Transmembrane ion pumping: high resolution cation NMR spectroscopy.
Transmembrane ion pumping: high resolution cation NMR spectroscopy.
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跨膜离子泵送：高分辨率阳离子核磁共振波谱。
DOI：
10.1111/j.1749-6632.1987.tb32900.x
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发表时间：
1987
影响因子：
5.2
通讯作者：
SpringerJr,CS
中科院分区：
文献类型：
--
作者：
SpringerJr,CS
碱金属阳离子Na+和K+在生命系统中普遍存在。它们主要以游离的水阳离子形式存在，其生物化学本质在于它们在细胞膜上的不均匀分布及其随后的跨膜转运。钠强烈（尽管不是完全）被大多数细胞排除在外，并且Na+梯度中储存的能量主要用于驱动小分子和其他离子的主动跨膜转运，或者在可兴奋细胞中，用于瞬时减小或消除跨膜电位。在一个有趣的自然形式逆转中，K+集中在大多数细胞中，并且其梯度主要用于维持该电位，这是大多数细胞所表现的。2因此，这些分布中的每一种对于细胞活力都是至关重要的，并且由位于大多数细胞的细胞质膜中的主动转运系统维持。“在本文中，我们使用术语离子泵的意义就是：Na+和/或K+离子克服其电化学电位梯度穿过膜的（主动）运输。在许多情况下，这是通过膜酶的作用来实现的，膜酶是所有酶中最普遍的酶之一。生理学和生物物理学的一个重要目标是在真实的时间内尽可能无创地监测整个组织中这些离子梯度的维持和恢复。这表明需要光谱方法。不幸的是，Na+和K+离子的封闭电子壳层排除了灵敏的光学或电子顺磁共振光谱的使用。幸运的是，钠（23 Na，100%，I= 3/2）和钾（39 K，93%，I= 3/2）的最丰富、最稳定的同位素具有核磁共振矩，并且对核磁共振（NMR）光谱敏感。本文综述了组织样品的~（23）Na和~（39）K核磁共振研究。考虑到~（23）Na的核磁特性，沿着Na+在生命系统中的丰度，我们认识到~（23）Na是迄今为止生物学中第二大核磁共振敏感核（~ 1H是第一大）。这引起了相当大的组织光谱活动超过三十年的时间，并在医疗23钠核磁共振成像最近的强烈兴趣。[5]早期的光谱学研究揭示了两个基本问题。首先，来自组织中各个区室的23 Na信号是等熵的。由于Na+离子主要以含水物质的形式存在，无论含有它们的隔室如何，它们的化学位移实际上是不可区分的。第二，积分的Na光谱强度通常与总量的预期强度不对应
The alkali metal cations Na+ and K+ are ubiquitous in living systems. They are mostly present as free aquo cations and the essence of their biochemistry lies in their unequal distributions across cell membranes and their subsequent transmembrane transport. Sodium is strongly (though not totally) excluded from most cells and the energy stored in the Na+ gradient is used mostly to drive the active transmembrane transport of small molecules and other ions' or, in excitable cells, to transiently diminish or eliminate the transmembrane electrical potentiaL2 In an interesting natural reversal of form, K+ is concentrated in most cells and its gradient is used mostly to maintain this potential, which is exhibited by most cells. 2 Each of these distributions is thus crucial for cell viability and is maintained by an active transport system located in the cytoplasmic membrane of most cells.-'The sense in which we use the term ion pumping in this paper is just this: the (active) transport of Na+ and/or K+ ions across a membrane against their electrochemical potential gradients. In many cases, this is accomplished by the action of the membrane enzyme," a++ K+]-ATPase, one of the most ubiquitous of all enzymes4 An important goal in physiology and biophysics is to monitor the maintenance and restoration of these ion gradients in whole tissue in real time and as noninvasively as possible. This indicates that a spectroscopic approach is called for. Unfortunately, the closed electronic shells of the Na+ and K+ ions preclude the use of the sensitive optical or electron paramagnetic resonance spectroscopies. Fortunately, the most abundant, stable isotopes of sodium (23Na, loo%, I= 3/2) and potassium (39K, 93%, I= 3/2) have nuclear magnetic moments and are susceptible to nuclear magnetic resonance (NMR) spectroscopy. We have recently reviewed the study of 23Na and 39K NMR of tissue~ arnples.~ Considering the nuclear magnetic properties of 23Na, along with the abundance of Na+ in living systems, leads to the realization that 23Na is by far the second most NMR-sensitive nucleus ('H is the first) in bi~ logy.~ This has given rise to considerable tissue spectroscopic activity over a thirty-year period and to a more recent intense interest in medical 23Na NMR imaging. 5 The early spectroscopic studies revealed two fundamental problems. First, the 23Na signals from the various compartments in tissue are isochronous. Since the Na+ ions are mostly in the form of the aquo species, irrespective of the compartment containing them, their chemical shifts are effectively indistinguishable. Second, the integrated'-'Na spectral intensity often does not correspond to that expected for the total amount