Interaction of cyclodextrins with pyrene-modified polyacrylamide in a mixed solvent of water and dimethyl sulfoxide as studied by steady-state fluorescence

The interaction of beta- and gamma-cyclodextrins (beta-CD and gamma-CD, respectively) with polyacrylamide modified with pyrenyl (Py) residues (pAAmPy) was investigated in a mixed solvent of water and dimethyl sulfoxide ( DMSO) by steady-state fluorescence. In the absence of CD, the fluorescence spectra indicated that the formation of Py dimers became less favorable with increasing volume fraction of DMSO (x(DMSO)). The fluorescence spectra at varying x(DMSO) and CD concentrations indicated that beta-CD and gamma-CD included monomeric and dimeric Py residues, respectively. Using the fluorescence spectra, equilibrium constants of the formation of Py dimers and the complexation of beta-CD and gamma-CD with Py residues were roughly estimated based on simplified equilibrium schemes.