Bitan:Calculating specific activity of hot CTP after calibration date

Calculating the specific activity of α-³²P-CTP after the calibration date
CTP used is from Perkin Elmer: CTP, α-³²P- 3000 Ci/mmol, 10 mCi/ml , 250 µCi.

Reference date for this lot was 11/21/09. The activity calculated for this lot on 11/27/09 is as follows:

This is CTP lot was 6 days old. The activity of α-³²P-CTP, lot RSO0117175 was 0.748 of total activity on 11/27/09 based on the decay chart

here.

According to this formula, the total activity was calculated to be 2447 Ci/mmol on 11/27/09:

where SA_theo.=9120 for the theoretical specific activity of carrier-free ³²P; SA_cal.=specific activity after the calibration date; and D_F is the fraction of current radioactivity that will remain on the calibration date from the Decay Chart. So in this case

.

After the reference date, the total activity of the fresh hot CTP was 250 μCi in 25 μl, and the concentration was 10 μCi/μl (10 mCi/ml). But now, it is 187 μCi because 0.748×250=187. If 4 μl is used for in-vitro transcription reaction, the total amount used would be 4×187 μCi/25μl= 29.92=30 μCi for each reaction.

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