Gupta R K, Gupta P, Yushok W D, Rose Z B
Biochem Biophys Res Commun. 1983 Nov 30;117(1):210-6. doi: 10.1016/0006-291x(83)91562-0.
To resolve a controversy in the literature concerning the affinity of Mg++ for ATP to be used in our noninvasive 31P NMR procedure for the determination of free Mg++ in living cells, we have reinvestigated the apparent dissociation constant of MgATP under physiologic ionic conditions and over the cellular range of ATP concentrations by a combination of NMR and optical absorbance techniques. The new combination method utilizes 31P NMR chemical shifts to determine the degree of Mg++ chelation of ATP in a solution containing free ATP and MgATP, and uses a properly calibrated indicator dye, antipyrylazo III, for optical measurement of free Mg++ in the same solution. The data yield an average value of 50 +/- 10 microM for the apparent dissociation constant of MgATP which indicates low levels of free Mg++ (less than 1 mM) in several different types of tissues, including perfused heart muscle, contrary to a recent report in the literature.
为解决文献中关于Mg++与ATP亲和力的争议，以便用于我们测定活细胞中游离Mg++的非侵入性31P NMR程序，我们通过NMR和光吸收技术相结合的方法，重新研究了生理离子条件下及细胞内ATP浓度范围内MgATP的表观解离常数。这种新的组合方法利用31P NMR化学位移来确定含有游离ATP和MgATP的溶液中ATP的Mg++螯合程度，并使用经过适当校准的指示剂染料安替比拉宗III对同一溶液中的游离Mg++进行光学测量。数据得出MgATP表观解离常数的平均值为50±10微摩尔，这表明在包括灌注心肌在内的几种不同类型组织中游离Mg++水平较低（低于1毫摩尔），这与文献中最近的一份报告相反。
