I have a stock of 10 mg DNAse which is analyzed by the supplier to have more than 400 Kunitz per mg. My (final) target concentration is 200 U per ml, which is - as far as I understood - a different way of measuring the activity of the enzyme. Is there any chance to convert the units into each other? How?
Hi Simon
From Worthington manual of enzymes.
"As measured at Worthington, one Kunitz unit digests 1µg of lambda DNA in 10 minutes at 37°C in 50mM Tris, 1mM Mg2+, 1mM Ca2+, pH 7.8 in a 50µl reaction. Correlation of digestion units with Kunitz units is different for other DNA and buffer systems."
Hope this helps.
GFS
Yes thanks, that helped. However, I did not convert the units though. I think U is not really working with DNAse, beacause it is a unit working with moles, which I find difficult when dealing with DNA (correct me if I am mistaking here). But I did some new calculations about how much DNAse would be needed in my case and ended up with 13.2 Kunitz/ml (corresponding to 33 µg enzyme per ml). Does that sound reasonable? Is high DNAse concentration toxic to cells (it will be with the cells for 5 min only)?
Thanks again,
Simon
Hi,
I have a question regarding this Kunitz units conversion. I have 1500kunitz units of lyophilized powder from Qiagen and I want to incubate my tissue sections which I will be using for my TUNEL (I mean I want to treat them with DNAse to serve as a positive control). So the TUNEL protocol says I need 3000U/ml of DNAse 1 in 50mM Tis -HCL, ph=7.5, 1mg/mL BSA. I am still not clear how to do this conversion????
Hi Rupali Sharma,
now I am exactly in the same situation as you. Did you finally found some interesting solution to carry out the TUNEL protocol with DNAse I as a positive control?
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