The unconjugated FITC is unstable for longer period even it dissolved in DMSO and this need to be subjected for conjucation immediately. Further it's light sensitive, the conjugation process to be carried out under dark condition.

I hope you are using casein tagged FITC (commercially available) for your research work and that's not requires any FITC tagging and purification protocols.

You may reconstitute the caseinFITC in PBS buffer (pH 7.4) instead of ddH2O and store it at -80 C untill the use.

Prepare the caseinFITC in multiple vials and freeze it. Use a vial per test (it's not advisable to re-freeze the thawed taggedFITC).

The working concentration of the taggedFITC can be arrived by performing the staining procedure with different dilutions.

Sekar Thangaraj thank you for the answer!

Could you provide more explanation about "You may reconstitute the caseinFITC in PBS buffer (pH 7.4) instead of ddH2O and store it at -80 C untill the use."

If is there any data that shows the storage did not effected caseinFITC, That would be very helpful. (and yes i am using commercial caseinFITC).

Hi Elif Oztemiz Topcu,

I am using the FITC for the rabies virus staining in cell culture.

We procure the untagged molecules of FITC and tagging with purified rabies specific antibody in our laboratory and purifying with SephadexG50 column. The final elution of tagged FITC carried out with PBS (pH7.4), aliquated in to cryo vials and stored at -40/ -80 until further use. Its working good upto one year. use. Its working up

you may gothrough the following paper that will give some information (full article in my Research gate profile)

Quantification of Rabies Virus by Real Time PCR

in comparison with Mouse Inoculation Test (MIT)

and Fluorescent Antibody Test (FAT).

Comparative analysis of MEM, RPMI 1640 media on rabies virus propagation in vero cell and virus quantification by FAT.

Sekar Thangaraj thank you very much. this is very helpful!