Water exchange across the erythrocyte plasma membrane studied by HR-MAS NMR spectroscopy
Water exchange across the erythrocyte plasma membrane studied by HR-MAS NMR spectroscopy
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DOI：
10.1002/mrm.21054
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发表时间：
2006-11-01
影响因子：
3.3
通讯作者：
Aime, Silvio
中科院分区：
文献类型：
--
作者：
Bruno, Erik;Digilio, Giuseppe;Aime, Silvio
利用高分辨魔角自旋（HR-MAS）核磁共振波谱研究了红细胞（RBC）跨质膜的水交换。在HR-MAS条件下，离心力导致RBC悬浮液分裂成由无细胞水的中心核和紧密堆积的细胞的外层组成的两相系统。属于这些相中的每一相的水产生两个分离的共振。由于相之间的物理分离，它们之间的化学交换在化学位移或饱和转移（ST）NMR时间尺度上是不可检测的。当红细胞被分散和固定在由交联白蛋白制成的基质中时，防止分裂成两相系统，并且在H-1 HR-MAS NMR光谱中检测到水的单个交换平均峰。该峰的线形取决于跨膜交换动力学，因为MAS使所有各向异性磁相互作用平均化，所述各向异性磁相互作用在常规液体条件下负责额外的谱线加宽。根据双位点交换模型的线形分析产生了细胞内隔室内的水分子的大约10 ms（在37 ° C下）的停留寿命，这与普遍接受的9.6-14.8 ms的值相差不远。
Water exchange across the plasma membrane of erythrocytes (red blood cells (RBCs)) was studied by means of high-resolution magic angle spinning (HR-MAS) NMR spectroscopy. Under HR-MAS conditions, the centrifugal force causes the splitting of RBC suspensions into a two-phase system composed of a central core of cell free water and an outer layer of tightly packed cells. Water belonging to each of these phases gives rise to two separated resonances. Chemical exchange between them is not detectable on the chemical shift or saturation transfer (ST) NMR time scale because of the physical separation between the phases. When the RBCs are dispersed and immobilized within a matrix made of cross-linked albumin, the splitting into a two-phase system is prevented and a single exchange-averaged peak for water is detected in H-1 HR-MAS NMR spectra. The lineshape of this peak is dependent on transmembrane exchange kinetics, since MAS averages out all the anisotropic magnetic interactions that are responsible for additional line-broadening under conventional liquid conditions. Line-shape analysis according to a two-site exchange model yielded a residence lifetime on the order of about 10 ms (at 37 degrees C) for a water molecule within the intracellular compartment, which is not too far from the generally accepted value of 9.6-14.8 ms.