PEG and mPEG-anthracene induce DNA condensation and particle formation

In this study, we investigated the binding of DNA with poly(ethylene glycol) (PEG) of different sizes and compositions such as PEG 3350, PEG 6000, and mPEG-anthracene in aqueous solution at physiological conditions. The effects of size and composition on DNA aggregation and condensation as well as conformation were determined using Fourier transform infrared (FTIR), UV-visible, CD, fluorescence spectroscopic methods and atomic force microscopy (AFM). Structural analysis showed moderate complex formation for PEG 3350 and PEG 6000 and weaker interaction for mPE-anthracene-DNA adducts with both hydrophilic and hydrophobic contacts. The order of ± stability of the complexes formed is K_{PEG 6000} = 1.5 (±0.4) × 10 ⁴ M^-1 > K_{PEG 3350} = 7.9 (±1) × 10³ M^-1 > K_{mPEG-anthracene}= 3.6 (±0.8) × 10³ M^-1 with nearly 1 bound PEG molecule per DNA. No B-DNA conformational changes were observed, while DNA condensation and particle formation occurred at high PEG concentration.