Force-induced globule-coil transition in single polystyrene chains in water

Force induced globule-to-coil transitions have been studied in single homopolymer (polystyrene) chains in water using atomic force microscopy-based force spectroscopy. The conformational change showed signatures of a first-order-like transition. The characteristic plateau force observed in water disappears in the presence of 6 M guanidine hydrochloride (chaotropic salt), while in the presence of 1 M NaCl (kosmotropic salt) the plateau force is enhanced. These observations indicate that the characteristic plateau force observed may be governed by hydrophobic interactions.