Klenow (3′-5′ exo-)

SS Exonuclease: 500U <0.1% released DS Exonuclease: 500U <0.1% released Endonuclease: 500U <0.1% converted E. coli 16S rDNA Contamination 500U <10 copies

Unit Characterization Assay Unit activity was measured using a 2-fold serial dilution method. Dilutions of enzyme were made in a glycerol (50%) containing Klenow (3′→5′ exo-) storage solution ([Klenow] f = 0.12-0.002 μg/μl) and added to 50 μL reactions containing 4 μg Calf Thymus DNA, 1X Blue Buffer, 4m Ci/ml 3 H-dTTP and 100 μM dNTPs. Reactions were incubated 10 minutes at 37°C, plunged on ice, and analyzed using the method of Sambrook and Russell (Molecular Cloning, v3, 2001, pp. A8.25-A8.26) . SDS-Page (Physical Purity Assessment) 2.0 μl of concentrated enzyme solution was loaded on a denaturing 4-20% Tris-Glycine SDS-PAGE gel flanked by a broad-range MW marker and 2.0 μl of a 1:100 dilution of the sample. Following electrophoresis, the gel was stained and the samples compared to determine physical purity. The acceptance criteria for this test requires that the aggregate mass of contaminant bands in the concentrated sample do not exceed the mass of the protein of interest band in the dilute sample, confirming greater than 99% purity of the concentrated sample. Protein Concentration (OD 280) Measurement A 3.0 μl sample of enzyme was analyzed at OD 280 using a Nanodrop ND-1000 spectrophotometer standardized using a 2.0 mg/ml BSA sample (Pierce Cat #23209) and blanked with product storage solution. The observed average measurement of 3 replicate samples was converted to mg/ml using an extinction coefficient of 55,450 and molecular weight of 68,067 Daltons. Acceptance for this assay is +/- 5% of reference sample.