gistfile1.txt

https://www.biostars.org/p/299307/#9562241 

We have taken to preparing recombinant Tn5 now as it's much cheaper than commercial suppliers, whether that is unloaded or loaded. The latest batch which was particularly highly concentrated around 1.5 mg/ml led to very strong activity so much so we had to dilute the Tn5 protein 1/3 to 1/6 before loading with either Nextera or our own custom adapters. I worried there might be some nuclease carry-over from the bacterial expression system to explain why it's so much stronger than previous productions, so I included an unloaded Tn5 at the same dilution as a negative control. Well turns out this doesn't work well as a negative control because even unloaded Tn5 fragmented test lambda DNA input. Surprisingly this was even stronger than Tn5 loaded with adapters.

I tested both old and new productions of Tn5 and Tn5 from Creative Enzymes and Diagenode (purchased both unloaded versions). I contacted Diagenode and they state that they actually test the nuclease activity of unloaded Tn5 without loading adapters. Please see the tweet.