Figure 2

Probing the interaction between different oligothymidines and BsCspB in absence and presence of a crowded environment by applying fluorescence spectroscopy in equilibrium. (A) The quench of intrinsic fluorescence of BsCspB has been determined for adding dT4 (colored in red, circles), dT5 (colored in orange, rectangles), and dT6 (colored in blue, triangles) under dilute (open symbols) and 300 g/L PEG1 conditions (closed symbols). (B) Intrinsic fluorescence quenching has been determined for adding dT5 in absence (colored in red, circles) and presence of 100 g/L Dex20 (colored in orange, rectangles), 200 g/L Dex20 (colored in cyan, triangles with tip to top), and 300 g/L Dex20 (colored in blue, triangles with tip to bottom). (C) Intrinsic fluorescence quenching has been determined for adding dT5 in absence (colored in red, circles) and presence of 300 g/L EG (colored in orange, rectangles) and 300 g/L glucose (colored in blue, triangles). (D) Intrinsic fluorescence quenching has been determined for adding dT5 in absence (colored in red, circles) and presence of 300 g/L PEG1 (colored in orange, rectangles) and 300 g/L Dex20 (colored in blue, triangles). All experiments have been performed at T = 298 K using c^BsCspB = 4 µM, except in (D) where c^BsCspB = 2.8 µM was used for c^PEG1 = 300 g/L. Equation (3) has been applied to perform numerical analysis of experimental data and the corresponding fitting functions are shown as continuous lines. (E) Binding affinity of dT5 to BsCspB in presence of c = 200 g/L of EG, glucose, PEG1, or Dex20. The horizontal line indicates binding affinity under dilute conditions. Associated data reporting on the binding affinity between oligothymidines and BsCspB are presented in Table 1 and Fig. S6A–E.