleoyl-phosphatidylcholine (POPC) bilayer on a spherical silica support of 640 nm diameter. The method is based upon the measurement of the quadrupolar transverse relaxation times obtained by the Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence for a series of different pulse spacing times. It takes advantage of the fact that the CPMG sequence can progressively filter out contributions to the transverse relaxation arising from motions like lateral diffusion, which are slow on the NMR time scale. The combination of this sequence with a new membrane model system, single bilayers on a spherical support of well-defined diameter, enables the determination of D. The D values which we obtain for POPC supported bilayers [D=(2.1+/-0.7) X 10(-12) m2/s at 10-degrees-C, D=(4.0+/-0.8) X 10(-12) m2/s at 30-degrees-C, and D=(7.0+/-1.0) X 10(-12) m2/s at 50-degrees-C] are in good agreement with those obtained by other methods like fluorescence recovery after photobleaching (FRAP) and pulsed-field-gradient NMR (PFG-NMR). The discrepancies between the obtained D values and those reported recently from quasielastic neutron-scattering studies are discussed in terms of the different characteristic lengths and time scales over which the methods are sensitive. This NMR method is superior to FRAP and electron spin resonance methods since it requires no bulky labels attached to the phospholipids and it measures the average diffusion of all molecules (and not only that of the probes) in the bilayer. Moreover, the characteristic length scale of the CPMG method is significantly shorter than for FRAP or PFG-NMR. These advantages give the present method potential for the study of demixing and domain formation processes near phase transitions in model membrane systems.