Clark A F, Swanson P D, Stahl W L
J Biol Chem. 1975 Dec 25;250(24):9355-9.
Several cardiotonic steroids have been modified by reduction of the unsaturated lactone and their interactions with the sodium- and potassium-activated ATPase ((Na+ + K+)-ATPase) have been investigated. Reduction of the unsaturated lactone results in a decrease in binding affinity due primarily to an increase in the dissociation rate constant concomitant with a decrease in the activation free energy of dissociation. This decrease in activation free energy is about 2 to 4 kcal, which is approximately equal to the energy of one hydrogen bond. It is suggested that the increase in dissociation rate due to reduction of the unsaturated lactone may make possible the use of these compounds as affinity ligands for purification of the (Na+ + K+)-ATPase or an ouabain-binding fragment.
几种强心甾类化合物已通过不饱和内酯的还原进行了修饰，并对它们与钠钾激活的ATP酶（（Na+ + K+）-ATP酶）的相互作用进行了研究。不饱和内酯的还原导致结合亲和力降低，这主要是由于解离速率常数增加，同时解离活化自由能降低。这种活化自由能的降低约为2至4千卡，大约等于一个氢键的能量。有人提出，由于不饱和内酯的还原导致解离速率增加，可能使这些化合物用作纯化（Na+ + K+）-ATP酶或哇巴因结合片段的亲和配体成为可能。
