RA preparation:
RA should be manipulated in dark. Tubes must be protected from light (using opaque tubes of covering them with foil).
Thaw a RA aliquot (10 mM) at RT (usually takes some time) and make a 1:10 dilution (up to 1 mM) in Ethanol 100%. Divide in handy aliquots and store at -20 ºC.
Add 500 µl of 1mM RA to a 500 ml culture media (Final concentration 1µM RA).