Minta A, Tsien R Y
Department of Physiology-Anatomy, University of California, Berkeley 94720.
J Biol Chem. 1989 Nov 15;264(32):19449-57.
Fluorescent indicators sensitive to cytosolic concentrations of free Na+ have been synthesized and characterized. They consist of a crown ether, 1,7-diaza-4,10,13-trioxacyclopentadecane, linked via its nitrogens to fluorophores bearing additional liganding centers. In the currently preferred dye, SBFI (short for sodium-binding benzofuran isophthalate), the fluorophores are benzofurans linked to isophthalate groups. Selectivities for Na+ over K+ of about 20 are observed, resulting in effective dissociation constants for Na+ of about 20 mM against a background of 120 mM K+. Increasing [Na+] increases the ratio of excitation efficiency at 330-345 nm to that at 370-390 nm with emission collected at 450-550 nm, so that ratio fluorometry and imaging can be performed with the same wavelengths as used with the well known Ca2+ indicator fura-2. If the macrocyclic ring is increased in size to a 1,10-diaza-4,7,13,16-tetraoxacyclooctadecane, the chelators become selective for K+ over Na+.
已合成并表征了对游离钠离子胞质浓度敏感的荧光指示剂。它们由冠醚1,7 - 二氮杂 - 4,10,13 - 三氧杂环十五烷组成，通过其氮原子与带有额外配位中心的荧光团相连。在当前优选的染料SBFI（钠结合苯并呋喃间苯二甲酸酯的缩写）中，荧光团是与间苯二甲酸酯基团相连的苯并呋喃。观察到钠离子对钾离子的选择性约为20，在120 mM钾离子的背景下，钠离子的有效解离常数约为20 mM。随着[钠离子]的增加，在450 - 550 nm处收集发射光时，330 - 345 nm处的激发效率与370 - 390 nm处的激发效率之比增加，因此比率荧光测定法和成像可以使用与著名的钙离子指示剂fura - 2相同的波长进行。如果大环尺寸增加到1,10 - 二氮杂 - 4,7,13,16 - 四氧杂环十八烷，螯合剂对钾离子的选择性将高于钠离子。
