Fluo-4, Pentapotassium Salt

Fluo-4 is an analog of Fluo-3 with the two chlorine substituents replaced by fluorines, which results in increased fluorescence excitation at 488 nm that gives higher fluorescence signal. Fluo-4 has its absorption maximum at 494 nm, thus making it excitable by the argon-ion laser. Fluo-4 is essentially nonfluorescent without Ca² present, but the fluorescence increases at least 100 times on Ca² binding. Also, because Fluo-4 binds Ca² more weakly (higher Kd) than do fura-2 and indo-1, it is more useful for measuring high transient Ca² concentration during Ca2 spikes. </p> Fluo-4, pentapotassium is membrane-impermeant, but can be loaded into cells via microinjection or scrape loading. We also cell a membrane-permeant version, Fluo-4 AM Ester. </p> <ul> </p> <li>K_d: ~335 nM</li> </p> <li> lamba;_{Ex/ lamba;Em (low or high [Ca²]) = 494nm/516nm}</li> </p> <li> epsilon;(494 nm) = 82,000 M^-1cm^-1</li> </p> <li>Orange solid soluble in DMSO and water (pH gt;6)</li> </p> <li>Store at 4°C. Protect from light, especially when in solution</li> </p> <li>C₃₆H_{25<span style="font-size: 16px;">F</span>}₂K₅N₂O₁₃</li> </p> <li>MW: 927.09</li> </p> </ul>