Assessment of REase activity in CR.NsoJS138I. A comparison was made between commercial R.PvuII and CR.NsoJS138I. Enzymes were incubated for 1h with DNA from bacteriophage λ. Four different reaction buffers were used, and in each buffer four temperatures were used. Reactions were resolved on agarose-TBE gels containing ethidium bromide (see Methods for details). Inset: Left-to-right: markers, uncut pUC19, pUC19 cut with CR.NsoJS138I or PvuII at 37°, pUC19 cut with CR.NsoJS138I at 30°.