Dear Isabel, FITC solutions should be prepared always fresh! You can use FITC stock solution on the same day, preferably within 2-3 hours. Do not ruin your antibody with old FITC! The FITC is much cheaper than the antibody! If you do not want to waste to much FITC, and it is difficult to weigh out 1 or 2 mg FITC, instead of weighing, you can determine the FITC concentration by OD measurements. Take a few crystals of FITC, prepare FITC stock solution (we prefer to use DMSO as solvent), make a dilution and measure the OD at 495 nm. You can use the molar absorption coefficient given in the Molecular probes. Another suggestion: We switched from FITC to X-fluorescein-succinimidylesters and we got better labeling ratios, and higher quantum efficiencies. Lately, we tried the Alexa dyes, and we obtain even better results. (Especially for the rhodamine analogs.) Best regards Janos At 09:46 AM 8/6/99 +0200, you wrote: > >Hello, >Does anyone have any experience with the storage of unconjugated FITC >(isomer 1, Sigma, F7250) ? I have dissolved it in PBS, pH8, 0.1mg/ml >and I keep it in the dark at 3-4°C. Does anyone know something about >the stability in this form and how long it can be stored like this ? > >Thanks >Isabel > Janos Szollosi Department of Biophysics and Cell Biology University Medical School of Debrecen Nagyerdei krt. 98, P.O.Box 39, H-4012 Debrecen, HUNGARY Fax/Phone: (36) (52) 412-623 e-mail: szollo@jaguar.dote.hu
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