Figure 4. The effect of common buffer components on the LRET assay.

Common buffer components were tested for their ability to alter the interaction 10 nM Tb-core with 20 nM F-σ70 after a 1-hour incubation at 22°C. The average value of A₅₂₀/A₄₉₀ for three replicates was determined and normalized to a no-treatment control with a buffer containing 50 mM Tris-HCl pH 7.9, 5% glycerol, and 100 mM NaCl. The error bars represent the normalized standard deviation for a sample size of 4. A) Common solvents (DMSO, ethanol, and methanol) were tested in a range of 0–50% (v/v). B) The non-ionic detergents TritonX-100 and Tween-20 were tested from 0–5% (v/v). C) Glycerol was tested from 2.5–50% (v/v). The minimum glycerol level (2.5%) was due to the glycerol in the buffer of the proteins. D) Bovine serum albumin (BSA) and MgCl₂ were tested from 0–1000 µg/mL and 0–500 mM, respectively.