Figure 5:

Raman spectra of: (a) PEHA (100 mM)-ssDNA (3 mM) in solution (black trace); (b) PEHA (100 mM); and (c) ssDNA (3 mM). The red trace in (a) is the sum of the spectra shown in (c) and (d). The difference spectrum shown in (d) was calculated by subtracting the red trace from the black trace in (a). The fact that the experimentally measured spectrum in (a) shown in the black trace cannot be modeled as a linear combination of the ssDNA (c) and PEHA (b) spectra indicates binding is occurring between the two species. All spectra were normalized to the 2250 cm⁻¹ nitrile stretching band of acetonitrile, which was used as an internal intensity standard. The asterisk (*) symbol shows an artifact of subtracting out the spectral contribution of this nitrile stretching band.